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Diffstat (limited to 'include/haproxy/compiler.h')
| -rw-r--r-- | include/haproxy/compiler.h | 469 |
1 files changed, 469 insertions, 0 deletions
diff --git a/include/haproxy/compiler.h b/include/haproxy/compiler.h new file mode 100644 index 0000000..d8e8a72 --- /dev/null +++ b/include/haproxy/compiler.h @@ -0,0 +1,469 @@ +/* + * include/haproxy/compiler.h + * This files contains some compiler-specific settings. + * + * Copyright (C) 2000-2020 Willy Tarreau - w@1wt.eu + * + * This library is free software; you can redistribute it and/or + * modify it under the terms of the GNU Lesser General Public + * License as published by the Free Software Foundation, version 2.1 + * exclusively. + * + * This library is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU + * Lesser General Public License for more details. + * + * You should have received a copy of the GNU Lesser General Public + * License along with this library; if not, write to the Free Software + * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA + */ + +#ifndef _HAPROXY_COMPILER_H +#define _HAPROXY_COMPILER_H + +/* leave a chance to the compiler to bring its own definitions first; this + * will cause cdefs.h to be included on systems which have it. + */ +#include <inttypes.h> + +#ifdef DEBUG_USE_ABORT +#include <stdlib.h> +#endif + +/* + * Gcc before 3.0 needs [0] to declare a variable-size array + */ +#ifndef VAR_ARRAY +#if defined(__GNUC__) && (__GNUC__ < 3) +#define VAR_ARRAY 0 +#else +#define VAR_ARRAY +#endif +#endif + +/* This is used to test if a macro is defined and equals 1. The principle is + * that the macro is passed as a value and its value concatenated to the word + * "comma_for_one" to form a new macro name. The macro "comma_for_one1" equals + * one comma, which, once used in an argument, will shift all of them by one, + * so that we can use this to concatenate both a 1 and a 0 and always pick the + * second one. + */ +#define comma_for_one1 , +#define _____equals_1(x, y, ...) (y) +#define ____equals_1(x, ...) _____equals_1(x, 0) +#define ___equals_1(x) ____equals_1(comma_for_one ## x 1) +#define __equals_1(x) ___equals_1(x) + +/* gcc 5 and clang 3 brought __has_attribute(), which is not well documented in + * the case of gcc, but is convenient since handled at the preprocessor level. + * In both cases it's possible to test for __has_attribute() using ifdef. When + * not defined we remap this to the __has_attribute_<name> macro so that we'll + * later be able to implement on a per-compiler basis those which are missing, + * by defining __has_attribute_<name> to 1. + */ +#ifndef __has_attribute +#define __has_attribute(x) __equals_1(__has_attribute_ ## x) +#endif + +/* The fallthrough attribute arrived with gcc 7, the same version that started + * to emit the fallthrough warnings and to parse the comments. Comments do not + * manage to stop the warning when preprocessing is split from compiling (e.g. + * when building under distcc). Better encourage the use of a __fallthrough + * statement instead. There are still limitations in that clang doesn't accept + * it after a label; this is the reason why we're always preceding it with an + * empty do-while. + */ +#if __has_attribute(fallthrough) +# define __fallthrough do { } while (0); __attribute__((fallthrough)) +#else +# define __fallthrough do { } while (0) +#endif + +#if !defined(__GNUC__) +/* Some versions of glibc irresponsibly redefine __attribute__() to empty for + * non-gcc compilers, and as such, silently break all constructors with other + * other compilers. Let's make sure such incompatibilities are detected if any, + * or that the attribute is properly enforced. + */ +#undef __attribute__ +#define __attribute__(x) __attribute__(x) +#endif + +/* attribute(warning) was added in gcc 4.3 */ +#if defined(__GNUC__) && (__GNUC__ > 4 || (__GNUC__ == 4 && __GNUC_MINOR__ >= 3)) +# define __has_attribute_warning 1 +#endif + +/* __attribute__warning(x) does __attribute__((warning(x))) if supported by the + * compiler, otherwise __attribute__((deprecated)). Clang supports it since v14 + * but is a bit capricious in that it refuses a redefinition with a warning + * attribute that wasn't there the first time. However it's OK with deprecated(x) + * so better use this one. See: https://github.com/llvm/llvm-project/issues/56519 + */ +#if defined(__clang__) +# define __attribute__warning(x) __attribute__((deprecated(x))) +#elif __has_attribute(warning) +# define __attribute__warning(x) __attribute__((warning(x))) +#else +# define __attribute__warning(x) __attribute__((deprecated)) +#endif + +/* By default, gcc does not inline large chunks of code, but we want it to + * respect our choices. + */ +#if !defined(forceinline) +#if !defined(__GNUC__) || (__GNUC__ < 3) +#define forceinline inline +#else +#define forceinline inline __attribute__((always_inline)) +#endif +#endif + +#ifndef __maybe_unused +/* silence the "unused" warnings without having to place painful #ifdefs. + * For use with variables or functions. + */ +#define __maybe_unused __attribute__((unused)) +#endif + +/* TCC doesn't support weak attribute, sections etc and needs the more portable + * obsolete linker model instead. + */ +#if defined(__TINYC__) && !defined(USE_OBSOLETE_LINKER) +#define USE_OBSOLETE_LINKER 1 +#endif + +/* These macros are used to declare a section name for a variable. + * WARNING: keep section names short, as MacOS limits them to 16 characters. + * The _START and _STOP attributes have to be placed after the start and stop + * weak symbol declarations, and are only used by MacOS. + */ +#if !defined(USE_OBSOLETE_LINKER) + +#ifdef __APPLE__ +#define HA_SECTION(s) __attribute__((__section__("__DATA, " s))) +#define HA_SECTION_START(s) __asm("section$start$__DATA$" s) +#define HA_SECTION_STOP(s) __asm("section$end$__DATA$" s) +#else +#define HA_SECTION(s) __attribute__((__section__(s))) +#define HA_SECTION_START(s) +#define HA_SECTION_STOP(s) +#endif + +#else // obsolete linker below, let's just not force any section + +#define HA_SECTION(s) +#define HA_SECTION_START(s) +#define HA_SECTION_STOP(s) + +#endif // USE_OBSOLETE_LINKER + +/* Declare a symbol as weak if possible, otherwise global. Since we don't want to + * error on multiple definitions, the symbol is declared weak. On MacOS ".weak" + * does not exist and we must continue to use ".globl" instead. Note that + * ".global" is to be avoided on other platforms as llvm complains about it + * being used for symbols declared as weak elsewhere in the code. It may or may + * not work depending on linkers and assemblers, this is only for advanced use + * anyway (and most likely it will only work with !USE_OBSOLETE_LINKER). + */ +#if defined(__APPLE__) +# define __HA_WEAK(sym) __asm__(".globl " #sym) +#else +# define __HA_WEAK(sym) __asm__(".weak " #sym) +#endif +#define HA_WEAK(sym) __HA_WEAK(sym) + +/* declare a symbol as global */ +#define __HA_GLOBL(sym) __asm__(".globl " #sym) +#define HA_GLOBL(sym) __HA_GLOBL(sym) + +/* use this attribute on a variable to move it to the read_mostly section */ +#if !defined(__read_mostly) +#define __read_mostly HA_SECTION("read_mostly") +#endif + +/* This allows gcc to know that some locations are never reached, for example + * after a longjmp() in the Lua code, hence that some errors caught by such + * methods cannot propagate further. This is important with gcc versions 6 and + * above which can more aggressively detect null dereferences. The builtin + * below was introduced in gcc 4.5, and before it we didn't care. + */ +#ifdef DEBUG_USE_ABORT +#define my_unreachable() abort() +#else +#if defined(__GNUC__) && (__GNUC__ >= 5 || (__GNUC__ == 4 && __GNUC_MINOR__ >= 5)) +#define my_unreachable() __builtin_unreachable() +#else +#define my_unreachable() do { } while (1) +#endif +#endif + +/* This prevents the compiler from folding multiple identical code paths into a + * single one, by adding a dependency on the line number in the path. This may + * typically happen on function tails, or purposely placed abort() before an + * unreachable() statement, due to the compiler performing an Identical Code + * Folding optimization. This macro is aimed at helping with code tracing in + * crash dumps and may also be used for specific optimizations. One known case + * is gcc-4.7 and 4.8 which aggressively fold multiple ABORT_NOW() exit points + * and which causes wrong line numbers to be reported by the debugger (note + * that even newer compilers do this when using abort()). Please keep in mind + * that nothing prevents the compiler from folding the code after that point, + * but at least it will not fold the code before. + */ +#define DO_NOT_FOLD() do { asm volatile("" :: "i"(__LINE__)); } while (0) + +/* This macro may be used to block constant propagation that lets the compiler + * detect a possible NULL dereference on a variable resulting from an explicit + * assignment in an impossible check. Sometimes a function is called which does + * safety checks and returns NULL if safe conditions are not met. The place + * where it's called cannot hit this condition and dereferencing the pointer + * without first checking it will make the compiler emit a warning about a + * "potential null pointer dereference" which is hard to work around. This + * macro "washes" the pointer and prevents the compiler from emitting tests + * branching to undefined instructions. It may only be used when the developer + * is absolutely certain that the conditions are guaranteed and that the + * pointer passed in argument cannot be NULL by design. + */ +#define ALREADY_CHECKED(p) do { asm("" : "=rm"(p) : "0"(p)); } while (0) + +/* same as above but to be used to pass the input value to the output but + * without letting the compiler know about its initial properties. + */ +#define DISGUISE(v) ({ typeof(v) __v = (v); ALREADY_CHECKED(__v); __v; }) + +/* Implements a static event counter where it's used. This is typically made to + * report some warnings only once, either during boot or at runtime. It only + * returns true on the very first call, and zero later. It's thread-safe and + * uses a single byte of memory per call place. It relies on the atomic xchg + * defined in atomic.h which is also part of the common API. + */ +#define ONLY_ONCE() ({ static char __cnt; !_HA_ATOMIC_XCHG(&__cnt, 1); }) + +/* makes a string from a constant (number or macro), avoids the need for + * printf("%d") format just to dump a setting limit or value in an error + * message. We use two levels so that macros are resolved. + */ +#define _TOSTR(x) #x +#define TOSTR(x) _TOSTR(x) + +/* + * Gcc >= 3 provides the ability for the program to give hints to the + * compiler about what branch of an if is most likely to be taken. This + * helps the compiler produce the most compact critical paths, which is + * generally better for the cache and to reduce the number of jumps. + */ +#if !defined(likely) +#if !defined(__GNUC__) || (__GNUC__ < 3) +#define __builtin_expect(x,y) (x) +#define likely(x) (x) +#define unlikely(x) (x) +#else +#define likely(x) (__builtin_expect((x) != 0, 1)) +#define unlikely(x) (__builtin_expect((x) != 0, 0)) +#endif +#endif + +#ifndef __GNUC_PREREQ__ +#if defined(__GNUC__) && !defined(__INTEL_COMPILER) +#define __GNUC_PREREQ__(ma, mi) \ + (__GNUC__ > (ma) || __GNUC__ == (ma) && __GNUC_MINOR__ >= (mi)) +#else +#define __GNUC_PREREQ__(ma, mi) 0 +#endif +#endif + +#ifndef offsetof +#if __GNUC_PREREQ__(4, 1) +#define offsetof(type, field) __builtin_offsetof(type, field) +#else +#define offsetof(type, field) \ + ((size_t)(uintptr_t)((const volatile void *)&((type *)0)->field)) +#endif +#endif + +/* Linux-like "container_of". It returns a pointer to the structure of type + * <type> which has its member <name> stored at address <ptr>. + */ +#ifndef container_of +#define container_of(ptr, type, name) ((type *)(((void *)(ptr)) - ((long)&((type *)0)->name))) +#endif + +/* returns a pointer to the structure of type <type> which has its member <name> + * stored at address <ptr>, unless <ptr> is 0, in which case 0 is returned. + */ +#ifndef container_of_safe +#define container_of_safe(ptr, type, name) \ + ({ void *__p = (ptr); \ + __p ? (type *)(__p - ((long)&((type *)0)->name)) : (type *)0; \ + }) +#endif + + +/* From gcc 6 and above, enum values may have attributes */ +#if __GNUC_PREREQ__(6, 0) +#define ENUM_ATTRIBUTE(x) __attribute__(x) +#else +#define ENUM_ATTRIBUTE(x) +#endif + +/* Some architectures have a double-word CAS, sometimes even dual-8 bytes. + * Some architectures support unaligned accesses, others are fine with them + * but only for non-atomic operations. Also mention those supporting unaligned + * accesses and being little endian, and those where unaligned accesses are + * known to be fast (almost as fast as aligned ones). + */ +#if defined(__x86_64__) +#define HA_UNALIGNED +#define HA_UNALIGNED_LE +#define HA_UNALIGNED_LE64 +#define HA_UNALIGNED_FAST +#define HA_UNALIGNED_ATOMIC +#define HA_HAVE_CAS_DW +#define HA_CAS_IS_8B +#elif defined(__i386__) || defined(__i486__) || defined(__i586__) || defined(__i686__) +#define HA_UNALIGNED +#define HA_UNALIGNED_LE +#define HA_UNALIGNED_ATOMIC +#elif defined (__aarch64__) || defined(__ARM_ARCH_8A) +#define HA_UNALIGNED +#define HA_UNALIGNED_LE +#define HA_UNALIGNED_LE64 +#define HA_UNALIGNED_FAST +#define HA_HAVE_CAS_DW +#define HA_CAS_IS_8B +#elif defined(__arm__) && (defined(__ARM_ARCH_7__) || defined(__ARM_ARCH_7A__)) +#define HA_UNALIGNED +#define HA_UNALIGNED_LE +#define HA_UNALIGNED_FAST +#define HA_HAVE_CAS_DW +#endif + +/*********************** IMPORTANT NOTE ABOUT ALIGNMENT **********************\ + * Alignment works fine for variables. It also works on types and struct * + * members by propagating the alignment to the container struct itself, * + * but this requires that variables of the affected type are properly * + * aligned themselves. While regular variables will always abide, those * + * allocated using malloc() will not! Most platforms provide posix_memalign()* + * for this, but it's not available everywhere. As such one ought not to use * + * these alignment declarations inside structures that are dynamically * + * allocated. If the purpose is only to avoid false sharing of cache lines * + * for multi_threading, see THREAD_PAD() below. * +\*****************************************************************************/ + +/* sets alignment for current field or variable */ +#ifndef ALIGNED +#define ALIGNED(x) __attribute__((aligned(x))) +#endif + +/* sets alignment only on architectures preventing unaligned atomic accesses */ +#ifndef MAYBE_ALIGNED +#ifndef HA_UNALIGNED +#define MAYBE_ALIGNED(x) ALIGNED(x) +#else +#define MAYBE_ALIGNED(x) +#endif +#endif + +/* sets alignment only on architectures preventing unaligned atomic accesses */ +#ifndef ATOMIC_ALIGNED +#ifndef HA_UNALIGNED_ATOMIC +#define ATOMIC_ALIGNED(x) ALIGNED(x) +#else +#define ATOMIC_ALIGNED(x) +#endif +#endif + +/* sets alignment for current field or variable only when threads are enabled. + * Typically used to respect cache line alignment to avoid false sharing. + */ +#ifndef THREAD_ALIGNED +#ifdef USE_THREAD +#define THREAD_ALIGNED(x) __attribute__((aligned(x))) +#else +#define THREAD_ALIGNED(x) +#endif +#endif + +/* add a mandatory alignment for next fields in a structure */ +#ifndef ALWAYS_ALIGN +#define ALWAYS_ALIGN(x) union { } ALIGNED(x) +#endif + +/* add an optional alignment for next fields in a structure, only for archs + * which do not support unaligned accesses. + */ +#ifndef MAYBE_ALIGN +#ifndef HA_UNALIGNED +#define MAYBE_ALIGN(x) union { } ALIGNED(x) +#else +#define MAYBE_ALIGN(x) +#endif +#endif + +/* add an optional alignment for next fields in a structure, only for archs + * which do not support unaligned accesses for atomic operations. + */ +#ifndef ATOMIC_ALIGN +#ifndef HA_UNALIGNED_ATOMIC +#define ATOMIC_ALIGN(x) union { } ALIGNED(x) +#else +#define ATOMIC_ALIGN(x) +#endif +#endif + +/* add an optional alignment for next fields in a structure, only when threads + * are enabled. Typically used to respect cache line alignment to avoid false + * sharing. + */ +#ifndef THREAD_ALIGN +#ifdef USE_THREAD +#define THREAD_ALIGN(x) union { } ALIGNED(x) +#else +#define THREAD_ALIGN(x) +#endif +#endif + +/* add optional padding of the specified size between fields in a structure, + * only when threads are enabled. This is used to avoid false sharing of cache + * lines for dynamically allocated structures which cannot guarantee alignment. + */ +#ifndef THREAD_PAD +# ifdef USE_THREAD +# define __THREAD_PAD(x,l) char __pad_##l[x] +# define _THREAD_PAD(x,l) __THREAD_PAD(x, l) +# define THREAD_PAD(x) _THREAD_PAD(x, __LINE__) +# else +# define THREAD_PAD(x) +# endif +#endif + +/* The THREAD_LOCAL type attribute defines thread-local storage and is defined + * to __thread when threads are enabled or empty when disabled. + */ +#ifdef USE_THREAD +#define THREAD_LOCAL __thread +#else +#define THREAD_LOCAL +#endif + +/* The __decl_thread() statement is shows the argument when threads are enabled + * or hides it when disabled. The purpose is to condition the presence of some + * variables or struct members to the fact that threads are enabled, without + * having to enclose them inside a #ifdef USE_THREAD/#endif clause. + */ +#ifdef USE_THREAD +#define __decl_thread(decl) decl +#else +#define __decl_thread(decl) +#endif + +/* clang has a __has_feature() macro which reports true/false on a number of + * internally supported features. Let's make sure this macro is always defined + * and returns zero when not supported. + */ +#ifndef __has_feature +#define __has_feature(x) 0 +#endif + +#endif /* _HAPROXY_COMPILER_H */ |