Merging upstream version 1.45.3+dfsg.

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 4402 insertions, 0 deletions

diff --git a/src/fluent-bit/lib/libbacktrace-8602fda/dwarf.c b/src/fluent-bit/lib/libbacktrace-8602fda/dwarf.c
new file mode 100644
index 000000000..5b2724e6a
--- /dev/null
+++ b/src/fluent-bit/lib/libbacktrace-8602fda/dwarf.c
@@ -0,0 +1,4402 @@
+/* dwarf.c -- Get file/line information from DWARF for backtraces.
+   Copyright (C) 2012-2021 Free Software Foundation, Inc.
+   Written by Ian Lance Taylor, Google.
+
+Redistribution and use in source and binary forms, with or without
+modification, are permitted provided that the following conditions are
+met:
+
+    (1) Redistributions of source code must retain the above copyright
+    notice, this list of conditions and the following disclaimer.
+
+    (2) Redistributions in binary form must reproduce the above copyright
+    notice, this list of conditions and the following disclaimer in
+    the documentation and/or other materials provided with the
+    distribution.
+
+    (3) The name of the author may not be used to
+    endorse or promote products derived from this software without
+    specific prior written permission.
+
+THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
+IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
+WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+DISCLAIMED. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT,
+INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
+(INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
+STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING
+IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+POSSIBILITY OF SUCH DAMAGE.  */
+
+#include "config.h"
+
+#include <errno.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/types.h>
+
+#include "filenames.h"
+
+#include "backtrace.h"
+#include "internal.h"
+
+/* DWARF constants.  */
+
+enum dwarf_tag {
+  DW_TAG_entry_point = 0x3,
+  DW_TAG_compile_unit = 0x11,
+  DW_TAG_inlined_subroutine = 0x1d,
+  DW_TAG_subprogram = 0x2e,
+  DW_TAG_skeleton_unit = 0x4a,
+};
+
+enum dwarf_form {
+  DW_FORM_addr = 0x01,
+  DW_FORM_block2 = 0x03,
+  DW_FORM_block4 = 0x04,
+  DW_FORM_data2 = 0x05,
+  DW_FORM_data4 = 0x06,
+  DW_FORM_data8 = 0x07,
+  DW_FORM_string = 0x08,
+  DW_FORM_block = 0x09,
+  DW_FORM_block1 = 0x0a,
+  DW_FORM_data1 = 0x0b,
+  DW_FORM_flag = 0x0c,
+  DW_FORM_sdata = 0x0d,
+  DW_FORM_strp = 0x0e,
+  DW_FORM_udata = 0x0f,
+  DW_FORM_ref_addr = 0x10,
+  DW_FORM_ref1 = 0x11,
+  DW_FORM_ref2 = 0x12,
+  DW_FORM_ref4 = 0x13,
+  DW_FORM_ref8 = 0x14,
+  DW_FORM_ref_udata = 0x15,
+  DW_FORM_indirect = 0x16,
+  DW_FORM_sec_offset = 0x17,
+  DW_FORM_exprloc = 0x18,
+  DW_FORM_flag_present = 0x19,
+  DW_FORM_ref_sig8 = 0x20,
+  DW_FORM_strx = 0x1a,
+  DW_FORM_addrx = 0x1b,
+  DW_FORM_ref_sup4 = 0x1c,
+  DW_FORM_strp_sup = 0x1d,
+  DW_FORM_data16 = 0x1e,
+  DW_FORM_line_strp = 0x1f,
+  DW_FORM_implicit_const = 0x21,
+  DW_FORM_loclistx = 0x22,
+  DW_FORM_rnglistx = 0x23,
+  DW_FORM_ref_sup8 = 0x24,
+  DW_FORM_strx1 = 0x25,
+  DW_FORM_strx2 = 0x26,
+  DW_FORM_strx3 = 0x27,
+  DW_FORM_strx4 = 0x28,
+  DW_FORM_addrx1 = 0x29,
+  DW_FORM_addrx2 = 0x2a,
+  DW_FORM_addrx3 = 0x2b,
+  DW_FORM_addrx4 = 0x2c,
+  DW_FORM_GNU_addr_index = 0x1f01,
+  DW_FORM_GNU_str_index = 0x1f02,
+  DW_FORM_GNU_ref_alt = 0x1f20,
+  DW_FORM_GNU_strp_alt = 0x1f21
+};
+
+enum dwarf_attribute {
+  DW_AT_sibling = 0x01,
+  DW_AT_location = 0x02,
+  DW_AT_name = 0x03,
+  DW_AT_ordering = 0x09,
+  DW_AT_subscr_data = 0x0a,
+  DW_AT_byte_size = 0x0b,
+  DW_AT_bit_offset = 0x0c,
+  DW_AT_bit_size = 0x0d,
+  DW_AT_element_list = 0x0f,
+  DW_AT_stmt_list = 0x10,
+  DW_AT_low_pc = 0x11,
+  DW_AT_high_pc = 0x12,
+  DW_AT_language = 0x13,
+  DW_AT_member = 0x14,
+  DW_AT_discr = 0x15,
+  DW_AT_discr_value = 0x16,
+  DW_AT_visibility = 0x17,
+  DW_AT_import = 0x18,
+  DW_AT_string_length = 0x19,
+  DW_AT_common_reference = 0x1a,
+  DW_AT_comp_dir = 0x1b,
+  DW_AT_const_value = 0x1c,
+  DW_AT_containing_type = 0x1d,
+  DW_AT_default_value = 0x1e,
+  DW_AT_inline = 0x20,
+  DW_AT_is_optional = 0x21,
+  DW_AT_lower_bound = 0x22,
+  DW_AT_producer = 0x25,
+  DW_AT_prototyped = 0x27,
+  DW_AT_return_addr = 0x2a,
+  DW_AT_start_scope = 0x2c,
+  DW_AT_bit_stride = 0x2e,
+  DW_AT_upper_bound = 0x2f,
+  DW_AT_abstract_origin = 0x31,
+  DW_AT_accessibility = 0x32,
+  DW_AT_address_class = 0x33,
+  DW_AT_artificial = 0x34,
+  DW_AT_base_types = 0x35,
+  DW_AT_calling_convention = 0x36,
+  DW_AT_count = 0x37,
+  DW_AT_data_member_location = 0x38,
+  DW_AT_decl_column = 0x39,
+  DW_AT_decl_file = 0x3a,
+  DW_AT_decl_line = 0x3b,
+  DW_AT_declaration = 0x3c,
+  DW_AT_discr_list = 0x3d,
+  DW_AT_encoding = 0x3e,
+  DW_AT_external = 0x3f,
+  DW_AT_frame_base = 0x40,
+  DW_AT_friend = 0x41,
+  DW_AT_identifier_case = 0x42,
+  DW_AT_macro_info = 0x43,
+  DW_AT_namelist_items = 0x44,
+  DW_AT_priority = 0x45,
+  DW_AT_segment = 0x46,
+  DW_AT_specification = 0x47,
+  DW_AT_static_link = 0x48,
+  DW_AT_type = 0x49,
+  DW_AT_use_location = 0x4a,
+  DW_AT_variable_parameter = 0x4b,
+  DW_AT_virtuality = 0x4c,
+  DW_AT_vtable_elem_location = 0x4d,
+  DW_AT_allocated = 0x4e,
+  DW_AT_associated = 0x4f,
+  DW_AT_data_location = 0x50,
+  DW_AT_byte_stride = 0x51,
+  DW_AT_entry_pc = 0x52,
+  DW_AT_use_UTF8 = 0x53,
+  DW_AT_extension = 0x54,
+  DW_AT_ranges = 0x55,
+  DW_AT_trampoline = 0x56,
+  DW_AT_call_column = 0x57,
+  DW_AT_call_file = 0x58,
+  DW_AT_call_line = 0x59,
+  DW_AT_description = 0x5a,
+  DW_AT_binary_scale = 0x5b,
+  DW_AT_decimal_scale = 0x5c,
+  DW_AT_small = 0x5d,
+  DW_AT_decimal_sign = 0x5e,
+  DW_AT_digit_count = 0x5f,
+  DW_AT_picture_string = 0x60,
+  DW_AT_mutable = 0x61,
+  DW_AT_threads_scaled = 0x62,
+  DW_AT_explicit = 0x63,
+  DW_AT_object_pointer = 0x64,
+  DW_AT_endianity = 0x65,
+  DW_AT_elemental = 0x66,
+  DW_AT_pure = 0x67,
+  DW_AT_recursive = 0x68,
+  DW_AT_signature = 0x69,
+  DW_AT_main_subprogram = 0x6a,
+  DW_AT_data_bit_offset = 0x6b,
+  DW_AT_const_expr = 0x6c,
+  DW_AT_enum_class = 0x6d,
+  DW_AT_linkage_name = 0x6e,
+  DW_AT_string_length_bit_size = 0x6f,
+  DW_AT_string_length_byte_size = 0x70,
+  DW_AT_rank = 0x71,
+  DW_AT_str_offsets_base = 0x72,
+  DW_AT_addr_base = 0x73,
+  DW_AT_rnglists_base = 0x74,
+  DW_AT_dwo_name = 0x76,
+  DW_AT_reference = 0x77,
+  DW_AT_rvalue_reference = 0x78,
+  DW_AT_macros = 0x79,
+  DW_AT_call_all_calls = 0x7a,
+  DW_AT_call_all_source_calls = 0x7b,
+  DW_AT_call_all_tail_calls = 0x7c,
+  DW_AT_call_return_pc = 0x7d,
+  DW_AT_call_value = 0x7e,
+  DW_AT_call_origin = 0x7f,
+  DW_AT_call_parameter = 0x80,
+  DW_AT_call_pc = 0x81,
+  DW_AT_call_tail_call = 0x82,
+  DW_AT_call_target = 0x83,
+  DW_AT_call_target_clobbered = 0x84,
+  DW_AT_call_data_location = 0x85,
+  DW_AT_call_data_value = 0x86,
+  DW_AT_noreturn = 0x87,
+  DW_AT_alignment = 0x88,
+  DW_AT_export_symbols = 0x89,
+  DW_AT_deleted = 0x8a,
+  DW_AT_defaulted = 0x8b,
+  DW_AT_loclists_base = 0x8c,
+  DW_AT_lo_user = 0x2000,
+  DW_AT_hi_user = 0x3fff,
+  DW_AT_MIPS_fde = 0x2001,
+  DW_AT_MIPS_loop_begin = 0x2002,
+  DW_AT_MIPS_tail_loop_begin = 0x2003,
+  DW_AT_MIPS_epilog_begin = 0x2004,
+  DW_AT_MIPS_loop_unroll_factor = 0x2005,
+  DW_AT_MIPS_software_pipeline_depth = 0x2006,
+  DW_AT_MIPS_linkage_name = 0x2007,
+  DW_AT_MIPS_stride = 0x2008,
+  DW_AT_MIPS_abstract_name = 0x2009,
+  DW_AT_MIPS_clone_origin = 0x200a,
+  DW_AT_MIPS_has_inlines = 0x200b,
+  DW_AT_HP_block_index = 0x2000,
+  DW_AT_HP_unmodifiable = 0x2001,
+  DW_AT_HP_prologue = 0x2005,
+  DW_AT_HP_epilogue = 0x2008,
+  DW_AT_HP_actuals_stmt_list = 0x2010,
+  DW_AT_HP_proc_per_section = 0x2011,
+  DW_AT_HP_raw_data_ptr = 0x2012,
+  DW_AT_HP_pass_by_reference = 0x2013,
+  DW_AT_HP_opt_level = 0x2014,
+  DW_AT_HP_prof_version_id = 0x2015,
+  DW_AT_HP_opt_flags = 0x2016,
+  DW_AT_HP_cold_region_low_pc = 0x2017,
+  DW_AT_HP_cold_region_high_pc = 0x2018,
+  DW_AT_HP_all_variables_modifiable = 0x2019,
+  DW_AT_HP_linkage_name = 0x201a,
+  DW_AT_HP_prof_flags = 0x201b,
+  DW_AT_HP_unit_name = 0x201f,
+  DW_AT_HP_unit_size = 0x2020,
+  DW_AT_HP_widened_byte_size = 0x2021,
+  DW_AT_HP_definition_points = 0x2022,
+  DW_AT_HP_default_location = 0x2023,
+  DW_AT_HP_is_result_param = 0x2029,
+  DW_AT_sf_names = 0x2101,
+  DW_AT_src_info = 0x2102,
+  DW_AT_mac_info = 0x2103,
+  DW_AT_src_coords = 0x2104,
+  DW_AT_body_begin = 0x2105,
+  DW_AT_body_end = 0x2106,
+  DW_AT_GNU_vector = 0x2107,
+  DW_AT_GNU_guarded_by = 0x2108,
+  DW_AT_GNU_pt_guarded_by = 0x2109,
+  DW_AT_GNU_guarded = 0x210a,
+  DW_AT_GNU_pt_guarded = 0x210b,
+  DW_AT_GNU_locks_excluded = 0x210c,
+  DW_AT_GNU_exclusive_locks_required = 0x210d,
+  DW_AT_GNU_shared_locks_required = 0x210e,
+  DW_AT_GNU_odr_signature = 0x210f,
+  DW_AT_GNU_template_name = 0x2110,
+  DW_AT_GNU_call_site_value = 0x2111,
+  DW_AT_GNU_call_site_data_value = 0x2112,
+  DW_AT_GNU_call_site_target = 0x2113,
+  DW_AT_GNU_call_site_target_clobbered = 0x2114,
+  DW_AT_GNU_tail_call = 0x2115,
+  DW_AT_GNU_all_tail_call_sites = 0x2116,
+  DW_AT_GNU_all_call_sites = 0x2117,
+  DW_AT_GNU_all_source_call_sites = 0x2118,
+  DW_AT_GNU_macros = 0x2119,
+  DW_AT_GNU_deleted = 0x211a,
+  DW_AT_GNU_dwo_name = 0x2130,
+  DW_AT_GNU_dwo_id = 0x2131,
+  DW_AT_GNU_ranges_base = 0x2132,
+  DW_AT_GNU_addr_base = 0x2133,
+  DW_AT_GNU_pubnames = 0x2134,
+  DW_AT_GNU_pubtypes = 0x2135,
+  DW_AT_GNU_discriminator = 0x2136,
+  DW_AT_GNU_locviews = 0x2137,
+  DW_AT_GNU_entry_view = 0x2138,
+  DW_AT_VMS_rtnbeg_pd_address = 0x2201,
+  DW_AT_use_GNAT_descriptive_type = 0x2301,
+  DW_AT_GNAT_descriptive_type = 0x2302,
+  DW_AT_GNU_numerator = 0x2303,
+  DW_AT_GNU_denominator = 0x2304,
+  DW_AT_GNU_bias = 0x2305,
+  DW_AT_upc_threads_scaled = 0x3210,
+  DW_AT_PGI_lbase = 0x3a00,
+  DW_AT_PGI_soffset = 0x3a01,
+  DW_AT_PGI_lstride = 0x3a02,
+  DW_AT_APPLE_optimized = 0x3fe1,
+  DW_AT_APPLE_flags = 0x3fe2,
+  DW_AT_APPLE_isa = 0x3fe3,
+  DW_AT_APPLE_block = 0x3fe4,
+  DW_AT_APPLE_major_runtime_vers = 0x3fe5,
+  DW_AT_APPLE_runtime_class = 0x3fe6,
+  DW_AT_APPLE_omit_frame_ptr = 0x3fe7,
+  DW_AT_APPLE_property_name = 0x3fe8,
+  DW_AT_APPLE_property_getter = 0x3fe9,
+  DW_AT_APPLE_property_setter = 0x3fea,
+  DW_AT_APPLE_property_attribute = 0x3feb,
+  DW_AT_APPLE_objc_complete_type = 0x3fec,
+  DW_AT_APPLE_property = 0x3fed
+};
+
+enum dwarf_line_number_op {
+  DW_LNS_extended_op = 0x0,
+  DW_LNS_copy = 0x1,
+  DW_LNS_advance_pc = 0x2,
+  DW_LNS_advance_line = 0x3,
+  DW_LNS_set_file = 0x4,
+  DW_LNS_set_column = 0x5,
+  DW_LNS_negate_stmt = 0x6,
+  DW_LNS_set_basic_block = 0x7,
+  DW_LNS_const_add_pc = 0x8,
+  DW_LNS_fixed_advance_pc = 0x9,
+  DW_LNS_set_prologue_end = 0xa,
+  DW_LNS_set_epilogue_begin = 0xb,
+  DW_LNS_set_isa = 0xc,
+};
+
+enum dwarf_extended_line_number_op {
+  DW_LNE_end_sequence = 0x1,
+  DW_LNE_set_address = 0x2,
+  DW_LNE_define_file = 0x3,
+  DW_LNE_set_discriminator = 0x4,
+};
+
+enum dwarf_line_number_content_type {
+  DW_LNCT_path = 0x1,
+  DW_LNCT_directory_index = 0x2,
+  DW_LNCT_timestamp = 0x3,
+  DW_LNCT_size = 0x4,
+  DW_LNCT_MD5 = 0x5,
+  DW_LNCT_lo_user = 0x2000,
+  DW_LNCT_hi_user = 0x3fff
+};
+
+enum dwarf_range_list_entry {
+  DW_RLE_end_of_list = 0x00,
+  DW_RLE_base_addressx = 0x01,
+  DW_RLE_startx_endx = 0x02,
+  DW_RLE_startx_length = 0x03,
+  DW_RLE_offset_pair = 0x04,
+  DW_RLE_base_address = 0x05,
+  DW_RLE_start_end = 0x06,
+  DW_RLE_start_length = 0x07
+};
+
+enum dwarf_unit_type {
+  DW_UT_compile = 0x01,
+  DW_UT_type = 0x02,
+  DW_UT_partial = 0x03,
+  DW_UT_skeleton = 0x04,
+  DW_UT_split_compile = 0x05,
+  DW_UT_split_type = 0x06,
+  DW_UT_lo_user = 0x80,
+  DW_UT_hi_user = 0xff
+};
+
+#if !defined(HAVE_DECL_STRNLEN) || !HAVE_DECL_STRNLEN
+
+/* If strnlen is not declared, provide our own version.  */
+
+static size_t
+xstrnlen (const char *s, size_t maxlen)
+{
+  size_t i;
+
+  for (i = 0; i < maxlen; ++i)
+    if (s[i] == '\0')
+      break;
+  return i;
+}
+
+#define strnlen xstrnlen
+
+#endif
+
+/* A buffer to read DWARF info.  */
+
+struct dwarf_buf
+{
+  /* Buffer name for error messages.  */
+  const char *name;
+  /* Start of the buffer.  */
+  const unsigned char *start;
+  /* Next byte to read.  */
+  const unsigned char *buf;
+  /* The number of bytes remaining.  */
+  size_t left;
+  /* Whether the data is big-endian.  */
+  int is_bigendian;
+  /* Error callback routine.  */
+  backtrace_error_callback error_callback;
+  /* Data for error_callback.  */
+  void *data;
+  /* Non-zero if we've reported an underflow error.  */
+  int reported_underflow;
+};
+
+/* A single attribute in a DWARF abbreviation.  */
+
+struct attr
+{
+  /* The attribute name.  */
+  enum dwarf_attribute name;
+  /* The attribute form.  */
+  enum dwarf_form form;
+  /* The attribute value, for DW_FORM_implicit_const.  */
+  int64_t val;
+};
+
+/* A single DWARF abbreviation.  */
+
+struct abbrev
+{
+  /* The abbrev code--the number used to refer to the abbrev.  */
+  uint64_t code;
+  /* The entry tag.  */
+  enum dwarf_tag tag;
+  /* Non-zero if this abbrev has child entries.  */
+  int has_children;
+  /* The number of attributes.  */
+  size_t num_attrs;
+  /* The attributes.  */
+  struct attr *attrs;
+};
+
+/* The DWARF abbreviations for a compilation unit.  This structure
+   only exists while reading the compilation unit.  Most DWARF readers
+   seem to a hash table to map abbrev ID's to abbrev entries.
+   However, we primarily care about GCC, and GCC simply issues ID's in
+   numerical order starting at 1.  So we simply keep a sorted vector,
+   and try to just look up the code.  */
+
+struct abbrevs
+{
+  /* The number of abbrevs in the vector.  */
+  size_t num_abbrevs;
+  /* The abbrevs, sorted by the code field.  */
+  struct abbrev *abbrevs;
+};
+
+/* The different kinds of attribute values.  */
+
+enum attr_val_encoding
+{
+  /* No attribute value.  */
+  ATTR_VAL_NONE,
+  /* An address.  */
+  ATTR_VAL_ADDRESS,
+  /* An index into the .debug_addr section, whose value is relative to
+   * the DW_AT_addr_base attribute of the compilation unit.  */
+  ATTR_VAL_ADDRESS_INDEX,
+  /* A unsigned integer.  */
+  ATTR_VAL_UINT,
+  /* A sigd integer.  */
+  ATTR_VAL_SINT,
+  /* A string.  */
+  ATTR_VAL_STRING,
+  /* An index into the .debug_str_offsets section.  */
+  ATTR_VAL_STRING_INDEX,
+  /* An offset to other data in the containing unit.  */
+  ATTR_VAL_REF_UNIT,
+  /* An offset to other data within the .debug_info section.  */
+  ATTR_VAL_REF_INFO,
+  /* An offset to other data within the alt .debug_info section.  */
+  ATTR_VAL_REF_ALT_INFO,
+  /* An offset to data in some other section.  */
+  ATTR_VAL_REF_SECTION,
+  /* A type signature.  */
+  ATTR_VAL_REF_TYPE,
+  /* An index into the .debug_rnglists section.  */
+  ATTR_VAL_RNGLISTS_INDEX,
+  /* A block of data (not represented).  */
+  ATTR_VAL_BLOCK,
+  /* An expression (not represented).  */
+  ATTR_VAL_EXPR,
+};
+
+/* An attribute value.  */
+
+struct attr_val
+{
+  /* How the value is stored in the field u.  */
+  enum attr_val_encoding encoding;
+  union
+  {
+    /* ATTR_VAL_ADDRESS*, ATTR_VAL_UINT, ATTR_VAL_REF*.  */
+    uint64_t uint;
+    /* ATTR_VAL_SINT.  */
+    int64_t sint;
+    /* ATTR_VAL_STRING.  */
+    const char *string;
+    /* ATTR_VAL_BLOCK not stored.  */
+  } u;
+};
+
+/* The line number program header.  */
+
+struct line_header
+{
+  /* The version of the line number information.  */
+  int version;
+  /* Address size.  */
+  int addrsize;
+  /* The minimum instruction length.  */
+  unsigned int min_insn_len;
+  /* The maximum number of ops per instruction.  */
+  unsigned int max_ops_per_insn;
+  /* The line base for special opcodes.  */
+  int line_base;
+  /* The line range for special opcodes.  */
+  unsigned int line_range;
+  /* The opcode base--the first special opcode.  */
+  unsigned int opcode_base;
+  /* Opcode lengths, indexed by opcode - 1.  */
+  const unsigned char *opcode_lengths;
+  /* The number of directory entries.  */
+  size_t dirs_count;
+  /* The directory entries.  */
+  const char **dirs;
+  /* The number of filenames.  */
+  size_t filenames_count;
+  /* The filenames.  */
+  const char **filenames;
+};
+
+/* A format description from a line header.  */
+
+struct line_header_format
+{
+  int lnct;		/* LNCT code.  */
+  enum dwarf_form form;	/* Form of entry data.  */
+};
+
+/* Map a single PC value to a file/line.  We will keep a vector of
+   these sorted by PC value.  Each file/line will be correct from the
+   PC up to the PC of the next entry if there is one.  We allocate one
+   extra entry at the end so that we can use bsearch.  */
+
+struct line
+{
+  /* PC.  */
+  uintptr_t pc;
+  /* File name.  Many entries in the array are expected to point to
+     the same file name.  */
+  const char *filename;
+  /* Line number.  */
+  int lineno;
+  /* Index of the object in the original array read from the DWARF
+     section, before it has been sorted.  The index makes it possible
+     to use Quicksort and maintain stability.  */
+  int idx;
+};
+
+/* A growable vector of line number information.  This is used while
+   reading the line numbers.  */
+
+struct line_vector
+{
+  /* Memory.  This is an array of struct line.  */
+  struct backtrace_vector vec;
+  /* Number of valid mappings.  */
+  size_t count;
+};
+
+/* A function described in the debug info.  */
+
+struct function
+{
+  /* The name of the function.  */
+  const char *name;
+  /* If this is an inlined function, the filename of the call
+     site.  */
+  const char *caller_filename;
+  /* If this is an inlined function, the line number of the call
+     site.  */
+  int caller_lineno;
+  /* Map PC ranges to inlined functions.  */
+  struct function_addrs *function_addrs;
+  size_t function_addrs_count;
+};
+
+/* An address range for a function.  This maps a PC value to a
+   specific function.  */
+
+struct function_addrs
+{
+  /* Range is LOW <= PC < HIGH.  */
+  uint64_t low;
+  uint64_t high;
+  /* Function for this address range.  */
+  struct function *function;
+};
+
+/* A growable vector of function address ranges.  */
+
+struct function_vector
+{
+  /* Memory.  This is an array of struct function_addrs.  */
+  struct backtrace_vector vec;
+  /* Number of address ranges present.  */
+  size_t count;
+};
+
+/* A DWARF compilation unit.  This only holds the information we need
+   to map a PC to a file and line.  */
+
+struct unit
+{
+  /* The first entry for this compilation unit.  */
+  const unsigned char *unit_data;
+  /* The length of the data for this compilation unit.  */
+  size_t unit_data_len;
+  /* The offset of UNIT_DATA from the start of the information for
+     this compilation unit.  */
+  size_t unit_data_offset;
+  /* Offset of the start of the compilation unit from the start of the
+     .debug_info section.  */
+  size_t low_offset;
+  /* Offset of the end of the compilation unit from the start of the
+     .debug_info section.  */
+  size_t high_offset;
+  /* DWARF version.  */
+  int version;
+  /* Whether unit is DWARF64.  */
+  int is_dwarf64;
+  /* Address size.  */
+  int addrsize;
+  /* Offset into line number information.  */
+  off_t lineoff;
+  /* Offset of compilation unit in .debug_str_offsets.  */
+  uint64_t str_offsets_base;
+  /* Offset of compilation unit in .debug_addr.  */
+  uint64_t addr_base;
+  /* Offset of compilation unit in .debug_rnglists.  */
+  uint64_t rnglists_base;
+  /* Primary source file.  */
+  const char *filename;
+  /* Compilation command working directory.  */
+  const char *comp_dir;
+  /* Absolute file name, only set if needed.  */
+  const char *abs_filename;
+  /* The abbreviations for this unit.  */
+  struct abbrevs abbrevs;
+
+  /* The fields above this point are read in during initialization and
+     may be accessed freely.  The fields below this point are read in
+     as needed, and therefore require care, as different threads may
+     try to initialize them simultaneously.  */
+
+  /* PC to line number mapping.  This is NULL if the values have not
+     been read.  This is (struct line *) -1 if there was an error
+     reading the values.  */
+  struct line *lines;
+  /* Number of entries in lines.  */
+  size_t lines_count;
+  /* PC ranges to function.  */
+  struct function_addrs *function_addrs;
+  size_t function_addrs_count;
+};
+
+/* An address range for a compilation unit.  This maps a PC value to a
+   specific compilation unit.  Note that we invert the representation
+   in DWARF: instead of listing the units and attaching a list of
+   ranges, we list the ranges and have each one point to the unit.
+   This lets us do a binary search to find the unit.  */
+
+struct unit_addrs
+{
+  /* Range is LOW <= PC < HIGH.  */
+  uint64_t low;
+  uint64_t high;
+  /* Compilation unit for this address range.  */
+  struct unit *u;
+};
+
+/* A growable vector of compilation unit address ranges.  */
+
+struct unit_addrs_vector
+{
+  /* Memory.  This is an array of struct unit_addrs.  */
+  struct backtrace_vector vec;
+  /* Number of address ranges present.  */
+  size_t count;
+};
+
+/* A growable vector of compilation unit pointer.  */
+
+struct unit_vector
+{
+  struct backtrace_vector vec;
+  size_t count;
+};
+
+/* The information we need to map a PC to a file and line.  */
+
+struct dwarf_data
+{
+  /* The data for the next file we know about.  */
+  struct dwarf_data *next;
+  /* The data for .gnu_debugaltlink.  */
+  struct dwarf_data *altlink;
+  /* The base address for this file.  */
+  uintptr_t base_address;
+  /* A sorted list of address ranges.  */
+  struct unit_addrs *addrs;
+  /* Number of address ranges in list.  */
+  size_t addrs_count;
+  /* A sorted list of units.  */
+  struct unit **units;
+  /* Number of units in the list.  */
+  size_t units_count;
+  /* The unparsed DWARF debug data.  */
+  struct dwarf_sections dwarf_sections;
+  /* Whether the data is big-endian or not.  */
+  int is_bigendian;
+  /* A vector used for function addresses.  We keep this here so that
+     we can grow the vector as we read more functions.  */
+  struct function_vector fvec;
+};
+
+/* Report an error for a DWARF buffer.  */
+
+static void
+dwarf_buf_error (struct dwarf_buf *buf, const char *msg, int errnum)
+{
+  char b[200];
+
+  snprintf (b, sizeof b, "%s in %s at %d",
+	    msg, buf->name, (int) (buf->buf - buf->start));
+  buf->error_callback (buf->data, b, errnum);
+}
+
+/* Require at least COUNT bytes in BUF.  Return 1 if all is well, 0 on
+   error.  */
+
+static int
+require (struct dwarf_buf *buf, size_t count)
+{
+  if (buf->left >= count)
+    return 1;
+
+  if (!buf->reported_underflow)
+    {
+      dwarf_buf_error (buf, "DWARF underflow", 0);
+      buf->reported_underflow = 1;
+    }
+
+  return 0;
+}
+
+/* Advance COUNT bytes in BUF.  Return 1 if all is well, 0 on
+   error.  */
+
+static int
+advance (struct dwarf_buf *buf, size_t count)
+{
+  if (!require (buf, count))
+    return 0;
+  buf->buf += count;
+  buf->left -= count;
+  return 1;
+}
+
+/* Read one zero-terminated string from BUF and advance past the string.  */
+
+static const char *
+read_string (struct dwarf_buf *buf)
+{
+  const char *p = (const char *)buf->buf;
+  size_t len = strnlen (p, buf->left);
+
+  /* - If len == left, we ran out of buffer before finding the zero terminator.
+       Generate an error by advancing len + 1.
+     - If len < left, advance by len + 1 to skip past the zero terminator.  */
+  size_t count = len + 1;
+
+  if (!advance (buf, count))
+    return NULL;
+
+  return p;
+}
+
+/* Read one byte from BUF and advance 1 byte.  */
+
+static unsigned char
+read_byte (struct dwarf_buf *buf)
+{
+  const unsigned char *p = buf->buf;
+
+  if (!advance (buf, 1))
+    return 0;
+  return p[0];
+}
+
+/* Read a signed char from BUF and advance 1 byte.  */
+
+static signed char
+read_sbyte (struct dwarf_buf *buf)
+{
+  const unsigned char *p = buf->buf;
+
+  if (!advance (buf, 1))
+    return 0;
+  return (*p ^ 0x80) - 0x80;
+}
+
+/* Read a uint16 from BUF and advance 2 bytes.  */
+
+static uint16_t
+read_uint16 (struct dwarf_buf *buf)
+{
+  const unsigned char *p = buf->buf;
+
+  if (!advance (buf, 2))
+    return 0;
+  if (buf->is_bigendian)
+    return ((uint16_t) p[0] << 8) | (uint16_t) p[1];
+  else
+    return ((uint16_t) p[1] << 8) | (uint16_t) p[0];
+}
+
+/* Read a 24 bit value from BUF and advance 3 bytes.  */
+
+static uint32_t
+read_uint24 (struct dwarf_buf *buf)
+{
+  const unsigned char *p = buf->buf;
+
+  if (!advance (buf, 3))
+    return 0;
+  if (buf->is_bigendian)
+    return (((uint32_t) p[0] << 16) | ((uint32_t) p[1] << 8)
+	    | (uint32_t) p[2]);
+  else
+    return (((uint32_t) p[2] << 16) | ((uint32_t) p[1] << 8)
+	    | (uint32_t) p[0]);
+}
+
+/* Read a uint32 from BUF and advance 4 bytes.  */
+
+static uint32_t
+read_uint32 (struct dwarf_buf *buf)
+{
+  const unsigned char *p = buf->buf;
+
+  if (!advance (buf, 4))
+    return 0;
+  if (buf->is_bigendian)
+    return (((uint32_t) p[0] << 24) | ((uint32_t) p[1] << 16)
+	    | ((uint32_t) p[2] << 8) | (uint32_t) p[3]);
+  else
+    return (((uint32_t) p[3] << 24) | ((uint32_t) p[2] << 16)
+	    | ((uint32_t) p[1] << 8) | (uint32_t) p[0]);
+}
+
+/* Read a uint64 from BUF and advance 8 bytes.  */
+
+static uint64_t
+read_uint64 (struct dwarf_buf *buf)
+{
+  const unsigned char *p = buf->buf;
+
+  if (!advance (buf, 8))
+    return 0;
+  if (buf->is_bigendian)
+    return (((uint64_t) p[0] << 56) | ((uint64_t) p[1] << 48)
+	    | ((uint64_t) p[2] << 40) | ((uint64_t) p[3] << 32)
+	    | ((uint64_t) p[4] << 24) | ((uint64_t) p[5] << 16)
+	    | ((uint64_t) p[6] << 8) | (uint64_t) p[7]);
+  else
+    return (((uint64_t) p[7] << 56) | ((uint64_t) p[6] << 48)
+	    | ((uint64_t) p[5] << 40) | ((uint64_t) p[4] << 32)
+	    | ((uint64_t) p[3] << 24) | ((uint64_t) p[2] << 16)
+	    | ((uint64_t) p[1] << 8) | (uint64_t) p[0]);
+}
+
+/* Read an offset from BUF and advance the appropriate number of
+   bytes.  */
+
+static uint64_t
+read_offset (struct dwarf_buf *buf, int is_dwarf64)
+{
+  if (is_dwarf64)
+    return read_uint64 (buf);
+  else
+    return read_uint32 (buf);
+}
+
+/* Read an address from BUF and advance the appropriate number of
+   bytes.  */
+
+static uint64_t
+read_address (struct dwarf_buf *buf, int addrsize)
+{
+  switch (addrsize)
+    {
+    case 1:
+      return read_byte (buf);
+    case 2:
+      return read_uint16 (buf);
+    case 4:
+      return read_uint32 (buf);
+    case 8:
+      return read_uint64 (buf);
+    default:
+      dwarf_buf_error (buf, "unrecognized address size", 0);
+      return 0;
+    }
+}
+
+/* Return whether a value is the highest possible address, given the
+   address size.  */
+
+static int
+is_highest_address (uint64_t address, int addrsize)
+{
+  switch (addrsize)
+    {
+    case 1:
+      return address == (unsigned char) -1;
+    case 2:
+      return address == (uint16_t) -1;
+    case 4:
+      return address == (uint32_t) -1;
+    case 8:
+      return address == (uint64_t) -1;
+    default:
+      return 0;
+    }
+}
+
+/* Read an unsigned LEB128 number.  */
+
+static uint64_t
+read_uleb128 (struct dwarf_buf *buf)
+{
+  uint64_t ret;
+  unsigned int shift;
+  int overflow;
+  unsigned char b;
+
+  ret = 0;
+  shift = 0;
+  overflow = 0;
+  do
+    {
+      const unsigned char *p;
+
+      p = buf->buf;
+      if (!advance (buf, 1))
+	return 0;
+      b = *p;
+      if (shift < 64)
+	ret |= ((uint64_t) (b & 0x7f)) << shift;
+      else if (!overflow)
+	{
+	  dwarf_buf_error (buf, "LEB128 overflows uint64_t", 0);
+	  overflow = 1;
+	}
+      shift += 7;
+    }
+  while ((b & 0x80) != 0);
+
+  return ret;
+}
+
+/* Read a signed LEB128 number.  */
+
+static int64_t
+read_sleb128 (struct dwarf_buf *buf)
+{
+  uint64_t val;
+  unsigned int shift;
+  int overflow;
+  unsigned char b;
+
+  val = 0;
+  shift = 0;
+  overflow = 0;
+  do
+    {
+      const unsigned char *p;
+
+      p = buf->buf;
+      if (!advance (buf, 1))
+	return 0;
+      b = *p;
+      if (shift < 64)
+	val |= ((uint64_t) (b & 0x7f)) << shift;
+      else if (!overflow)
+	{
+	  dwarf_buf_error (buf, "signed LEB128 overflows uint64_t", 0);
+	  overflow = 1;
+	}
+      shift += 7;
+    }
+  while ((b & 0x80) != 0);
+
+  if ((b & 0x40) != 0 && shift < 64)
+    val |= ((uint64_t) -1) << shift;
+
+  return (int64_t) val;
+}
+
+/* Return the length of an LEB128 number.  */
+
+static size_t
+leb128_len (const unsigned char *p)
+{
+  size_t ret;
+
+  ret = 1;
+  while ((*p & 0x80) != 0)
+    {
+      ++p;
+      ++ret;
+    }
+  return ret;
+}
+
+/* Read initial_length from BUF and advance the appropriate number of bytes.  */
+
+static uint64_t
+read_initial_length (struct dwarf_buf *buf, int *is_dwarf64)
+{
+  uint64_t len;
+
+  len = read_uint32 (buf);
+  if (len == 0xffffffff)
+    {
+      len = read_uint64 (buf);
+      *is_dwarf64 = 1;
+    }
+  else
+    *is_dwarf64 = 0;
+
+  return len;
+}
+
+/* Free an abbreviations structure.  */
+
+static void
+free_abbrevs (struct backtrace_state *state, struct abbrevs *abbrevs,
+	      backtrace_error_callback error_callback, void *data)
+{
+  size_t i;
+
+  for (i = 0; i < abbrevs->num_abbrevs; ++i)
+    backtrace_free (state, abbrevs->abbrevs[i].attrs,
+		    abbrevs->abbrevs[i].num_attrs * sizeof (struct attr),
+		    error_callback, data);
+  backtrace_free (state, abbrevs->abbrevs,
+		  abbrevs->num_abbrevs * sizeof (struct abbrev),
+		  error_callback, data);
+  abbrevs->num_abbrevs = 0;
+  abbrevs->abbrevs = NULL;
+}
+
+/* Read an attribute value.  Returns 1 on success, 0 on failure.  If
+   the value can be represented as a uint64_t, sets *VAL and sets
+   *IS_VALID to 1.  We don't try to store the value of other attribute
+   forms, because we don't care about them.  */
+
+static int
+read_attribute (enum dwarf_form form, uint64_t implicit_val,
+		struct dwarf_buf *buf, int is_dwarf64, int version,
+		int addrsize, const struct dwarf_sections *dwarf_sections,
+		struct dwarf_data *altlink, struct attr_val *val)
+{
+  /* Avoid warnings about val.u.FIELD may be used uninitialized if
+     this function is inlined.  The warnings aren't valid but can
+     occur because the different fields are set and used
+     conditionally.  */
+  memset (val, 0, sizeof *val);
+
+  switch (form)
+    {
+    case DW_FORM_addr:
+      val->encoding = ATTR_VAL_ADDRESS;
+      val->u.uint = read_address (buf, addrsize);
+      return 1;
+    case DW_FORM_block2:
+      val->encoding = ATTR_VAL_BLOCK;
+      return advance (buf, read_uint16 (buf));
+    case DW_FORM_block4:
+      val->encoding = ATTR_VAL_BLOCK;
+      return advance (buf, read_uint32 (buf));
+    case DW_FORM_data2:
+      val->encoding = ATTR_VAL_UINT;
+      val->u.uint = read_uint16 (buf);
+      return 1;
+    case DW_FORM_data4:
+      val->encoding = ATTR_VAL_UINT;
+      val->u.uint = read_uint32 (buf);
+      return 1;
+    case DW_FORM_data8:
+      val->encoding = ATTR_VAL_UINT;
+      val->u.uint = read_uint64 (buf);
+      return 1;
+    case DW_FORM_data16:
+      val->encoding = ATTR_VAL_BLOCK;
+      return advance (buf, 16);
+    case DW_FORM_string:
+      val->encoding = ATTR_VAL_STRING;
+      val->u.string = read_string (buf);
+      return val->u.string == NULL ? 0 : 1;
+    case DW_FORM_block:
+      val->encoding = ATTR_VAL_BLOCK;
+      return advance (buf, read_uleb128 (buf));
+    case DW_FORM_block1:
+      val->encoding = ATTR_VAL_BLOCK;
+      return advance (buf, read_byte (buf));
+    case DW_FORM_data1:
+      val->encoding = ATTR_VAL_UINT;
+      val->u.uint = read_byte (buf);
+      return 1;
+    case DW_FORM_flag:
+      val->encoding = ATTR_VAL_UINT;
+      val->u.uint = read_byte (buf);
+      return 1;
+    case DW_FORM_sdata:
+      val->encoding = ATTR_VAL_SINT;
+      val->u.sint = read_sleb128 (buf);
+      return 1;
+    case DW_FORM_strp:
+      {
+	uint64_t offset;
+
+	offset = read_offset (buf, is_dwarf64);
+	if (offset >= dwarf_sections->size[DEBUG_STR])
+	  {
+	    dwarf_buf_error (buf, "DW_FORM_strp out of range", 0);
+	    return 0;
+	  }
+	val->encoding = ATTR_VAL_STRING;
+	val->u.string =
+	  (const char *) dwarf_sections->data[DEBUG_STR] + offset;
+	return 1;
+      }
+    case DW_FORM_line_strp:
+      {
+	uint64_t offset;
+
+	offset = read_offset (buf, is_dwarf64);
+	if (offset >= dwarf_sections->size[DEBUG_LINE_STR])
+	  {
+	    dwarf_buf_error (buf, "DW_FORM_line_strp out of range", 0);
+	    return 0;
+	  }
+	val->encoding = ATTR_VAL_STRING;
+	val->u.string =
+	  (const char *) dwarf_sections->data[DEBUG_LINE_STR] + offset;
+	return 1;
+      }
+    case DW_FORM_udata:
+      val->encoding = ATTR_VAL_UINT;
+      val->u.uint = read_uleb128 (buf);
+      return 1;
+    case DW_FORM_ref_addr:
+      val->encoding = ATTR_VAL_REF_INFO;
+      if (version == 2)
+	val->u.uint = read_address (buf, addrsize);
+      else
+	val->u.uint = read_offset (buf, is_dwarf64);
+      return 1;
+    case DW_FORM_ref1:
+      val->encoding = ATTR_VAL_REF_UNIT;
+      val->u.uint = read_byte (buf);
+      return 1;
+    case DW_FORM_ref2:
+      val->encoding = ATTR_VAL_REF_UNIT;
+      val->u.uint = read_uint16 (buf);
+      return 1;
+    case DW_FORM_ref4:
+      val->encoding = ATTR_VAL_REF_UNIT;
+      val->u.uint = read_uint32 (buf);
+      return 1;
+    case DW_FORM_ref8:
+      val->encoding = ATTR_VAL_REF_UNIT;
+      val->u.uint = read_uint64 (buf);
+      return 1;
+    case DW_FORM_ref_udata:
+      val->encoding = ATTR_VAL_REF_UNIT;
+      val->u.uint = read_uleb128 (buf);
+      return 1;
+    case DW_FORM_indirect:
+      {
+	uint64_t form;
+
+	form = read_uleb128 (buf);
+	if (form == DW_FORM_implicit_const)
+	  {
+	    dwarf_buf_error (buf,
+			     "DW_FORM_indirect to DW_FORM_implicit_const",
+			     0);
+	    return 0;
+	  }
+	return read_attribute ((enum dwarf_form) form, 0, buf, is_dwarf64,
+			       version, addrsize, dwarf_sections, altlink,
+			       val);
+      }
+    case DW_FORM_sec_offset:
+      val->encoding = ATTR_VAL_REF_SECTION;
+      val->u.uint = read_offset (buf, is_dwarf64);
+      return 1;
+    case DW_FORM_exprloc:
+      val->encoding = ATTR_VAL_EXPR;
+      return advance (buf, read_uleb128 (buf));
+    case DW_FORM_flag_present:
+      val->encoding = ATTR_VAL_UINT;
+      val->u.uint = 1;
+      return 1;
+    case DW_FORM_ref_sig8:
+      val->encoding = ATTR_VAL_REF_TYPE;
+      val->u.uint = read_uint64 (buf);
+      return 1;
+    case DW_FORM_strx: case DW_FORM_strx1: case DW_FORM_strx2:
+    case DW_FORM_strx3: case DW_FORM_strx4:
+      {
+	uint64_t offset;
+
+	switch (form)
+	  {
+	  case DW_FORM_strx:
+	    offset = read_uleb128 (buf);
+	    break;
+	  case DW_FORM_strx1:
+	    offset = read_byte (buf);
+	    break;
+	  case DW_FORM_strx2:
+	    offset = read_uint16 (buf);
+	    break;
+	  case DW_FORM_strx3:
+	    offset = read_uint24 (buf);
+	    break;
+	  case DW_FORM_strx4:
+	    offset = read_uint32 (buf);
+	    break;
+	  default:
+	    /* This case can't happen.  */
+	    return 0;
+	  }
+	val->encoding = ATTR_VAL_STRING_INDEX;
+	val->u.uint = offset;
+	return 1;
+      }
+    case DW_FORM_addrx: case DW_FORM_addrx1: case DW_FORM_addrx2:
+    case DW_FORM_addrx3: case DW_FORM_addrx4:
+      {
+	uint64_t offset;
+
+	switch (form)
+	  {
+	  case DW_FORM_addrx:
+	    offset = read_uleb128 (buf);
+	    break;
+	  case DW_FORM_addrx1:
+	    offset = read_byte (buf);
+	    break;
+	  case DW_FORM_addrx2:
+	    offset = read_uint16 (buf);
+	    break;
+	  case DW_FORM_addrx3:
+	    offset = read_uint24 (buf);
+	    break;
+	  case DW_FORM_addrx4:
+	    offset = read_uint32 (buf);
+	    break;
+	  default:
+	    /* This case can't happen.  */
+	    return 0;
+	  }
+	val->encoding = ATTR_VAL_ADDRESS_INDEX;
+	val->u.uint = offset;
+	return 1;
+      }
+    case DW_FORM_ref_sup4:
+      val->encoding = ATTR_VAL_REF_SECTION;
+      val->u.uint = read_uint32 (buf);
+      return 1;
+    case DW_FORM_ref_sup8:
+      val->encoding = ATTR_VAL_REF_SECTION;
+      val->u.uint = read_uint64 (buf);
+      return 1;
+    case DW_FORM_implicit_const:
+      val->encoding = ATTR_VAL_UINT;
+      val->u.uint = implicit_val;
+      return 1;
+    case DW_FORM_loclistx:
+      /* We don't distinguish this from DW_FORM_sec_offset.  It
+       * shouldn't matter since we don't care about loclists.  */
+      val->encoding = ATTR_VAL_REF_SECTION;
+      val->u.uint = read_uleb128 (buf);
+      return 1;
+    case DW_FORM_rnglistx:
+      val->encoding = ATTR_VAL_RNGLISTS_INDEX;
+      val->u.uint = read_uleb128 (buf);
+      return 1;
+    case DW_FORM_GNU_addr_index:
+      val->encoding = ATTR_VAL_REF_SECTION;
+      val->u.uint = read_uleb128 (buf);
+      return 1;
+    case DW_FORM_GNU_str_index:
+      val->encoding = ATTR_VAL_REF_SECTION;
+      val->u.uint = read_uleb128 (buf);
+      return 1;
+    case DW_FORM_GNU_ref_alt:
+      val->u.uint = read_offset (buf, is_dwarf64);
+      if (altlink == NULL)
+	{
+	  val->encoding = ATTR_VAL_NONE;
+	  return 1;
+	}
+      val->encoding = ATTR_VAL_REF_ALT_INFO;
+      return 1;
+    case DW_FORM_strp_sup: case DW_FORM_GNU_strp_alt:
+      {
+	uint64_t offset;
+
+	offset = read_offset (buf, is_dwarf64);
+	if (altlink == NULL)
+	  {
+	    val->encoding = ATTR_VAL_NONE;
+	    return 1;
+	  }
+	if (offset >= altlink->dwarf_sections.size[DEBUG_STR])
+	  {
+	    dwarf_buf_error (buf, "DW_FORM_strp_sup out of range", 0);
+	    return 0;
+	  }
+	val->encoding = ATTR_VAL_STRING;
+	val->u.string =
+	  (const char *) altlink->dwarf_sections.data[DEBUG_STR] + offset;
+	return 1;
+      }
+    default:
+      dwarf_buf_error (buf, "unrecognized DWARF form", -1);
+      return 0;
+    }
+}
+
+/* If we can determine the value of a string attribute, set *STRING to
+   point to the string.  Return 1 on success, 0 on error.  If we don't
+   know the value, we consider that a success, and we don't change
+   *STRING.  An error is only reported for some sort of out of range
+   offset.  */
+
+static int
+resolve_string (const struct dwarf_sections *dwarf_sections, int is_dwarf64,
+		int is_bigendian, uint64_t str_offsets_base,
+		const struct attr_val *val,
+		backtrace_error_callback error_callback, void *data,
+		const char **string)
+{
+  switch (val->encoding)
+    {
+    case ATTR_VAL_STRING:
+      *string = val->u.string;
+      return 1;
+
+    case ATTR_VAL_STRING_INDEX:
+      {
+	uint64_t offset;
+	struct dwarf_buf offset_buf;
+
+	offset = val->u.uint * (is_dwarf64 ? 8 : 4) + str_offsets_base;
+	if (offset + (is_dwarf64 ? 8 : 4)
+	    > dwarf_sections->size[DEBUG_STR_OFFSETS])
+	  {
+	    error_callback (data, "DW_FORM_strx value out of range", 0);
+	    return 0;
+	  }
+
+	offset_buf.name = ".debug_str_offsets";
+	offset_buf.start = dwarf_sections->data[DEBUG_STR_OFFSETS];
+	offset_buf.buf = dwarf_sections->data[DEBUG_STR_OFFSETS] + offset;
+	offset_buf.left = dwarf_sections->size[DEBUG_STR_OFFSETS] - offset;
+	offset_buf.is_bigendian = is_bigendian;
+	offset_buf.error_callback = error_callback;
+	offset_buf.data = data;
+	offset_buf.reported_underflow = 0;
+
+	offset = read_offset (&offset_buf, is_dwarf64);
+	if (offset >= dwarf_sections->size[DEBUG_STR])
+	  {
+	    dwarf_buf_error (&offset_buf,
+			     "DW_FORM_strx offset out of range",
+			     0);
+	    return 0;
+	  }
+	*string = (const char *) dwarf_sections->data[DEBUG_STR] + offset;
+	return 1;
+      }
+
+    default:
+      return 1;
+    }
+}
+
+/* Set *ADDRESS to the real address for a ATTR_VAL_ADDRESS_INDEX.
+   Return 1 on success, 0 on error.  */
+
+static int
+resolve_addr_index (const struct dwarf_sections *dwarf_sections,
+		    uint64_t addr_base, int addrsize, int is_bigendian,
+		    uint64_t addr_index,
+		    backtrace_error_callback error_callback, void *data,
+		    uint64_t *address)
+{
+  uint64_t offset;
+  struct dwarf_buf addr_buf;
+
+  offset = addr_index * addrsize + addr_base;
+  if (offset + addrsize > dwarf_sections->size[DEBUG_ADDR])
+    {
+      error_callback (data, "DW_FORM_addrx value out of range", 0);
+      return 0;
+    }
+
+  addr_buf.name = ".debug_addr";
+  addr_buf.start = dwarf_sections->data[DEBUG_ADDR];
+  addr_buf.buf = dwarf_sections->data[DEBUG_ADDR] + offset;
+  addr_buf.left = dwarf_sections->size[DEBUG_ADDR] - offset;
+  addr_buf.is_bigendian = is_bigendian;
+  addr_buf.error_callback = error_callback;
+  addr_buf.data = data;
+  addr_buf.reported_underflow = 0;
+
+  *address = read_address (&addr_buf, addrsize);
+  return 1;
+}
+
+/* Compare a unit offset against a unit for bsearch.  */
+
+static int
+units_search (const void *vkey, const void *ventry)
+{
+  const size_t *key = (const size_t *) vkey;
+  const struct unit *entry = *((const struct unit *const *) ventry);
+  size_t offset;
+
+  offset = *key;
+  if (offset < entry->low_offset)
+    return -1;
+  else if (offset >= entry->high_offset)
+    return 1;
+  else
+    return 0;
+}
+
+/* Find a unit in PU containing OFFSET.  */
+
+static struct unit *
+find_unit (struct unit **pu, size_t units_count, size_t offset)
+{
+  struct unit **u;
+  u = bsearch (&offset, pu, units_count, sizeof (struct unit *), units_search);
+  return u == NULL ? NULL : *u;
+}
+
+/* Compare function_addrs for qsort.  When ranges are nested, make the
+   smallest one sort last.  */
+
+static int
+function_addrs_compare (const void *v1, const void *v2)
+{
+  const struct function_addrs *a1 = (const struct function_addrs *) v1;
+  const struct function_addrs *a2 = (const struct function_addrs *) v2;
+
+  if (a1->low < a2->low)
+    return -1;
+  if (a1->low > a2->low)
+    return 1;
+  if (a1->high < a2->high)
+    return 1;
+  if (a1->high > a2->high)
+    return -1;
+  return strcmp (a1->function->name, a2->function->name);
+}
+
+/* Compare a PC against a function_addrs for bsearch.  We always
+   allocate an entra entry at the end of the vector, so that this
+   routine can safely look at the next entry.  Note that if there are
+   multiple ranges containing PC, which one will be returned is
+   unpredictable.  We compensate for that in dwarf_fileline.  */
+
+static int
+function_addrs_search (const void *vkey, const void *ventry)
+{
+  const uintptr_t *key = (const uintptr_t *) vkey;
+  const struct function_addrs *entry = (const struct function_addrs *) ventry;
+  uintptr_t pc;
+
+  pc = *key;
+  if (pc < entry->low)
+    return -1;
+  else if (pc > (entry + 1)->low)
+    return 1;
+  else
+    return 0;
+}
+
+/* Add a new compilation unit address range to a vector.  This is
+   called via add_ranges.  Returns 1 on success, 0 on failure.  */
+
+static int
+add_unit_addr (struct backtrace_state *state, void *rdata,
+	       uint64_t lowpc, uint64_t highpc,
+	       backtrace_error_callback error_callback, void *data,
+	       void *pvec)
+{
+  struct unit *u = (struct unit *) rdata;
+  struct unit_addrs_vector *vec = (struct unit_addrs_vector *) pvec;
+  struct unit_addrs *p;
+
+  /* Try to merge with the last entry.  */
+  if (vec->count > 0)
+    {
+      p = (struct unit_addrs *) vec->vec.base + (vec->count - 1);
+      if ((lowpc == p->high || lowpc == p->high + 1)
+	  && u == p->u)
+	{
+	  if (highpc > p->high)
+	    p->high = highpc;
+	  return 1;
+	}
+    }
+
+  p = ((struct unit_addrs *)
+       backtrace_vector_grow (state, sizeof (struct unit_addrs),
+			      error_callback, data, &vec->vec));
+  if (p == NULL)
+    return 0;
+
+  p->low = lowpc;
+  p->high = highpc;
+  p->u = u;
+
+  ++vec->count;
+
+  return 1;
+}
+
+/* Compare unit_addrs for qsort.  When ranges are nested, make the
+   smallest one sort last.  */
+
+static int
+unit_addrs_compare (const void *v1, const void *v2)
+{
+  const struct unit_addrs *a1 = (const struct unit_addrs *) v1;
+  const struct unit_addrs *a2 = (const struct unit_addrs *) v2;
+
+  if (a1->low < a2->low)
+    return -1;
+  if (a1->low > a2->low)
+    return 1;
+  if (a1->high < a2->high)
+    return 1;
+  if (a1->high > a2->high)
+    return -1;
+  if (a1->u->lineoff < a2->u->lineoff)
+    return -1;
+  if (a1->u->lineoff > a2->u->lineoff)
+    return 1;
+  return 0;
+}
+
+/* Compare a PC against a unit_addrs for bsearch.  We always allocate
+   an entry entry at the end of the vector, so that this routine can
+   safely look at the next entry.  Note that if there are multiple
+   ranges containing PC, which one will be returned is unpredictable.
+   We compensate for that in dwarf_fileline.  */
+
+static int
+unit_addrs_search (const void *vkey, const void *ventry)
+{
+  const uintptr_t *key = (const uintptr_t *) vkey;
+  const struct unit_addrs *entry = (const struct unit_addrs *) ventry;
+  uintptr_t pc;
+
+  pc = *key;
+  if (pc < entry->low)
+    return -1;
+  else if (pc > (entry + 1)->low)
+    return 1;
+  else
+    return 0;
+}
+
+/* Sort the line vector by PC.  We want a stable sort here to maintain
+   the order of lines for the same PC values.  Since the sequence is
+   being sorted in place, their addresses cannot be relied on to
+   maintain stability.  That is the purpose of the index member.  */
+
+static int
+line_compare (const void *v1, const void *v2)
+{
+  const struct line *ln1 = (const struct line *) v1;
+  const struct line *ln2 = (const struct line *) v2;
+
+  if (ln1->pc < ln2->pc)
+    return -1;
+  else if (ln1->pc > ln2->pc)
+    return 1;
+  else if (ln1->idx < ln2->idx)
+    return -1;
+  else if (ln1->idx > ln2->idx)
+    return 1;
+  else
+    return 0;
+}
+
+/* Find a PC in a line vector.  We always allocate an extra entry at
+   the end of the lines vector, so that this routine can safely look
+   at the next entry.  Note that when there are multiple mappings for
+   the same PC value, this will return the last one.  */
+
+static int
+line_search (const void *vkey, const void *ventry)
+{
+  const uintptr_t *key = (const uintptr_t *) vkey;
+  const struct line *entry = (const struct line *) ventry;
+  uintptr_t pc;
+
+  pc = *key;
+  if (pc < entry->pc)
+    return -1;
+  else if (pc >= (entry + 1)->pc)
+    return 1;
+  else
+    return 0;
+}
+
+/* Sort the abbrevs by the abbrev code.  This function is passed to
+   both qsort and bsearch.  */
+
+static int
+abbrev_compare (const void *v1, const void *v2)
+{
+  const struct abbrev *a1 = (const struct abbrev *) v1;
+  const struct abbrev *a2 = (const struct abbrev *) v2;
+
+  if (a1->code < a2->code)
+    return -1;
+  else if (a1->code > a2->code)
+    return 1;
+  else
+    {
+      /* This really shouldn't happen.  It means there are two
+	 different abbrevs with the same code, and that means we don't
+	 know which one lookup_abbrev should return.  */
+      return 0;
+    }
+}
+
+/* Read the abbreviation table for a compilation unit.  Returns 1 on
+   success, 0 on failure.  */
+
+static int
+read_abbrevs (struct backtrace_state *state, uint64_t abbrev_offset,
+	      const unsigned char *dwarf_abbrev, size_t dwarf_abbrev_size,
+	      int is_bigendian, backtrace_error_callback error_callback,
+	      void *data, struct abbrevs *abbrevs)
+{
+  struct dwarf_buf abbrev_buf;
+  struct dwarf_buf count_buf;
+  size_t num_abbrevs;
+
+  abbrevs->num_abbrevs = 0;
+  abbrevs->abbrevs = NULL;
+
+  if (abbrev_offset >= dwarf_abbrev_size)
+    {
+      error_callback (data, "abbrev offset out of range", 0);
+      return 0;
+    }
+
+  abbrev_buf.name = ".debug_abbrev";
+  abbrev_buf.start = dwarf_abbrev;
+  abbrev_buf.buf = dwarf_abbrev + abbrev_offset;
+  abbrev_buf.left = dwarf_abbrev_size - abbrev_offset;
+  abbrev_buf.is_bigendian = is_bigendian;
+  abbrev_buf.error_callback = error_callback;
+  abbrev_buf.data = data;
+  abbrev_buf.reported_underflow = 0;
+
+  /* Count the number of abbrevs in this list.  */
+
+  count_buf = abbrev_buf;
+  num_abbrevs = 0;
+  while (read_uleb128 (&count_buf) != 0)
+    {
+      if (count_buf.reported_underflow)
+	return 0;
+      ++num_abbrevs;
+      // Skip tag.
+      read_uleb128 (&count_buf);
+      // Skip has_children.
+      read_byte (&count_buf);
+      // Skip attributes.
+      while (read_uleb128 (&count_buf) != 0)
+	{
+	  uint64_t form;
+
+	  form = read_uleb128 (&count_buf);
+	  if ((enum dwarf_form) form == DW_FORM_implicit_const)
+	    read_sleb128 (&count_buf);
+	}
+      // Skip form of last attribute.
+      read_uleb128 (&count_buf);
+    }
+
+  if (count_buf.reported_underflow)
+    return 0;
+
+  if (num_abbrevs == 0)
+    return 1;
+
+  abbrevs->abbrevs = ((struct abbrev *)
+		      backtrace_alloc (state,
+				       num_abbrevs * sizeof (struct abbrev),
+				       error_callback, data));
+  if (abbrevs->abbrevs == NULL)
+    return 0;
+  abbrevs->num_abbrevs = num_abbrevs;
+  memset (abbrevs->abbrevs, 0, num_abbrevs * sizeof (struct abbrev));
+
+  num_abbrevs = 0;
+  while (1)
+    {
+      uint64_t code;
+      struct abbrev a;
+      size_t num_attrs;
+      struct attr *attrs;
+
+      if (abbrev_buf.reported_underflow)
+	goto fail;
+
+      code = read_uleb128 (&abbrev_buf);
+      if (code == 0)
+	break;
+
+      a.code = code;
+      a.tag = (enum dwarf_tag) read_uleb128 (&abbrev_buf);
+      a.has_children = read_byte (&abbrev_buf);
+
+      count_buf = abbrev_buf;
+      num_attrs = 0;
+      while (read_uleb128 (&count_buf) != 0)
+	{
+	  uint64_t form;
+
+	  ++num_attrs;
+	  form = read_uleb128 (&count_buf);
+	  if ((enum dwarf_form) form == DW_FORM_implicit_const)
+	    read_sleb128 (&count_buf);
+	}
+
+      if (num_attrs == 0)
+	{
+	  attrs = NULL;
+	  read_uleb128 (&abbrev_buf);
+	  read_uleb128 (&abbrev_buf);
+	}
+      else
+	{
+	  attrs = ((struct attr *)
+		   backtrace_alloc (state, num_attrs * sizeof *attrs,
+				    error_callback, data));
+	  if (attrs == NULL)
+	    goto fail;
+	  num_attrs = 0;
+	  while (1)
+	    {
+	      uint64_t name;
+	      uint64_t form;
+
+	      name = read_uleb128 (&abbrev_buf);
+	      form = read_uleb128 (&abbrev_buf);
+	      if (name == 0)
+		break;
+	      attrs[num_attrs].name = (enum dwarf_attribute) name;
+	      attrs[num_attrs].form = (enum dwarf_form) form;
+	      if ((enum dwarf_form) form == DW_FORM_implicit_const)
+		attrs[num_attrs].val = read_sleb128 (&abbrev_buf);
+	      else
+		attrs[num_attrs].val = 0;
+	      ++num_attrs;
+	    }
+	}
+
+      a.num_attrs = num_attrs;
+      a.attrs = attrs;
+
+      abbrevs->abbrevs[num_abbrevs] = a;
+      ++num_abbrevs;
+    }
+
+  backtrace_qsort (abbrevs->abbrevs, abbrevs->num_abbrevs,
+		   sizeof (struct abbrev), abbrev_compare);
+
+  return 1;
+
+ fail:
+  free_abbrevs (state, abbrevs, error_callback, data);
+  return 0;
+}
+
+/* Return the abbrev information for an abbrev code.  */
+
+static const struct abbrev *
+lookup_abbrev (struct abbrevs *abbrevs, uint64_t code,
+	       backtrace_error_callback error_callback, void *data)
+{
+  struct abbrev key;
+  void *p;
+
+  /* With GCC, where abbrevs are simply numbered in order, we should
+     be able to just look up the entry.  */
+  if (code - 1 < abbrevs->num_abbrevs
+      && abbrevs->abbrevs[code - 1].code == code)
+    return &abbrevs->abbrevs[code - 1];
+
+  /* Otherwise we have to search.  */
+  memset (&key, 0, sizeof key);
+  key.code = code;
+  p = bsearch (&key, abbrevs->abbrevs, abbrevs->num_abbrevs,
+	       sizeof (struct abbrev), abbrev_compare);
+  if (p == NULL)
+    {
+      error_callback (data, "invalid abbreviation code", 0);
+      return NULL;
+    }
+  return (const struct abbrev *) p;
+}
+
+/* This struct is used to gather address range information while
+   reading attributes.  We use this while building a mapping from
+   address ranges to compilation units and then again while mapping
+   from address ranges to function entries.  Normally either
+   lowpc/highpc is set or ranges is set.  */
+
+struct pcrange {
+  uint64_t lowpc;		/* The low PC value.  */
+  int have_lowpc;		/* Whether a low PC value was found.  */
+  int lowpc_is_addr_index;	/* Whether lowpc is in .debug_addr.  */
+  uint64_t highpc;		/* The high PC value.  */
+  int have_highpc;		/* Whether a high PC value was found.  */
+  int highpc_is_relative;	/* Whether highpc is relative to lowpc.  */
+  int highpc_is_addr_index;	/* Whether highpc is in .debug_addr.  */
+  uint64_t ranges;		/* Offset in ranges section.  */
+  int have_ranges;		/* Whether ranges is valid.  */
+  int ranges_is_index;		/* Whether ranges is DW_FORM_rnglistx.  */
+};
+
+/* Update PCRANGE from an attribute value.  */
+
+static void
+update_pcrange (const struct attr* attr, const struct attr_val* val,
+		struct pcrange *pcrange)
+{
+  switch (attr->name)
+    {
+    case DW_AT_low_pc:
+      if (val->encoding == ATTR_VAL_ADDRESS)
+	{
+	  pcrange->lowpc = val->u.uint;
+	  pcrange->have_lowpc = 1;
+	}
+      else if (val->encoding == ATTR_VAL_ADDRESS_INDEX)
+	{
+	  pcrange->lowpc = val->u.uint;
+	  pcrange->have_lowpc = 1;
+	  pcrange->lowpc_is_addr_index = 1;
+	}
+      break;
+
+    case DW_AT_high_pc:
+      if (val->encoding == ATTR_VAL_ADDRESS)
+	{
+	  pcrange->highpc = val->u.uint;
+	  pcrange->have_highpc = 1;
+	}
+      else if (val->encoding == ATTR_VAL_UINT)
+	{
+	  pcrange->highpc = val->u.uint;
+	  pcrange->have_highpc = 1;
+	  pcrange->highpc_is_relative = 1;
+	}
+      else if (val->encoding == ATTR_VAL_ADDRESS_INDEX)
+	{
+	  pcrange->highpc = val->u.uint;
+	  pcrange->have_highpc = 1;
+	  pcrange->highpc_is_addr_index = 1;
+	}
+      break;
+
+    case DW_AT_ranges:
+      if (val->encoding == ATTR_VAL_UINT
+	  || val->encoding == ATTR_VAL_REF_SECTION)
+	{
+	  pcrange->ranges = val->u.uint;
+	  pcrange->have_ranges = 1;
+	}
+      else if (val->encoding == ATTR_VAL_RNGLISTS_INDEX)
+	{
+	  pcrange->ranges = val->u.uint;
+	  pcrange->have_ranges = 1;
+	  pcrange->ranges_is_index = 1;
+	}
+      break;
+
+    default:
+      break;
+    }
+}
+
+/* Call ADD_RANGE for a low/high PC pair.  Returns 1 on success, 0 on
+  error.  */
+
+static int
+add_low_high_range (struct backtrace_state *state,
+		    const struct dwarf_sections *dwarf_sections,
+		    uintptr_t base_address, int is_bigendian,
+		    struct unit *u, const struct pcrange *pcrange,
+		    int (*add_range) (struct backtrace_state *state,
+				      void *rdata, uint64_t lowpc,
+				      uint64_t highpc,
+				      backtrace_error_callback error_callback,
+				      void *data, void *vec),
+		    void *rdata,
+		    backtrace_error_callback error_callback, void *data,
+		    void *vec)
+{
+  uint64_t lowpc;
+  uint64_t highpc;
+
+  lowpc = pcrange->lowpc;
+  if (pcrange->lowpc_is_addr_index)
+    {
+      if (!resolve_addr_index (dwarf_sections, u->addr_base, u->addrsize,
+			       is_bigendian, lowpc, error_callback, data,
+			       &lowpc))
+	return 0;
+    }
+
+  highpc = pcrange->highpc;
+  if (pcrange->highpc_is_addr_index)
+    {
+      if (!resolve_addr_index (dwarf_sections, u->addr_base, u->addrsize,
+			       is_bigendian, highpc, error_callback, data,
+			       &highpc))
+	return 0;
+    }
+  if (pcrange->highpc_is_relative)
+    highpc += lowpc;
+
+  /* Add in the base address of the module when recording PC values,
+     so that we can look up the PC directly.  */
+  lowpc += base_address;
+  highpc += base_address;
+
+  return add_range (state, rdata, lowpc, highpc, error_callback, data, vec);
+}
+
+/* Call ADD_RANGE for each range read from .debug_ranges, as used in
+   DWARF versions 2 through 4.  */
+
+static int
+add_ranges_from_ranges (
+    struct backtrace_state *state,
+    const struct dwarf_sections *dwarf_sections,
+    uintptr_t base_address, int is_bigendian,
+    struct unit *u, uint64_t base,
+    const struct pcrange *pcrange,
+    int (*add_range) (struct backtrace_state *state, void *rdata,
+		      uint64_t lowpc, uint64_t highpc,
+		      backtrace_error_callback error_callback, void *data,
+		      void *vec),
+    void *rdata,
+    backtrace_error_callback error_callback, void *data,
+    void *vec)
+{
+  struct dwarf_buf ranges_buf;
+
+  if (pcrange->ranges >= dwarf_sections->size[DEBUG_RANGES])
+    {
+      error_callback (data, "ranges offset out of range", 0);
+      return 0;
+    }
+
+  ranges_buf.name = ".debug_ranges";
+  ranges_buf.start = dwarf_sections->data[DEBUG_RANGES];
+  ranges_buf.buf = dwarf_sections->data[DEBUG_RANGES] + pcrange->ranges;
+  ranges_buf.left = dwarf_sections->size[DEBUG_RANGES] - pcrange->ranges;
+  ranges_buf.is_bigendian = is_bigendian;
+  ranges_buf.error_callback = error_callback;
+  ranges_buf.data = data;
+  ranges_buf.reported_underflow = 0;
+
+  while (1)
+    {
+      uint64_t low;
+      uint64_t high;
+
+      if (ranges_buf.reported_underflow)
+	return 0;
+
+      low = read_address (&ranges_buf, u->addrsize);
+      high = read_address (&ranges_buf, u->addrsize);
+
+      if (low == 0 && high == 0)
+	break;
+
+      if (is_highest_address (low, u->addrsize))
+	base = high;
+      else
+	{
+	  if (!add_range (state, rdata, 
+			  low + base + base_address,
+			  high + base + base_address,
+			  error_callback, data, vec))
+	    return 0;
+	}
+    }
+
+  if (ranges_buf.reported_underflow)
+    return 0;
+
+  return 1;
+}
+
+/* Call ADD_RANGE for each range read from .debug_rnglists, as used in
+   DWARF version 5.  */
+
+static int
+add_ranges_from_rnglists (
+    struct backtrace_state *state,
+    const struct dwarf_sections *dwarf_sections,
+    uintptr_t base_address, int is_bigendian,
+    struct unit *u, uint64_t base,
+    const struct pcrange *pcrange,
+    int (*add_range) (struct backtrace_state *state, void *rdata,
+		      uint64_t lowpc, uint64_t highpc,
+		      backtrace_error_callback error_callback, void *data,
+		      void *vec),
+    void *rdata,
+    backtrace_error_callback error_callback, void *data,
+    void *vec)
+{
+  uint64_t offset;
+  struct dwarf_buf rnglists_buf;
+
+  if (!pcrange->ranges_is_index)
+    offset = pcrange->ranges;
+  else
+    offset = u->rnglists_base + pcrange->ranges * (u->is_dwarf64 ? 8 : 4);
+  if (offset >= dwarf_sections->size[DEBUG_RNGLISTS])
+    {
+      error_callback (data, "rnglists offset out of range", 0);
+      return 0;
+    }
+
+  rnglists_buf.name = ".debug_rnglists";
+  rnglists_buf.start = dwarf_sections->data[DEBUG_RNGLISTS];
+  rnglists_buf.buf = dwarf_sections->data[DEBUG_RNGLISTS] + offset;
+  rnglists_buf.left = dwarf_sections->size[DEBUG_RNGLISTS] - offset;
+  rnglists_buf.is_bigendian = is_bigendian;
+  rnglists_buf.error_callback = error_callback;
+  rnglists_buf.data = data;
+  rnglists_buf.reported_underflow = 0;
+
+  if (pcrange->ranges_is_index)
+    {
+      offset = read_offset (&rnglists_buf, u->is_dwarf64);
+      offset += u->rnglists_base;
+      if (offset >= dwarf_sections->size[DEBUG_RNGLISTS])
+	{
+	  error_callback (data, "rnglists index offset out of range", 0);
+	  return 0;
+	}
+      rnglists_buf.buf = dwarf_sections->data[DEBUG_RNGLISTS] + offset;
+      rnglists_buf.left = dwarf_sections->size[DEBUG_RNGLISTS] - offset;
+    }
+
+  while (1)
+    {
+      unsigned char rle;
+
+      rle = read_byte (&rnglists_buf);
+      if (rle == DW_RLE_end_of_list)
+	break;
+      switch (rle)
+	{
+	case DW_RLE_base_addressx:
+	  {
+	    uint64_t index;
+
+	    index = read_uleb128 (&rnglists_buf);
+	    if (!resolve_addr_index (dwarf_sections, u->addr_base,
+				     u->addrsize, is_bigendian, index,
+				     error_callback, data, &base))
+	      return 0;
+	  }
+	  break;
+
+	case DW_RLE_startx_endx:
+	  {
+	    uint64_t index;
+	    uint64_t low;
+	    uint64_t high;
+
+	    index = read_uleb128 (&rnglists_buf);
+	    if (!resolve_addr_index (dwarf_sections, u->addr_base,
+				     u->addrsize, is_bigendian, index,
+				     error_callback, data, &low))
+	      return 0;
+	    index = read_uleb128 (&rnglists_buf);
+	    if (!resolve_addr_index (dwarf_sections, u->addr_base,
+				     u->addrsize, is_bigendian, index,
+				     error_callback, data, &high))
+	      return 0;
+	    if (!add_range (state, rdata, low + base_address,
+			    high + base_address, error_callback, data,
+			    vec))
+	      return 0;
+	  }
+	  break;
+
+	case DW_RLE_startx_length:
+	  {
+	    uint64_t index;
+	    uint64_t low;
+	    uint64_t length;
+
+	    index = read_uleb128 (&rnglists_buf);
+	    if (!resolve_addr_index (dwarf_sections, u->addr_base,
+				     u->addrsize, is_bigendian, index,
+				     error_callback, data, &low))
+	      return 0;
+	    length = read_uleb128 (&rnglists_buf);
+	    low += base_address;
+	    if (!add_range (state, rdata, low, low + length,
+			    error_callback, data, vec))
+	      return 0;
+	  }
+	  break;
+
+	case DW_RLE_offset_pair:
+	  {
+	    uint64_t low;
+	    uint64_t high;
+
+	    low = read_uleb128 (&rnglists_buf);
+	    high = read_uleb128 (&rnglists_buf);
+	    if (!add_range (state, rdata, low + base + base_address,
+			    high + base + base_address,
+			    error_callback, data, vec))
+	      return 0;
+	  }
+	  break;
+
+	case DW_RLE_base_address:
+	  base = read_address (&rnglists_buf, u->addrsize);
+	  break;
+
+	case DW_RLE_start_end:
+	  {
+	    uint64_t low;
+	    uint64_t high;
+
+	    low = read_address (&rnglists_buf, u->addrsize);
+	    high = read_address (&rnglists_buf, u->addrsize);
+	    if (!add_range (state, rdata, low + base_address,
+			    high + base_address, error_callback, data,
+			    vec))
+	      return 0;
+	  }
+	  break;
+
+	case DW_RLE_start_length:
+	  {
+	    uint64_t low;
+	    uint64_t length;
+
+	    low = read_address (&rnglists_buf, u->addrsize);
+	    length = read_uleb128 (&rnglists_buf);
+	    low += base_address;
+	    if (!add_range (state, rdata, low, low + length,
+			    error_callback, data, vec))
+	      return 0;
+	  }
+	  break;
+
+	default:
+	  dwarf_buf_error (&rnglists_buf, "unrecognized DW_RLE value", -1);
+	  return 0;
+	}
+    }
+
+  if (rnglists_buf.reported_underflow)
+    return 0;
+
+  return 1;
+}
+
+/* Call ADD_RANGE for each lowpc/highpc pair in PCRANGE.  RDATA is
+   passed to ADD_RANGE, and is either a struct unit * or a struct
+   function *.  VEC is the vector we are adding ranges to, and is
+   either a struct unit_addrs_vector * or a struct function_vector *.
+   Returns 1 on success, 0 on error.  */
+
+static int
+add_ranges (struct backtrace_state *state,
+	    const struct dwarf_sections *dwarf_sections,
+	    uintptr_t base_address, int is_bigendian,
+	    struct unit *u, uint64_t base, const struct pcrange *pcrange,
+	    int (*add_range) (struct backtrace_state *state, void *rdata, 
+			      uint64_t lowpc, uint64_t highpc,
+			      backtrace_error_callback error_callback,
+			      void *data, void *vec),
+	    void *rdata,
+	    backtrace_error_callback error_callback, void *data,
+	    void *vec)
+{
+  if (pcrange->have_lowpc && pcrange->have_highpc)
+    return add_low_high_range (state, dwarf_sections, base_address,
+			       is_bigendian, u, pcrange, add_range, rdata,
+			       error_callback, data, vec);
+
+  if (!pcrange->have_ranges)
+    {
+      /* Did not find any address ranges to add.  */
+      return 1;
+    }
+
+  if (u->version < 5)
+    return add_ranges_from_ranges (state, dwarf_sections, base_address,
+				   is_bigendian, u, base, pcrange, add_range,
+				   rdata, error_callback, data, vec);
+  else
+    return add_ranges_from_rnglists (state, dwarf_sections, base_address,
+				     is_bigendian, u, base, pcrange, add_range,
+				     rdata, error_callback, data, vec);
+}
+
+/* Find the address range covered by a compilation unit, reading from
+   UNIT_BUF and adding values to U.  Returns 1 if all data could be
+   read, 0 if there is some error.  */
+
+static int
+find_address_ranges (struct backtrace_state *state, uintptr_t base_address,
+		     struct dwarf_buf *unit_buf,
+		     const struct dwarf_sections *dwarf_sections,
+		     int is_bigendian, struct dwarf_data *altlink,
+		     backtrace_error_callback error_callback, void *data,
+		     struct unit *u, struct unit_addrs_vector *addrs,
+		     enum dwarf_tag *unit_tag)
+{
+  while (unit_buf->left > 0)
+    {
+      uint64_t code;
+      const struct abbrev *abbrev;
+      struct pcrange pcrange;
+      struct attr_val name_val;
+      int have_name_val;
+      struct attr_val comp_dir_val;
+      int have_comp_dir_val;
+      size_t i;
+
+      code = read_uleb128 (unit_buf);
+      if (code == 0)
+	return 1;
+
+      abbrev = lookup_abbrev (&u->abbrevs, code, error_callback, data);
+      if (abbrev == NULL)
+	return 0;
+
+      if (unit_tag != NULL)
+	*unit_tag = abbrev->tag;
+
+      memset (&pcrange, 0, sizeof pcrange);
+      memset (&name_val, 0, sizeof name_val);
+      have_name_val = 0;
+      memset (&comp_dir_val, 0, sizeof comp_dir_val);
+      have_comp_dir_val = 0;
+      for (i = 0; i < abbrev->num_attrs; ++i)
+	{
+	  struct attr_val val;
+
+	  if (!read_attribute (abbrev->attrs[i].form, abbrev->attrs[i].val,
+			       unit_buf, u->is_dwarf64, u->version,
+			       u->addrsize, dwarf_sections, altlink, &val))
+	    return 0;
+
+	  switch (abbrev->attrs[i].name)
+	    {
+	    case DW_AT_low_pc: case DW_AT_high_pc: case DW_AT_ranges:
+	      update_pcrange (&abbrev->attrs[i], &val, &pcrange);
+	      break;
+
+	    case DW_AT_stmt_list:
+	      if ((abbrev->tag == DW_TAG_compile_unit
+		   || abbrev->tag == DW_TAG_skeleton_unit)
+		  && (val.encoding == ATTR_VAL_UINT
+		      || val.encoding == ATTR_VAL_REF_SECTION))
+		u->lineoff = val.u.uint;
+	      break;
+
+	    case DW_AT_name:
+	      if (abbrev->tag == DW_TAG_compile_unit
+		  || abbrev->tag == DW_TAG_skeleton_unit)
+		{
+		  name_val = val;
+		  have_name_val = 1;
+		}
+	      break;
+
+	    case DW_AT_comp_dir:
+	      if (abbrev->tag == DW_TAG_compile_unit
+		  || abbrev->tag == DW_TAG_skeleton_unit)
+		{
+		  comp_dir_val = val;
+		  have_comp_dir_val = 1;
+		}
+	      break;
+
+	    case DW_AT_str_offsets_base:
+	      if ((abbrev->tag == DW_TAG_compile_unit
+		   || abbrev->tag == DW_TAG_skeleton_unit)
+		  && val.encoding == ATTR_VAL_REF_SECTION)
+		u->str_offsets_base = val.u.uint;
+	      break;
+
+	    case DW_AT_addr_base:
+	      if ((abbrev->tag == DW_TAG_compile_unit
+		   || abbrev->tag == DW_TAG_skeleton_unit)
+		  && val.encoding == ATTR_VAL_REF_SECTION)
+		u->addr_base = val.u.uint;
+	      break;
+
+	    case DW_AT_rnglists_base:
+	      if ((abbrev->tag == DW_TAG_compile_unit
+		   || abbrev->tag == DW_TAG_skeleton_unit)
+		  && val.encoding == ATTR_VAL_REF_SECTION)
+		u->rnglists_base = val.u.uint;
+	      break;
+
+	    default:
+	      break;
+	    }
+	}
+
+      // Resolve strings after we're sure that we have seen
+      // DW_AT_str_offsets_base.
+      if (have_name_val)
+	{
+	  if (!resolve_string (dwarf_sections, u->is_dwarf64, is_bigendian,
+			       u->str_offsets_base, &name_val,
+			       error_callback, data, &u->filename))
+	    return 0;
+	}
+      if (have_comp_dir_val)
+	{
+	  if (!resolve_string (dwarf_sections, u->is_dwarf64, is_bigendian,
+			       u->str_offsets_base, &comp_dir_val,
+			       error_callback, data, &u->comp_dir))
+	    return 0;
+	}
+
+      if (abbrev->tag == DW_TAG_compile_unit
+	  || abbrev->tag == DW_TAG_subprogram
+	  || abbrev->tag == DW_TAG_skeleton_unit)
+	{
+	  if (!add_ranges (state, dwarf_sections, base_address,
+			   is_bigendian, u, pcrange.lowpc, &pcrange,
+			   add_unit_addr, (void *) u, error_callback, data,
+			   (void *) addrs))
+	    return 0;
+
+	  /* If we found the PC range in the DW_TAG_compile_unit or
+	     DW_TAG_skeleton_unit, we can stop now.  */
+	  if ((abbrev->tag == DW_TAG_compile_unit
+	       || abbrev->tag == DW_TAG_skeleton_unit)
+	      && (pcrange.have_ranges
+		  || (pcrange.have_lowpc && pcrange.have_highpc)))
+	    return 1;
+	}
+
+      if (abbrev->has_children)
+	{
+	  if (!find_address_ranges (state, base_address, unit_buf,
+				    dwarf_sections, is_bigendian, altlink,
+				    error_callback, data, u, addrs, NULL))
+	    return 0;
+	}
+    }
+
+  return 1;
+}
+
+/* Build a mapping from address ranges to the compilation units where
+   the line number information for that range can be found.  Returns 1
+   on success, 0 on failure.  */
+
+static int
+build_address_map (struct backtrace_state *state, uintptr_t base_address,
+		   const struct dwarf_sections *dwarf_sections,
+		   int is_bigendian, struct dwarf_data *altlink,
+		   backtrace_error_callback error_callback, void *data,
+		   struct unit_addrs_vector *addrs,
+		   struct unit_vector *unit_vec)
+{
+  struct dwarf_buf info;
+  struct backtrace_vector units;
+  size_t units_count;
+  size_t i;
+  struct unit **pu;
+  size_t unit_offset = 0;
+  struct unit_addrs *pa;
+
+  memset (&addrs->vec, 0, sizeof addrs->vec);
+  memset (&unit_vec->vec, 0, sizeof unit_vec->vec);
+  addrs->count = 0;
+  unit_vec->count = 0;
+
+  /* Read through the .debug_info section.  FIXME: Should we use the
+     .debug_aranges section?  gdb and addr2line don't use it, but I'm
+     not sure why.  */
+
+  info.name = ".debug_info";
+  info.start = dwarf_sections->data[DEBUG_INFO];
+  info.buf = info.start;
+  info.left = dwarf_sections->size[DEBUG_INFO];
+  info.is_bigendian = is_bigendian;
+  info.error_callback = error_callback;
+  info.data = data;
+  info.reported_underflow = 0;
+
+  memset (&units, 0, sizeof units);
+  units_count = 0;
+
+  while (info.left > 0)
+    {
+      const unsigned char *unit_data_start;
+      uint64_t len;
+      int is_dwarf64;
+      struct dwarf_buf unit_buf;
+      int version;
+      int unit_type;
+      uint64_t abbrev_offset;
+      int addrsize;
+      struct unit *u;
+      enum dwarf_tag unit_tag;
+
+      if (info.reported_underflow)
+	goto fail;
+
+      unit_data_start = info.buf;
+
+      len = read_initial_length (&info, &is_dwarf64);
+      unit_buf = info;
+      unit_buf.left = len;
+
+      if (!advance (&info, len))
+	goto fail;
+
+      version = read_uint16 (&unit_buf);
+      if (version < 2 || version > 5)
+	{
+	  dwarf_buf_error (&unit_buf, "unrecognized DWARF version", -1);
+	  goto fail;
+	}
+
+      if (version < 5)
+	unit_type = 0;
+      else
+	{
+	  unit_type = read_byte (&unit_buf);
+	  if (unit_type == DW_UT_type || unit_type == DW_UT_split_type)
+	    {
+	      /* This unit doesn't have anything we need.  */
+	      continue;
+	    }
+	}
+
+      pu = ((struct unit **)
+	    backtrace_vector_grow (state, sizeof (struct unit *),
+				   error_callback, data, &units));
+      if (pu == NULL)
+	  goto fail;
+
+      u = ((struct unit *)
+	   backtrace_alloc (state, sizeof *u, error_callback, data));
+      if (u == NULL)
+	goto fail;
+
+      *pu = u;
+      ++units_count;
+
+      if (version < 5)
+	addrsize = 0; /* Set below.  */
+      else
+	addrsize = read_byte (&unit_buf);
+
+      memset (&u->abbrevs, 0, sizeof u->abbrevs);
+      abbrev_offset = read_offset (&unit_buf, is_dwarf64);
+      if (!read_abbrevs (state, abbrev_offset,
+			 dwarf_sections->data[DEBUG_ABBREV],
+			 dwarf_sections->size[DEBUG_ABBREV],
+			 is_bigendian, error_callback, data, &u->abbrevs))
+	goto fail;
+
+      if (version < 5)
+	addrsize = read_byte (&unit_buf);
+
+      switch (unit_type)
+	{
+	case 0:
+	  break;
+	case DW_UT_compile: case DW_UT_partial:
+	  break;
+	case DW_UT_skeleton: case DW_UT_split_compile:
+	  read_uint64 (&unit_buf); /* dwo_id */
+	  break;
+	default:
+	  break;
+	}
+
+      u->low_offset = unit_offset;
+      unit_offset += len + (is_dwarf64 ? 12 : 4);
+      u->high_offset = unit_offset;
+      u->unit_data = unit_buf.buf;
+      u->unit_data_len = unit_buf.left;
+      u->unit_data_offset = unit_buf.buf - unit_data_start;
+      u->version = version;
+      u->is_dwarf64 = is_dwarf64;
+      u->addrsize = addrsize;
+      u->filename = NULL;
+      u->comp_dir = NULL;
+      u->abs_filename = NULL;
+      u->lineoff = 0;
+      u->str_offsets_base = 0;
+      u->addr_base = 0;
+      u->rnglists_base = 0;
+
+      /* The actual line number mappings will be read as needed.  */
+      u->lines = NULL;
+      u->lines_count = 0;
+      u->function_addrs = NULL;
+      u->function_addrs_count = 0;
+
+      if (!find_address_ranges (state, base_address, &unit_buf, dwarf_sections,
+				is_bigendian, altlink, error_callback, data,
+				u, addrs, &unit_tag))
+	goto fail;
+
+      if (unit_buf.reported_underflow)
+	goto fail;
+    }
+  if (info.reported_underflow)
+    goto fail;
+
+  /* Add a trailing addrs entry, but don't include it in addrs->count.  */
+  pa = ((struct unit_addrs *)
+	backtrace_vector_grow (state, sizeof (struct unit_addrs),
+			       error_callback, data, &addrs->vec));
+  if (pa == NULL)
+    goto fail;
+  pa->low = 0;
+  --pa->low;
+  pa->high = pa->low;
+  pa->u = NULL;
+
+  unit_vec->vec = units;
+  unit_vec->count = units_count;
+  return 1;
+
+ fail:
+  if (units_count > 0)
+    {
+      pu = (struct unit **) units.base;
+      for (i = 0; i < units_count; i++)
+	{
+	  free_abbrevs (state, &pu[i]->abbrevs, error_callback, data);
+	  backtrace_free (state, pu[i], sizeof **pu, error_callback, data);
+	}
+      backtrace_vector_free (state, &units, error_callback, data);
+    }
+  if (addrs->count > 0)
+    {
+      backtrace_vector_free (state, &addrs->vec, error_callback, data);
+      addrs->count = 0;
+    }
+  return 0;
+}
+
+/* Add a new mapping to the vector of line mappings that we are
+   building.  Returns 1 on success, 0 on failure.  */
+
+static int
+add_line (struct backtrace_state *state, struct dwarf_data *ddata,
+	  uintptr_t pc, const char *filename, int lineno,
+	  backtrace_error_callback error_callback, void *data,
+	  struct line_vector *vec)
+{
+  struct line *ln;
+
+  /* If we are adding the same mapping, ignore it.  This can happen
+     when using discriminators.  */
+  if (vec->count > 0)
+    {
+      ln = (struct line *) vec->vec.base + (vec->count - 1);
+      if (pc == ln->pc && filename == ln->filename && lineno == ln->lineno)
+	return 1;
+    }
+
+  ln = ((struct line *)
+	backtrace_vector_grow (state, sizeof (struct line), error_callback,
+			       data, &vec->vec));
+  if (ln == NULL)
+    return 0;
+
+  /* Add in the base address here, so that we can look up the PC
+     directly.  */
+  ln->pc = pc + ddata->base_address;
+
+  ln->filename = filename;
+  ln->lineno = lineno;
+  ln->idx = vec->count;
+
+  ++vec->count;
+
+  return 1;
+}
+
+/* Free the line header information.  */
+
+static void
+free_line_header (struct backtrace_state *state, struct line_header *hdr,
+		  backtrace_error_callback error_callback, void *data)
+{
+  if (hdr->dirs_count != 0)
+    backtrace_free (state, hdr->dirs, hdr->dirs_count * sizeof (const char *),
+		    error_callback, data);
+  backtrace_free (state, hdr->filenames,
+		  hdr->filenames_count * sizeof (char *),
+		  error_callback, data);
+}
+
+/* Read the directories and file names for a line header for version
+   2, setting fields in HDR.  Return 1 on success, 0 on failure.  */
+
+static int
+read_v2_paths (struct backtrace_state *state, struct unit *u,
+	       struct dwarf_buf *hdr_buf, struct line_header *hdr)
+{
+  const unsigned char *p;
+  const unsigned char *pend;
+  size_t i;
+
+  /* Count the number of directory entries.  */
+  hdr->dirs_count = 0;
+  p = hdr_buf->buf;
+  pend = p + hdr_buf->left;
+  while (p < pend && *p != '\0')
+    {
+      p += strnlen((const char *) p, pend - p) + 1;
+      ++hdr->dirs_count;
+    }
+
+  /* The index of the first entry in the list of directories is 1.  Index 0 is
+     used for the current directory of the compilation.  To simplify index
+     handling, we set entry 0 to the compilation unit directory.  */
+  ++hdr->dirs_count;
+  hdr->dirs = ((const char **)
+	       backtrace_alloc (state,
+				hdr->dirs_count * sizeof (const char *),
+				hdr_buf->error_callback,
+				hdr_buf->data));
+  if (hdr->dirs == NULL)
+    return 0;
+
+  hdr->dirs[0] = u->comp_dir;
+  i = 1;
+  while (*hdr_buf->buf != '\0')
+    {
+      if (hdr_buf->reported_underflow)
+	return 0;
+
+      hdr->dirs[i] = read_string (hdr_buf);
+      if (hdr->dirs[i] == NULL)
+	return 0;
+      ++i;
+    }
+  if (!advance (hdr_buf, 1))
+    return 0;
+
+  /* Count the number of file entries.  */
+  hdr->filenames_count = 0;
+  p = hdr_buf->buf;
+  pend = p + hdr_buf->left;
+  while (p < pend && *p != '\0')
+    {
+      p += strnlen ((const char *) p, pend - p) + 1;
+      p += leb128_len (p);
+      p += leb128_len (p);
+      p += leb128_len (p);
+      ++hdr->filenames_count;
+    }
+
+  /* The index of the first entry in the list of file names is 1.  Index 0 is
+     used for the DW_AT_name of the compilation unit.  To simplify index
+     handling, we set entry 0 to the compilation unit file name.  */
+  ++hdr->filenames_count;
+  hdr->filenames = ((const char **)
+		    backtrace_alloc (state,
+				     hdr->filenames_count * sizeof (char *),
+				     hdr_buf->error_callback,
+				     hdr_buf->data));
+  if (hdr->filenames == NULL)
+    return 0;
+  hdr->filenames[0] = u->filename;
+  i = 1;
+  while (*hdr_buf->buf != '\0')
+    {
+      const char *filename;
+      uint64_t dir_index;
+
+      if (hdr_buf->reported_underflow)
+	return 0;
+
+      filename = read_string (hdr_buf);
+      if (filename == NULL)
+	return 0;
+      dir_index = read_uleb128 (hdr_buf);
+      if (IS_ABSOLUTE_PATH (filename)
+	  || (dir_index < hdr->dirs_count && hdr->dirs[dir_index] == NULL))
+	hdr->filenames[i] = filename;
+      else
+	{
+	  const char *dir;
+	  size_t dir_len;
+	  size_t filename_len;
+	  char *s;
+
+	  if (dir_index < hdr->dirs_count)
+	    dir = hdr->dirs[dir_index];
+	  else
+	    {
+	      dwarf_buf_error (hdr_buf,
+			       ("invalid directory index in "
+				"line number program header"),
+			       0);
+	      return 0;
+	    }
+	  dir_len = strlen (dir);
+	  filename_len = strlen (filename);
+	  s = ((char *) backtrace_alloc (state, dir_len + filename_len + 2,
+					 hdr_buf->error_callback,
+					 hdr_buf->data));
+	  if (s == NULL)
+	    return 0;
+	  memcpy (s, dir, dir_len);
+	  /* FIXME: If we are on a DOS-based file system, and the
+	     directory or the file name use backslashes, then we
+	     should use a backslash here.  */
+	  s[dir_len] = '/';
+	  memcpy (s + dir_len + 1, filename, filename_len + 1);
+	  hdr->filenames[i] = s;
+	}
+
+      /* Ignore the modification time and size.  */
+      read_uleb128 (hdr_buf);
+      read_uleb128 (hdr_buf);
+
+      ++i;
+    }
+
+  return 1;
+}
+
+/* Read a single version 5 LNCT entry for a directory or file name in a
+   line header.  Sets *STRING to the resulting name, ignoring other
+   data.  Return 1 on success, 0 on failure.  */
+
+static int
+read_lnct (struct backtrace_state *state, struct dwarf_data *ddata,
+	   struct unit *u, struct dwarf_buf *hdr_buf,
+	   const struct line_header *hdr, size_t formats_count,
+	   const struct line_header_format *formats, const char **string)
+{
+  size_t i;
+  const char *dir;
+  const char *path;
+
+  dir = NULL;
+  path = NULL;
+  for (i = 0; i < formats_count; i++)
+    {
+      struct attr_val val;
+
+      if (!read_attribute (formats[i].form, 0, hdr_buf, u->is_dwarf64,
+			   u->version, hdr->addrsize, &ddata->dwarf_sections,
+			   ddata->altlink, &val))
+	return 0;
+      switch (formats[i].lnct)
+	{
+	case DW_LNCT_path:
+	  if (!resolve_string (&ddata->dwarf_sections, u->is_dwarf64,
+			       ddata->is_bigendian, u->str_offsets_base,
+			       &val, hdr_buf->error_callback, hdr_buf->data,
+			       &path))
+	    return 0;
+	  break;
+	case DW_LNCT_directory_index:
+	  if (val.encoding == ATTR_VAL_UINT)
+	    {
+	      if (val.u.uint >= hdr->dirs_count)
+		{
+		  dwarf_buf_error (hdr_buf,
+				   ("invalid directory index in "
+				    "line number program header"),
+				   0);
+		  return 0;
+		}
+	      dir = hdr->dirs[val.u.uint];
+	    }
+	  break;
+	default:
+	  /* We don't care about timestamps or sizes or hashes.  */
+	  break;
+	}
+    }
+
+  if (path == NULL)
+    {
+      dwarf_buf_error (hdr_buf,
+		       "missing file name in line number program header",
+		       0);
+      return 0;
+    }
+
+  if (dir == NULL)
+    *string = path;
+  else
+    {
+      size_t dir_len;
+      size_t path_len;
+      char *s;
+
+      dir_len = strlen (dir);
+      path_len = strlen (path);
+      s = (char *) backtrace_alloc (state, dir_len + path_len + 2,
+				    hdr_buf->error_callback, hdr_buf->data);
+      if (s == NULL)
+	return 0;
+      memcpy (s, dir, dir_len);
+      /* FIXME: If we are on a DOS-based file system, and the
+	 directory or the path name use backslashes, then we should
+	 use a backslash here.  */
+      s[dir_len] = '/';
+      memcpy (s + dir_len + 1, path, path_len + 1);
+      *string = s;
+    }
+
+  return 1;
+}
+
+/* Read a set of DWARF 5 line header format entries, setting *PCOUNT
+   and *PPATHS.  Return 1 on success, 0 on failure.  */
+
+static int
+read_line_header_format_entries (struct backtrace_state *state,
+				 struct dwarf_data *ddata,
+				 struct unit *u,
+				 struct dwarf_buf *hdr_buf,
+				 struct line_header *hdr,
+				 size_t *pcount,
+				 const char ***ppaths)
+{
+  size_t formats_count;
+  struct line_header_format *formats;
+  size_t paths_count;
+  const char **paths;
+  size_t i;
+  int ret;
+
+  formats_count = read_byte (hdr_buf);
+  if (formats_count == 0)
+    formats = NULL;
+  else
+    {
+      formats = ((struct line_header_format *)
+		 backtrace_alloc (state,
+				  (formats_count
+				   * sizeof (struct line_header_format)),
+				  hdr_buf->error_callback,
+				  hdr_buf->data));
+      if (formats == NULL)
+	return 0;
+
+      for (i = 0; i < formats_count; i++)
+	{
+	  formats[i].lnct = (int) read_uleb128(hdr_buf);
+	  formats[i].form = (enum dwarf_form) read_uleb128 (hdr_buf);
+	}
+    }
+
+  paths_count = read_uleb128 (hdr_buf);
+  if (paths_count == 0)
+    {
+      *pcount = 0;
+      *ppaths = NULL;
+      ret = 1;
+      goto exit;
+    }
+
+  paths = ((const char **)
+	   backtrace_alloc (state, paths_count * sizeof (const char *),
+			    hdr_buf->error_callback, hdr_buf->data));
+  if (paths == NULL)
+    {
+      ret = 0;
+      goto exit;
+    }
+  for (i = 0; i < paths_count; i++)
+    {
+      if (!read_lnct (state, ddata, u, hdr_buf, hdr, formats_count,
+		      formats, &paths[i]))
+	{
+	  backtrace_free (state, paths,
+			  paths_count * sizeof (const char *),
+			  hdr_buf->error_callback, hdr_buf->data);
+	  ret = 0;
+	  goto exit;
+	}
+    }
+
+  *pcount = paths_count;
+  *ppaths = paths;
+
+  ret = 1;
+
+ exit:
+  if (formats != NULL)
+    backtrace_free (state, formats,
+		    formats_count * sizeof (struct line_header_format),
+		    hdr_buf->error_callback, hdr_buf->data);
+
+  return  ret;
+}
+
+/* Read the line header.  Return 1 on success, 0 on failure.  */
+
+static int
+read_line_header (struct backtrace_state *state, struct dwarf_data *ddata,
+		  struct unit *u, int is_dwarf64, struct dwarf_buf *line_buf,
+		  struct line_header *hdr)
+{
+  uint64_t hdrlen;
+  struct dwarf_buf hdr_buf;
+
+  hdr->version = read_uint16 (line_buf);
+  if (hdr->version < 2 || hdr->version > 5)
+    {
+      dwarf_buf_error (line_buf, "unsupported line number version", -1);
+      return 0;
+    }
+
+  if (hdr->version < 5)
+    hdr->addrsize = u->addrsize;
+  else
+    {
+      hdr->addrsize = read_byte (line_buf);
+      /* We could support a non-zero segment_selector_size but I doubt
+	 we'll ever see it.  */
+      if (read_byte (line_buf) != 0)
+	{
+	  dwarf_buf_error (line_buf,
+			   "non-zero segment_selector_size not supported",
+			   -1);
+	  return 0;
+	}
+    }
+
+  hdrlen = read_offset (line_buf, is_dwarf64);
+
+  hdr_buf = *line_buf;
+  hdr_buf.left = hdrlen;
+
+  if (!advance (line_buf, hdrlen))
+    return 0;
+
+  hdr->min_insn_len = read_byte (&hdr_buf);
+  if (hdr->version < 4)
+    hdr->max_ops_per_insn = 1;
+  else
+    hdr->max_ops_per_insn = read_byte (&hdr_buf);
+
+  /* We don't care about default_is_stmt.  */
+  read_byte (&hdr_buf);
+
+  hdr->line_base = read_sbyte (&hdr_buf);
+  hdr->line_range = read_byte (&hdr_buf);
+
+  hdr->opcode_base = read_byte (&hdr_buf);
+  hdr->opcode_lengths = hdr_buf.buf;
+  if (!advance (&hdr_buf, hdr->opcode_base - 1))
+    return 0;
+
+  if (hdr->version < 5)
+    {
+      if (!read_v2_paths (state, u, &hdr_buf, hdr))
+	return 0;
+    }
+  else
+    {
+      if (!read_line_header_format_entries (state, ddata, u, &hdr_buf, hdr,
+					    &hdr->dirs_count,
+					    &hdr->dirs))
+	return 0;
+      if (!read_line_header_format_entries (state, ddata, u, &hdr_buf, hdr,
+					    &hdr->filenames_count,
+					    &hdr->filenames))
+	return 0;
+    }
+
+  if (hdr_buf.reported_underflow)
+    return 0;
+
+  return 1;
+}
+
+/* Read the line program, adding line mappings to VEC.  Return 1 on
+   success, 0 on failure.  */
+
+static int
+read_line_program (struct backtrace_state *state, struct dwarf_data *ddata,
+		   const struct line_header *hdr, struct dwarf_buf *line_buf,
+		   struct line_vector *vec)
+{
+  uint64_t address;
+  unsigned int op_index;
+  const char *reset_filename;
+  const char *filename;
+  int lineno;
+
+  address = 0;
+  op_index = 0;
+  if (hdr->filenames_count > 1)
+    reset_filename = hdr->filenames[1];
+  else
+    reset_filename = "";
+  filename = reset_filename;
+  lineno = 1;
+  while (line_buf->left > 0)
+    {
+      unsigned int op;
+
+      op = read_byte (line_buf);
+      if (op >= hdr->opcode_base)
+	{
+	  unsigned int advance;
+
+	  /* Special opcode.  */
+	  op -= hdr->opcode_base;
+	  advance = op / hdr->line_range;
+	  address += (hdr->min_insn_len * (op_index + advance)
+		      / hdr->max_ops_per_insn);
+	  op_index = (op_index + advance) % hdr->max_ops_per_insn;
+	  lineno += hdr->line_base + (int) (op % hdr->line_range);
+	  add_line (state, ddata, address, filename, lineno,
+		    line_buf->error_callback, line_buf->data, vec);
+	}
+      else if (op == DW_LNS_extended_op)
+	{
+	  uint64_t len;
+
+	  len = read_uleb128 (line_buf);
+	  op = read_byte (line_buf);
+	  switch (op)
+	    {
+	    case DW_LNE_end_sequence:
+	      /* FIXME: Should we mark the high PC here?  It seems
+		 that we already have that information from the
+		 compilation unit.  */
+	      address = 0;
+	      op_index = 0;
+	      filename = reset_filename;
+	      lineno = 1;
+	      break;
+	    case DW_LNE_set_address:
+	      address = read_address (line_buf, hdr->addrsize);
+	      break;
+	    case DW_LNE_define_file:
+	      {
+		const char *f;
+		unsigned int dir_index;
+
+		f = read_string (line_buf);
+		if (f == NULL)
+		  return 0;
+		dir_index = read_uleb128 (line_buf);
+		/* Ignore that time and length.  */
+		read_uleb128 (line_buf);
+		read_uleb128 (line_buf);
+		if (IS_ABSOLUTE_PATH (f))
+		  filename = f;
+		else
+		  {
+		    const char *dir;
+		    size_t dir_len;
+		    size_t f_len;
+		    char *p;
+
+		    if (dir_index < hdr->dirs_count)
+		      dir = hdr->dirs[dir_index];
+		    else
+		      {
+			dwarf_buf_error (line_buf,
+					 ("invalid directory index "
+					  "in line number program"),
+					 0);
+			return 0;
+		      }
+		    dir_len = strlen (dir);
+		    f_len = strlen (f);
+		    p = ((char *)
+			 backtrace_alloc (state, dir_len + f_len + 2,
+					  line_buf->error_callback,
+					  line_buf->data));
+		    if (p == NULL)
+		      return 0;
+		    memcpy (p, dir, dir_len);
+		    /* FIXME: If we are on a DOS-based file system,
+		       and the directory or the file name use
+		       backslashes, then we should use a backslash
+		       here.  */
+		    p[dir_len] = '/';
+		    memcpy (p + dir_len + 1, f, f_len + 1);
+		    filename = p;
+		  }
+	      }
+	      break;
+	    case DW_LNE_set_discriminator:
+	      /* We don't care about discriminators.  */
+	      read_uleb128 (line_buf);
+	      break;
+	    default:
+	      if (!advance (line_buf, len - 1))
+		return 0;
+	      break;
+	    }
+	}
+      else
+	{
+	  switch (op)
+	    {
+	    case DW_LNS_copy:
+	      add_line (state, ddata, address, filename, lineno,
+			line_buf->error_callback, line_buf->data, vec);
+	      break;
+	    case DW_LNS_advance_pc:
+	      {
+		uint64_t advance;
+
+		advance = read_uleb128 (line_buf);
+		address += (hdr->min_insn_len * (op_index + advance)
+			    / hdr->max_ops_per_insn);
+		op_index = (op_index + advance) % hdr->max_ops_per_insn;
+	      }
+	      break;
+	    case DW_LNS_advance_line:
+	      lineno += (int) read_sleb128 (line_buf);
+	      break;
+	    case DW_LNS_set_file:
+	      {
+		uint64_t fileno;
+
+		fileno = read_uleb128 (line_buf);
+		if (fileno >= hdr->filenames_count)
+		  {
+		    dwarf_buf_error (line_buf,
+				     ("invalid file number in "
+				      "line number program"),
+				     0);
+		    return 0;
+		  }
+		filename = hdr->filenames[fileno];
+	      }
+	      break;
+	    case DW_LNS_set_column:
+	      read_uleb128 (line_buf);
+	      break;
+	    case DW_LNS_negate_stmt:
+	      break;
+	    case DW_LNS_set_basic_block:
+	      break;
+	    case DW_LNS_const_add_pc:
+	      {
+		unsigned int advance;
+
+		op = 255 - hdr->opcode_base;
+		advance = op / hdr->line_range;
+		address += (hdr->min_insn_len * (op_index + advance)
+			    / hdr->max_ops_per_insn);
+		op_index = (op_index + advance) % hdr->max_ops_per_insn;
+	      }
+	      break;
+	    case DW_LNS_fixed_advance_pc:
+	      address += read_uint16 (line_buf);
+	      op_index = 0;
+	      break;
+	    case DW_LNS_set_prologue_end:
+	      break;
+	    case DW_LNS_set_epilogue_begin:
+	      break;
+	    case DW_LNS_set_isa:
+	      read_uleb128 (line_buf);
+	      break;
+	    default:
+	      {
+		unsigned int i;
+
+		for (i = hdr->opcode_lengths[op - 1]; i > 0; --i)
+		  read_uleb128 (line_buf);
+	      }
+	      break;
+	    }
+	}
+    }
+
+  return 1;
+}
+
+/* Read the line number information for a compilation unit.  Returns 1
+   on success, 0 on failure.  */
+
+static int
+read_line_info (struct backtrace_state *state, struct dwarf_data *ddata,
+		backtrace_error_callback error_callback, void *data,
+		struct unit *u, struct line_header *hdr, struct line **lines,
+		size_t *lines_count)
+{
+  struct line_vector vec;
+  struct dwarf_buf line_buf;
+  uint64_t len;
+  int is_dwarf64;
+  struct line *ln;
+
+  memset (&vec.vec, 0, sizeof vec.vec);
+  vec.count = 0;
+
+  memset (hdr, 0, sizeof *hdr);
+
+  if (u->lineoff != (off_t) (size_t) u->lineoff
+      || (size_t) u->lineoff >= ddata->dwarf_sections.size[DEBUG_LINE])
+    {
+      error_callback (data, "unit line offset out of range", 0);
+      goto fail;
+    }
+
+  line_buf.name = ".debug_line";
+  line_buf.start = ddata->dwarf_sections.data[DEBUG_LINE];
+  line_buf.buf = ddata->dwarf_sections.data[DEBUG_LINE] + u->lineoff;
+  line_buf.left = ddata->dwarf_sections.size[DEBUG_LINE] - u->lineoff;
+  line_buf.is_bigendian = ddata->is_bigendian;
+  line_buf.error_callback = error_callback;
+  line_buf.data = data;
+  line_buf.reported_underflow = 0;
+
+  len = read_initial_length (&line_buf, &is_dwarf64);
+  line_buf.left = len;
+
+  if (!read_line_header (state, ddata, u, is_dwarf64, &line_buf, hdr))
+    goto fail;
+
+  if (!read_line_program (state, ddata, hdr, &line_buf, &vec))
+    goto fail;
+
+  if (line_buf.reported_underflow)
+    goto fail;
+
+  if (vec.count == 0)
+    {
+      /* This is not a failure in the sense of a generating an error,
+	 but it is a failure in that sense that we have no useful
+	 information.  */
+      goto fail;
+    }
+
+  /* Allocate one extra entry at the end.  */
+  ln = ((struct line *)
+	backtrace_vector_grow (state, sizeof (struct line), error_callback,
+			       data, &vec.vec));
+  if (ln == NULL)
+    goto fail;
+  ln->pc = (uintptr_t) -1;
+  ln->filename = NULL;
+  ln->lineno = 0;
+  ln->idx = 0;
+
+  if (!backtrace_vector_release (state, &vec.vec, error_callback, data))
+    goto fail;
+
+  ln = (struct line *) vec.vec.base;
+  backtrace_qsort (ln, vec.count, sizeof (struct line), line_compare);
+
+  *lines = ln;
+  *lines_count = vec.count;
+
+  return 1;
+
+ fail:
+  backtrace_vector_free (state, &vec.vec, error_callback, data);
+  free_line_header (state, hdr, error_callback, data);
+  *lines = (struct line *) (uintptr_t) -1;
+  *lines_count = 0;
+  return 0;
+}
+
+static const char *read_referenced_name (struct dwarf_data *, struct unit *,
+					 uint64_t, backtrace_error_callback,
+					 void *);
+
+/* Read the name of a function from a DIE referenced by ATTR with VAL.  */
+
+static const char *
+read_referenced_name_from_attr (struct dwarf_data *ddata, struct unit *u,
+				struct attr *attr, struct attr_val *val,
+				backtrace_error_callback error_callback,
+				void *data)
+{
+  switch (attr->name)
+    {
+    case DW_AT_abstract_origin:
+    case DW_AT_specification:
+      break;
+    default:
+      return NULL;
+    }
+
+  if (attr->form == DW_FORM_ref_sig8)
+    return NULL;
+
+  if (val->encoding == ATTR_VAL_REF_INFO)
+    {
+      struct unit *unit
+	= find_unit (ddata->units, ddata->units_count,
+		     val->u.uint);
+      if (unit == NULL)
+	return NULL;
+
+      uint64_t offset = val->u.uint - unit->low_offset;
+      return read_referenced_name (ddata, unit, offset, error_callback, data);
+    }
+
+  if (val->encoding == ATTR_VAL_UINT
+      || val->encoding == ATTR_VAL_REF_UNIT)
+    return read_referenced_name (ddata, u, val->u.uint, error_callback, data);
+
+  if (val->encoding == ATTR_VAL_REF_ALT_INFO)
+    {
+      struct unit *alt_unit
+	= find_unit (ddata->altlink->units, ddata->altlink->units_count,
+		     val->u.uint);
+      if (alt_unit == NULL)
+	return NULL;
+
+      uint64_t offset = val->u.uint - alt_unit->low_offset;
+      return read_referenced_name (ddata->altlink, alt_unit, offset,
+				   error_callback, data);
+    }
+
+  return NULL;
+}
+
+/* Read the name of a function from a DIE referenced by a
+   DW_AT_abstract_origin or DW_AT_specification tag.  OFFSET is within
+   the same compilation unit.  */
+
+static const char *
+read_referenced_name (struct dwarf_data *ddata, struct unit *u,
+		      uint64_t offset, backtrace_error_callback error_callback,
+		      void *data)
+{
+  struct dwarf_buf unit_buf;
+  uint64_t code;
+  const struct abbrev *abbrev;
+  const char *ret;
+  size_t i;
+
+  /* OFFSET is from the start of the data for this compilation unit.
+     U->unit_data is the data, but it starts U->unit_data_offset bytes
+     from the beginning.  */
+
+  if (offset < u->unit_data_offset
+      || offset - u->unit_data_offset >= u->unit_data_len)
+    {
+      error_callback (data,
+		      "abstract origin or specification out of range",
+		      0);
+      return NULL;
+    }
+
+  offset -= u->unit_data_offset;
+
+  unit_buf.name = ".debug_info";
+  unit_buf.start = ddata->dwarf_sections.data[DEBUG_INFO];
+  unit_buf.buf = u->unit_data + offset;
+  unit_buf.left = u->unit_data_len - offset;
+  unit_buf.is_bigendian = ddata->is_bigendian;
+  unit_buf.error_callback = error_callback;
+  unit_buf.data = data;
+  unit_buf.reported_underflow = 0;
+
+  code = read_uleb128 (&unit_buf);
+  if (code == 0)
+    {
+      dwarf_buf_error (&unit_buf,
+		       "invalid abstract origin or specification",
+		       0);
+      return NULL;
+    }
+
+  abbrev = lookup_abbrev (&u->abbrevs, code, error_callback, data);
+  if (abbrev == NULL)
+    return NULL;
+
+  ret = NULL;
+  for (i = 0; i < abbrev->num_attrs; ++i)
+    {
+      struct attr_val val;
+
+      if (!read_attribute (abbrev->attrs[i].form, abbrev->attrs[i].val,
+			   &unit_buf, u->is_dwarf64, u->version, u->addrsize,
+			   &ddata->dwarf_sections, ddata->altlink, &val))
+	return NULL;
+
+      switch (abbrev->attrs[i].name)
+	{
+	case DW_AT_name:
+	  /* Third name preference: don't override.  A name we found in some
+	     other way, will normally be more useful -- e.g., this name is
+	     normally not mangled.  */
+	  if (ret != NULL)
+	    break;
+	  if (!resolve_string (&ddata->dwarf_sections, u->is_dwarf64,
+			       ddata->is_bigendian, u->str_offsets_base,
+			       &val, error_callback, data, &ret))
+	    return NULL;
+	  break;
+
+	case DW_AT_linkage_name:
+	case DW_AT_MIPS_linkage_name:
+	  /* First name preference: override all.  */
+	  {
+	    const char *s;
+
+	    s = NULL;
+	    if (!resolve_string (&ddata->dwarf_sections, u->is_dwarf64,
+				 ddata->is_bigendian, u->str_offsets_base,
+				 &val, error_callback, data, &s))
+	      return NULL;
+	    if (s != NULL)
+	      return s;
+	  }
+	  break;
+
+	case DW_AT_specification:
+	  /* Second name preference: override DW_AT_name, don't override
+	     DW_AT_linkage_name.  */
+	  {
+	    const char *name;
+
+	    name = read_referenced_name_from_attr (ddata, u, &abbrev->attrs[i],
+						   &val, error_callback, data);
+	    if (name != NULL)
+	      ret = name;
+	  }
+	  break;
+
+	default:
+	  break;
+	}
+    }
+
+  return ret;
+}
+
+/* Add a range to a unit that maps to a function.  This is called via
+   add_ranges.  Returns 1 on success, 0 on error.  */
+
+static int
+add_function_range (struct backtrace_state *state, void *rdata,
+		    uint64_t lowpc, uint64_t highpc,
+		    backtrace_error_callback error_callback, void *data,
+		    void *pvec)
+{
+  struct function *function = (struct function *) rdata;
+  struct function_vector *vec = (struct function_vector *) pvec;
+  struct function_addrs *p;
+
+  if (vec->count > 0)
+    {
+      p = (struct function_addrs *) vec->vec.base + (vec->count - 1);
+      if ((lowpc == p->high || lowpc == p->high + 1)
+	  && function == p->function)
+	{
+	  if (highpc > p->high)
+	    p->high = highpc;
+	  return 1;
+	}
+    }
+
+  p = ((struct function_addrs *)
+       backtrace_vector_grow (state, sizeof (struct function_addrs),
+			      error_callback, data, &vec->vec));
+  if (p == NULL)
+    return 0;
+
+  p->low = lowpc;
+  p->high = highpc;
+  p->function = function;
+
+  ++vec->count;
+
+  return 1;
+}
+
+/* Read one entry plus all its children.  Add function addresses to
+   VEC.  Returns 1 on success, 0 on error.  */
+
+static int
+read_function_entry (struct backtrace_state *state, struct dwarf_data *ddata,
+		     struct unit *u, uint64_t base, struct dwarf_buf *unit_buf,
+		     const struct line_header *lhdr,
+		     backtrace_error_callback error_callback, void *data,
+		     struct function_vector *vec_function,
+		     struct function_vector *vec_inlined)
+{
+  while (unit_buf->left > 0)
+    {
+      uint64_t code;
+      const struct abbrev *abbrev;
+      int is_function;
+      struct function *function;
+      struct function_vector *vec;
+      size_t i;
+      struct pcrange pcrange;
+      int have_linkage_name;
+
+      code = read_uleb128 (unit_buf);
+      if (code == 0)
+	return 1;
+
+      abbrev = lookup_abbrev (&u->abbrevs, code, error_callback, data);
+      if (abbrev == NULL)
+	return 0;
+
+      is_function = (abbrev->tag == DW_TAG_subprogram
+		     || abbrev->tag == DW_TAG_entry_point
+		     || abbrev->tag == DW_TAG_inlined_subroutine);
+
+      if (abbrev->tag == DW_TAG_inlined_subroutine)
+	vec = vec_inlined;
+      else
+	vec = vec_function;
+
+      function = NULL;
+      if (is_function)
+	{
+	  function = ((struct function *)
+		      backtrace_alloc (state, sizeof *function,
+				       error_callback, data));
+	  if (function == NULL)
+	    return 0;
+	  memset (function, 0, sizeof *function);
+	}
+
+      memset (&pcrange, 0, sizeof pcrange);
+      have_linkage_name = 0;
+      for (i = 0; i < abbrev->num_attrs; ++i)
+	{
+	  struct attr_val val;
+
+	  if (!read_attribute (abbrev->attrs[i].form, abbrev->attrs[i].val,
+			       unit_buf, u->is_dwarf64, u->version,
+			       u->addrsize, &ddata->dwarf_sections,
+			       ddata->altlink, &val))
+	    return 0;
+
+	  /* The compile unit sets the base address for any address
+	     ranges in the function entries.  */
+	  if ((abbrev->tag == DW_TAG_compile_unit
+	       || abbrev->tag == DW_TAG_skeleton_unit)
+	      && abbrev->attrs[i].name == DW_AT_low_pc)
+	    {
+	      if (val.encoding == ATTR_VAL_ADDRESS)
+		base = val.u.uint;
+	      else if (val.encoding == ATTR_VAL_ADDRESS_INDEX)
+		{
+		  if (!resolve_addr_index (&ddata->dwarf_sections,
+					   u->addr_base, u->addrsize,
+					   ddata->is_bigendian, val.u.uint,
+					   error_callback, data, &base))
+		    return 0;
+		}
+	    }
+
+	  if (is_function)
+	    {
+	      switch (abbrev->attrs[i].name)
+		{
+		case DW_AT_call_file:
+		  if (val.encoding == ATTR_VAL_UINT)
+		    {
+		      if (val.u.uint >= lhdr->filenames_count)
+			{
+			  dwarf_buf_error (unit_buf,
+					   ("invalid file number in "
+					    "DW_AT_call_file attribute"),
+					   0);
+			  return 0;
+			}
+		      function->caller_filename = lhdr->filenames[val.u.uint];
+		    }
+		  break;
+
+		case DW_AT_call_line:
+		  if (val.encoding == ATTR_VAL_UINT)
+		    function->caller_lineno = val.u.uint;
+		  break;
+
+		case DW_AT_abstract_origin:
+		case DW_AT_specification:
+		  /* Second name preference: override DW_AT_name, don't override
+		     DW_AT_linkage_name.  */
+		  if (have_linkage_name)
+		    break;
+		  {
+		    const char *name;
+
+		    name
+		      = read_referenced_name_from_attr (ddata, u,
+							&abbrev->attrs[i], &val,
+							error_callback, data);
+		    if (name != NULL)
+		      function->name = name;
+		  }
+		  break;
+
+		case DW_AT_name:
+		  /* Third name preference: don't override.  */
+		  if (function->name != NULL)
+		    break;
+		  if (!resolve_string (&ddata->dwarf_sections, u->is_dwarf64,
+				       ddata->is_bigendian,
+				       u->str_offsets_base, &val,
+				       error_callback, data, &function->name))
+		    return 0;
+		  break;
+
+		case DW_AT_linkage_name:
+		case DW_AT_MIPS_linkage_name:
+		  /* First name preference: override all.  */
+		  {
+		    const char *s;
+
+		    s = NULL;
+		    if (!resolve_string (&ddata->dwarf_sections, u->is_dwarf64,
+					 ddata->is_bigendian,
+					 u->str_offsets_base, &val,
+					 error_callback, data, &s))
+		      return 0;
+		    if (s != NULL)
+		      {
+			function->name = s;
+			have_linkage_name = 1;
+		      }
+		  }
+		  break;
+
+		case DW_AT_low_pc: case DW_AT_high_pc: case DW_AT_ranges:
+		  update_pcrange (&abbrev->attrs[i], &val, &pcrange);
+		  break;
+
+		default:
+		  break;
+		}
+	    }
+	}
+
+      /* If we couldn't find a name for the function, we have no use
+	 for it.  */
+      if (is_function && function->name == NULL)
+	{
+	  backtrace_free (state, function, sizeof *function,
+			  error_callback, data);
+	  is_function = 0;
+	}
+
+      if (is_function)
+	{
+	  if (pcrange.have_ranges
+	      || (pcrange.have_lowpc && pcrange.have_highpc))
+	    {
+	      if (!add_ranges (state, &ddata->dwarf_sections,
+			       ddata->base_address, ddata->is_bigendian,
+			       u, base, &pcrange, add_function_range,
+			       (void *) function, error_callback, data,
+			       (void *) vec))
+		return 0;
+	    }
+	  else
+	    {
+	      backtrace_free (state, function, sizeof *function,
+			      error_callback, data);
+	      is_function = 0;
+	    }
+	}
+
+      if (abbrev->has_children)
+	{
+	  if (!is_function)
+	    {
+	      if (!read_function_entry (state, ddata, u, base, unit_buf, lhdr,
+					error_callback, data, vec_function,
+					vec_inlined))
+		return 0;
+	    }
+	  else
+	    {
+	      struct function_vector fvec;
+
+	      /* Gather any information for inlined functions in
+		 FVEC.  */
+
+	      memset (&fvec, 0, sizeof fvec);
+
+	      if (!read_function_entry (state, ddata, u, base, unit_buf, lhdr,
+					error_callback, data, vec_function,
+					&fvec))
+		return 0;
+
+	      if (fvec.count > 0)
+		{
+		  struct function_addrs *p;
+		  struct function_addrs *faddrs;
+
+		  /* Allocate a trailing entry, but don't include it
+		     in fvec.count.  */
+		  p = ((struct function_addrs *)
+		       backtrace_vector_grow (state,
+					      sizeof (struct function_addrs),
+					      error_callback, data,
+					      &fvec.vec));
+		  if (p == NULL)
+		    return 0;
+		  p->low = 0;
+		  --p->low;
+		  p->high = p->low;
+		  p->function = NULL;
+
+		  if (!backtrace_vector_release (state, &fvec.vec,
+						 error_callback, data))
+		    return 0;
+
+		  faddrs = (struct function_addrs *) fvec.vec.base;
+		  backtrace_qsort (faddrs, fvec.count,
+				   sizeof (struct function_addrs),
+				   function_addrs_compare);
+
+		  function->function_addrs = faddrs;
+		  function->function_addrs_count = fvec.count;
+		}
+	    }
+	}
+    }
+
+  return 1;
+}
+
+/* Read function name information for a compilation unit.  We look
+   through the whole unit looking for function tags.  */
+
+static void
+read_function_info (struct backtrace_state *state, struct dwarf_data *ddata,
+		    const struct line_header *lhdr,
+		    backtrace_error_callback error_callback, void *data,
+		    struct unit *u, struct function_vector *fvec,
+		    struct function_addrs **ret_addrs,
+		    size_t *ret_addrs_count)
+{
+  struct function_vector lvec;
+  struct function_vector *pfvec;
+  struct dwarf_buf unit_buf;
+  struct function_addrs *p;
+  struct function_addrs *addrs;
+  size_t addrs_count;
+
+  /* Use FVEC if it is not NULL.  Otherwise use our own vector.  */
+  if (fvec != NULL)
+    pfvec = fvec;
+  else
+    {
+      memset (&lvec, 0, sizeof lvec);
+      pfvec = &lvec;
+    }
+
+  unit_buf.name = ".debug_info";
+  unit_buf.start = ddata->dwarf_sections.data[DEBUG_INFO];
+  unit_buf.buf = u->unit_data;
+  unit_buf.left = u->unit_data_len;
+  unit_buf.is_bigendian = ddata->is_bigendian;
+  unit_buf.error_callback = error_callback;
+  unit_buf.data = data;
+  unit_buf.reported_underflow = 0;
+
+  while (unit_buf.left > 0)
+    {
+      if (!read_function_entry (state, ddata, u, 0, &unit_buf, lhdr,
+				error_callback, data, pfvec, pfvec))
+	return;
+    }
+
+  if (pfvec->count == 0)
+    return;
+
+  /* Allocate a trailing entry, but don't include it in
+     pfvec->count.  */
+  p = ((struct function_addrs *)
+       backtrace_vector_grow (state, sizeof (struct function_addrs),
+			      error_callback, data, &pfvec->vec));
+  if (p == NULL)
+    return;
+  p->low = 0;
+  --p->low;
+  p->high = p->low;
+  p->function = NULL;
+
+  addrs_count = pfvec->count;
+
+  if (fvec == NULL)
+    {
+      if (!backtrace_vector_release (state, &lvec.vec, error_callback, data))
+	return;
+      addrs = (struct function_addrs *) pfvec->vec.base;
+    }
+  else
+    {
+      /* Finish this list of addresses, but leave the remaining space in
+	 the vector available for the next function unit.  */
+      addrs = ((struct function_addrs *)
+	       backtrace_vector_finish (state, &fvec->vec,
+					error_callback, data));
+      if (addrs == NULL)
+	return;
+      fvec->count = 0;
+    }
+
+  backtrace_qsort (addrs, addrs_count, sizeof (struct function_addrs),
+		   function_addrs_compare);
+
+  *ret_addrs = addrs;
+  *ret_addrs_count = addrs_count;
+}
+
+/* See if PC is inlined in FUNCTION.  If it is, print out the inlined
+   information, and update FILENAME and LINENO for the caller.
+   Returns whatever CALLBACK returns, or 0 to keep going.  */
+
+static int
+report_inlined_functions (uintptr_t pc, struct function *function,
+			  backtrace_full_callback callback, void *data,
+			  const char **filename, int *lineno)
+{
+  struct function_addrs *p;
+  struct function_addrs *match;
+  struct function *inlined;
+  int ret;
+
+  if (function->function_addrs_count == 0)
+    return 0;
+
+  /* Our search isn't safe if pc == -1, as that is the sentinel
+     value.  */
+  if (pc + 1 == 0)
+    return 0;
+
+  p = ((struct function_addrs *)
+       bsearch (&pc, function->function_addrs,
+		function->function_addrs_count,
+		sizeof (struct function_addrs),
+		function_addrs_search));
+  if (p == NULL)
+    return 0;
+
+  /* Here pc >= p->low && pc < (p + 1)->low.  The function_addrs are
+     sorted by low, so if pc > p->low we are at the end of a range of
+     function_addrs with the same low value.  If pc == p->low walk
+     forward to the end of the range with that low value.  Then walk
+     backward and use the first range that includes pc.  */
+  while (pc == (p + 1)->low)
+    ++p;
+  match = NULL;
+  while (1)
+    {
+      if (pc < p->high)
+	{
+	  match = p;
+	  break;
+	}
+      if (p == function->function_addrs)
+	break;
+      if ((p - 1)->low < p->low)
+	break;
+      --p;
+    }
+  if (match == NULL)
+    return 0;
+
+  /* We found an inlined call.  */
+
+  inlined = match->function;
+
+  /* Report any calls inlined into this one.  */
+  ret = report_inlined_functions (pc, inlined, callback, data,
+				  filename, lineno);
+  if (ret != 0)
+    return ret;
+
+  /* Report this inlined call.  */
+  ret = callback (data, pc, *filename, *lineno, inlined->name);
+  if (ret != 0)
+    return ret;
+
+  /* Our caller will report the caller of the inlined function; tell
+     it the appropriate filename and line number.  */
+  *filename = inlined->caller_filename;
+  *lineno = inlined->caller_lineno;
+
+  return 0;
+}
+
+/* Look for a PC in the DWARF mapping for one module.  On success,
+   call CALLBACK and return whatever it returns.  On error, call
+   ERROR_CALLBACK and return 0.  Sets *FOUND to 1 if the PC is found,
+   0 if not.  */
+
+static int
+dwarf_lookup_pc (struct backtrace_state *state, struct dwarf_data *ddata,
+		 uintptr_t pc, backtrace_full_callback callback,
+		 backtrace_error_callback error_callback, void *data,
+		 int *found)
+{
+  struct unit_addrs *entry;
+  int found_entry;
+  struct unit *u;
+  int new_data;
+  struct line *lines;
+  struct line *ln;
+  struct function_addrs *p;
+  struct function_addrs *fmatch;
+  struct function *function;
+  const char *filename;
+  int lineno;
+  int ret;
+
+  *found = 1;
+
+  /* Find an address range that includes PC.  Our search isn't safe if
+     PC == -1, as we use that as a sentinel value, so skip the search
+     in that case.  */
+  entry = (ddata->addrs_count == 0 || pc + 1 == 0
+	   ? NULL
+	   : bsearch (&pc, ddata->addrs, ddata->addrs_count,
+		      sizeof (struct unit_addrs), unit_addrs_search));
+
+  if (entry == NULL)
+    {
+      *found = 0;
+      return 0;
+    }
+
+  /* Here pc >= entry->low && pc < (entry + 1)->low.  The unit_addrs
+     are sorted by low, so if pc > p->low we are at the end of a range
+     of unit_addrs with the same low value.  If pc == p->low walk
+     forward to the end of the range with that low value.  Then walk
+     backward and use the first range that includes pc.  */
+  while (pc == (entry + 1)->low)
+    ++entry;
+  found_entry = 0;
+  while (1)
+    {
+      if (pc < entry->high)
+	{
+	  found_entry = 1;
+	  break;
+	}
+      if (entry == ddata->addrs)
+	break;
+      if ((entry - 1)->low < entry->low)
+	break;
+      --entry;
+    }
+  if (!found_entry)
+    {
+      *found = 0;
+      return 0;
+    }
+
+  /* We need the lines, lines_count, function_addrs,
+     function_addrs_count fields of u.  If they are not set, we need
+     to set them.  When running in threaded mode, we need to allow for
+     the possibility that some other thread is setting them
+     simultaneously.  */
+
+  u = entry->u;
+  lines = u->lines;
+
+  /* Skip units with no useful line number information by walking
+     backward.  Useless line number information is marked by setting
+     lines == -1.  */
+  while (entry > ddata->addrs
+	 && pc >= (entry - 1)->low
+	 && pc < (entry - 1)->high)
+    {
+      if (state->threaded)
+	lines = (struct line *) backtrace_atomic_load_pointer (&u->lines);
+
+      if (lines != (struct line *) (uintptr_t) -1)
+	break;
+
+      --entry;
+
+      u = entry->u;
+      lines = u->lines;
+    }
+
+  if (state->threaded)
+    lines = backtrace_atomic_load_pointer (&u->lines);
+
+  new_data = 0;
+  if (lines == NULL)
+    {
+      struct function_addrs *function_addrs;
+      size_t function_addrs_count;
+      struct line_header lhdr;
+      size_t count;
+
+      /* We have never read the line information for this unit.  Read
+	 it now.  */
+
+      function_addrs = NULL;
+      function_addrs_count = 0;
+      if (read_line_info (state, ddata, error_callback, data, entry->u, &lhdr,
+			  &lines, &count))
+	{
+	  struct function_vector *pfvec;
+
+	  /* If not threaded, reuse DDATA->FVEC for better memory
+	     consumption.  */
+	  if (state->threaded)
+	    pfvec = NULL;
+	  else
+	    pfvec = &ddata->fvec;
+	  read_function_info (state, ddata, &lhdr, error_callback, data,
+			      entry->u, pfvec, &function_addrs,
+			      &function_addrs_count);
+	  free_line_header (state, &lhdr, error_callback, data);
+	  new_data = 1;
+	}
+
+      /* Atomically store the information we just read into the unit.
+	 If another thread is simultaneously writing, it presumably
+	 read the same information, and we don't care which one we
+	 wind up with; we just leak the other one.  We do have to
+	 write the lines field last, so that the acquire-loads above
+	 ensure that the other fields are set.  */
+
+      if (!state->threaded)
+	{
+	  u->lines_count = count;
+	  u->function_addrs = function_addrs;
+	  u->function_addrs_count = function_addrs_count;
+	  u->lines = lines;
+	}
+      else
+	{
+	  backtrace_atomic_store_size_t (&u->lines_count, count);
+	  backtrace_atomic_store_pointer (&u->function_addrs, function_addrs);
+	  backtrace_atomic_store_size_t (&u->function_addrs_count,
+					 function_addrs_count);
+	  backtrace_atomic_store_pointer (&u->lines, lines);
+	}
+    }
+
+  /* Now all fields of U have been initialized.  */
+
+  if (lines == (struct line *) (uintptr_t) -1)
+    {
+      /* If reading the line number information failed in some way,
+	 try again to see if there is a better compilation unit for
+	 this PC.  */
+      if (new_data)
+	return dwarf_lookup_pc (state, ddata, pc, callback, error_callback,
+				data, found);
+      return callback (data, pc, NULL, 0, NULL);
+    }
+
+  /* Search for PC within this unit.  */
+
+  ln = (struct line *) bsearch (&pc, lines, entry->u->lines_count,
+				sizeof (struct line), line_search);
+  if (ln == NULL)
+    {
+      /* The PC is between the low_pc and high_pc attributes of the
+	 compilation unit, but no entry in the line table covers it.
+	 This implies that the start of the compilation unit has no
+	 line number information.  */
+
+      if (entry->u->abs_filename == NULL)
+	{
+	  const char *filename;
+
+	  filename = entry->u->filename;
+	  if (filename != NULL
+	      && !IS_ABSOLUTE_PATH (filename)
+	      && entry->u->comp_dir != NULL)
+	    {
+	      size_t filename_len;
+	      const char *dir;
+	      size_t dir_len;
+	      char *s;
+
+	      filename_len = strlen (filename);
+	      dir = entry->u->comp_dir;
+	      dir_len = strlen (dir);
+	      s = (char *) backtrace_alloc (state, dir_len + filename_len + 2,
+					    error_callback, data);
+	      if (s == NULL)
+		{
+		  *found = 0;
+		  return 0;
+		}
+	      memcpy (s, dir, dir_len);
+	      /* FIXME: Should use backslash if DOS file system.  */
+	      s[dir_len] = '/';
+	      memcpy (s + dir_len + 1, filename, filename_len + 1);
+	      filename = s;
+	    }
+	  entry->u->abs_filename = filename;
+	}
+
+      return callback (data, pc, entry->u->abs_filename, 0, NULL);
+    }
+
+  /* Search for function name within this unit.  */
+
+  if (entry->u->function_addrs_count == 0)
+    return callback (data, pc, ln->filename, ln->lineno, NULL);
+
+  p = ((struct function_addrs *)
+       bsearch (&pc, entry->u->function_addrs,
+		entry->u->function_addrs_count,
+		sizeof (struct function_addrs),
+		function_addrs_search));
+  if (p == NULL)
+    return callback (data, pc, ln->filename, ln->lineno, NULL);
+
+  /* Here pc >= p->low && pc < (p + 1)->low.  The function_addrs are
+     sorted by low, so if pc > p->low we are at the end of a range of
+     function_addrs with the same low value.  If pc == p->low walk
+     forward to the end of the range with that low value.  Then walk
+     backward and use the first range that includes pc.  */
+  while (pc == (p + 1)->low)
+    ++p;
+  fmatch = NULL;
+  while (1)
+    {
+      if (pc < p->high)
+	{
+	  fmatch = p;
+	  break;
+	}
+      if (p == entry->u->function_addrs)
+	break;
+      if ((p - 1)->low < p->low)
+	break;
+      --p;
+    }
+  if (fmatch == NULL)
+    return callback (data, pc, ln->filename, ln->lineno, NULL);
+
+  function = fmatch->function;
+
+  filename = ln->filename;
+  lineno = ln->lineno;
+
+  ret = report_inlined_functions (pc, function, callback, data,
+				  &filename, &lineno);
+  if (ret != 0)
+    return ret;
+
+  return callback (data, pc, filename, lineno, function->name);
+}
+
+
+/* Return the file/line information for a PC using the DWARF mapping
+   we built earlier.  */
+
+static int
+dwarf_fileline (struct backtrace_state *state, uintptr_t pc,
+		backtrace_full_callback callback,
+		backtrace_error_callback error_callback, void *data)
+{
+  struct dwarf_data *ddata;
+  int found;
+  int ret;
+
+  if (!state->threaded)
+    {
+      for (ddata = (struct dwarf_data *) state->fileline_data;
+	   ddata != NULL;
+	   ddata = ddata->next)
+	{
+	  ret = dwarf_lookup_pc (state, ddata, pc, callback, error_callback,
+				 data, &found);
+	  if (ret != 0 || found)
+	    return ret;
+	}
+    }
+  else
+    {
+      struct dwarf_data **pp;
+
+      pp = (struct dwarf_data **) (void *) &state->fileline_data;
+      while (1)
+	{
+	  ddata = backtrace_atomic_load_pointer (pp);
+	  if (ddata == NULL)
+	    break;
+
+	  ret = dwarf_lookup_pc (state, ddata, pc, callback, error_callback,
+				 data, &found);
+	  if (ret != 0 || found)
+	    return ret;
+
+	  pp = &ddata->next;
+	}
+    }
+
+  /* FIXME: See if any libraries have been dlopen'ed.  */
+
+  return callback (data, pc, NULL, 0, NULL);
+}
+
+/* Initialize our data structures from the DWARF debug info for a
+   file.  Return NULL on failure.  */
+
+static struct dwarf_data *
+build_dwarf_data (struct backtrace_state *state,
+		  uintptr_t base_address,
+		  const struct dwarf_sections *dwarf_sections,
+		  int is_bigendian,
+		  struct dwarf_data *altlink,
+		  backtrace_error_callback error_callback,
+		  void *data)
+{
+  struct unit_addrs_vector addrs_vec;
+  struct unit_addrs *addrs;
+  size_t addrs_count;
+  struct unit_vector units_vec;
+  struct unit **units;
+  size_t units_count;
+  struct dwarf_data *fdata;
+
+  if (!build_address_map (state, base_address, dwarf_sections, is_bigendian,
+			  altlink, error_callback, data, &addrs_vec,
+			  &units_vec))
+    return NULL;
+
+  if (!backtrace_vector_release (state, &addrs_vec.vec, error_callback, data))
+    return NULL;
+  if (!backtrace_vector_release (state, &units_vec.vec, error_callback, data))
+    return NULL;
+  addrs = (struct unit_addrs *) addrs_vec.vec.base;
+  units = (struct unit **) units_vec.vec.base;
+  addrs_count = addrs_vec.count;
+  units_count = units_vec.count;
+  backtrace_qsort (addrs, addrs_count, sizeof (struct unit_addrs),
+		   unit_addrs_compare);
+  /* No qsort for units required, already sorted.  */
+
+  fdata = ((struct dwarf_data *)
+	   backtrace_alloc (state, sizeof (struct dwarf_data),
+			    error_callback, data));
+  if (fdata == NULL)
+    return NULL;
+
+  fdata->next = NULL;
+  fdata->altlink = altlink;
+  fdata->base_address = base_address;
+  fdata->addrs = addrs;
+  fdata->addrs_count = addrs_count;
+  fdata->units = units;
+  fdata->units_count = units_count;
+  fdata->dwarf_sections = *dwarf_sections;
+  fdata->is_bigendian = is_bigendian;
+  memset (&fdata->fvec, 0, sizeof fdata->fvec);
+
+  return fdata;
+}
+
+/* Build our data structures from the DWARF sections for a module.
+   Set FILELINE_FN and STATE->FILELINE_DATA.  Return 1 on success, 0
+   on failure.  */
+
+int
+backtrace_dwarf_add (struct backtrace_state *state,
+		     uintptr_t base_address,
+		     const struct dwarf_sections *dwarf_sections,
+		     int is_bigendian,
+		     struct dwarf_data *fileline_altlink,
+		     backtrace_error_callback error_callback,
+		     void *data, fileline *fileline_fn,
+		     struct dwarf_data **fileline_entry)
+{
+  struct dwarf_data *fdata;
+
+  fdata = build_dwarf_data (state, base_address, dwarf_sections, is_bigendian,
+			    fileline_altlink, error_callback, data);
+  if (fdata == NULL)
+    return 0;
+
+  if (fileline_entry != NULL)
+    *fileline_entry = fdata;
+
+  if (!state->threaded)
+    {
+      struct dwarf_data **pp;
+
+      for (pp = (struct dwarf_data **) (void *) &state->fileline_data;
+	   *pp != NULL;
+	   pp = &(*pp)->next)
+	;
+      *pp = fdata;
+    }
+  else
+    {
+      while (1)
+	{
+	  struct dwarf_data **pp;
+
+	  pp = (struct dwarf_data **) (void *) &state->fileline_data;
+
+	  while (1)
+	    {
+	      struct dwarf_data *p;
+
+	      p = backtrace_atomic_load_pointer (pp);
+
+	      if (p == NULL)
+		break;
+
+	      pp = &p->next;
+	    }
+
+	  if (__sync_bool_compare_and_swap (pp, NULL, fdata))
+	    break;
+	}
+    }
+
+  *fileline_fn = dwarf_fileline;
+
+  return 1;
+}