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+# ===========================================================================
+# http://www.gnu.org/software/autoconf-archive/ax_check_vscript.html
+# ===========================================================================
+#
+# SYNOPSIS
+#
+# AX_CHECK_VSCRIPT
+#
+# DESCRIPTION
+#
+# Check whether the linker supports version scripts. Version scripts are
+# used when building shared libraries to bind symbols to version nodes
+# (helping to detect incompatibilities) or to limit the visibility of
+# non-public symbols.
+#
+# Output:
+#
+# If version scripts are supported, VSCRIPT_LDFLAGS will contain the
+# appropriate flag to pass to the linker. On GNU systems this would
+# typically be "-Wl,--version-script", and on Solaris it would typically
+# be "-Wl,-M".
+#
+# Two Automake conditionals are also set:
+#
+# HAVE_VSCRIPT is true if the linker supports version scripts with
+# entries that use simple wildcards, like "local: *".
+#
+# HAVE_VSCRIPT_COMPLEX is true if the linker supports version scripts with
+# pattern matching wildcards, like "global: Java_*".
+#
+# On systems that do not support symbol versioning, such as Mac OS X, both
+# conditionals will be false. They will also be false if the user passes
+# "--disable-symvers" on the configure command line.
+#
+# Example:
+#
+# configure.ac:
+#
+# AX_CHECK_VSCRIPT
+#
+# Makefile.am:
+#
+# if HAVE_VSCRIPT
+# libfoo_la_LDFLAGS += $(VSCRIPT_LDFLAGS),@srcdir@/libfoo.map
+# endif
+#
+# if HAVE_VSCRIPT_COMPLEX
+# libbar_la_LDFLAGS += $(VSCRIPT_LDFLAGS),@srcdir@/libbar.map
+# endif
+#
+# LICENSE
+#
+# Copyright (c) 2014 Kevin Cernekee <cernekee@gmail.com>
+#
+# Copying and distribution of this file, with or without modification, are
+# permitted in any medium without royalty provided the copyright notice
+# and this notice are preserved. This file is offered as-is, without any
+# warranty.
+
+#serial 1
+
+# _AX_CHECK_VSCRIPT(flag, global-sym, action-if-link-succeeds, [junk-file=no])
+AC_DEFUN([_AX_CHECK_VSCRIPT], [
+ AC_LANG_PUSH([C])
+ ax_check_vscript_save_flags="$LDFLAGS"
+ echo "V1 { global: $2; local: *; };" > conftest.map
+ AS_IF([test x$4 = xyes], [
+ echo "{" >> conftest.map
+ ])
+ LDFLAGS="$LDFLAGS -Wl,$1,conftest.map"
+ AC_LINK_IFELSE([AC_LANG_PROGRAM([[int show, hide;]], [])], [$3])
+ LDFLAGS="$ax_check_vscript_save_flags"
+ rm -f conftest.map
+ AC_LANG_POP([C])
+]) dnl _AX_CHECK_VSCRIPT
+
+AC_DEFUN([AX_CHECK_VSCRIPT], [
+
+ AC_ARG_ENABLE([symvers],
+ AS_HELP_STRING([--disable-symvers],
+ [disable library symbol versioning [default=auto]]),
+ [want_symvers=$enableval],
+ [want_symvers=yes]
+ )
+
+ AS_IF([test x$want_symvers = xyes], [
+
+ dnl First test --version-script and -M with a simple wildcard.
+
+ AC_CACHE_CHECK([linker version script flag], ax_cv_check_vscript_flag, [
+ ax_cv_check_vscript_flag=unsupported
+ _AX_CHECK_VSCRIPT([--version-script], [show], [
+ ax_cv_check_vscript_flag=--version-script
+ ])
+ AS_IF([test x$ax_cv_check_vscript_flag = xunsupported], [
+ _AX_CHECK_VSCRIPT([-M], [show], [ax_cv_check_vscript_flag=-M])
+ ])
+
+ dnl The linker may interpret -M (no argument) as "produce a load map."
+ dnl If "-M conftest.map" doesn't fail when conftest.map contains
+ dnl obvious syntax errors, assume this is the case.
+
+ AS_IF([test x$ax_cv_check_vscript_flag != xunsupported], [
+ _AX_CHECK_VSCRIPT([$ax_cv_check_vscript_flag], [show],
+ [ax_cv_check_vscript_flag=unsupported], [yes])
+ ])
+ ])
+
+ dnl If the simple wildcard worked, retest with a complex wildcard.
+
+ AS_IF([test x$ax_cv_check_vscript_flag != xunsupported], [
+ ax_check_vscript_flag=$ax_cv_check_vscript_flag
+ AC_CACHE_CHECK([if version scripts can use complex wildcards],
+ ax_cv_check_vscript_complex_wildcards, [
+ ax_cv_check_vscript_complex_wildcards=no
+ _AX_CHECK_VSCRIPT([$ax_cv_check_vscript_flag], [sh*], [
+ ax_cv_check_vscript_complex_wildcards=yes])
+ ])
+ ax_check_vscript_complex_wildcards="$ax_cv_check_vscript_complex_wildcards"
+ ], [
+ ax_check_vscript_flag=
+ ax_check_vscript_complex_wildcards=no
+ ])
+ ], [
+ AC_MSG_CHECKING([linker version script flag])
+ AC_MSG_RESULT([disabled])
+
+ ax_check_vscript_flag=
+ ax_check_vscript_complex_wildcards=no
+ ])
+
+ AS_IF([test x$ax_check_vscript_flag != x], [
+ VSCRIPT_LDFLAGS="-Wl,$ax_check_vscript_flag"
+ AC_SUBST([VSCRIPT_LDFLAGS])
+ ])
+
+ AM_CONDITIONAL([HAVE_VSCRIPT],
+ [test x$ax_check_vscript_flag != x])
+ AM_CONDITIONAL([HAVE_VSCRIPT_COMPLEX],
+ [test x$ax_check_vscript_complex_wildcards = xyes])
+
+]) dnl AX_CHECK_VSCRIPT