/* * 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 /* * 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 #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 /* 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 /* silence the "unused" warnings without having to place painful #ifdefs. * For use with variables or functions. */ #define __maybe_unused __attribute__((unused)) /* 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. */ #if __GNUC__ >= 5 || (__GNUC__ == 4 && __GNUC_MINOR__ >= 5) #define my_unreachable() __builtin_unreachable() #else #define my_unreachable() #endif /* 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; }) /* * 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 /* 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 /* 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 /* 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 */