include/common/compiler.h - haproxy - Gitiles

 /*
  * include/common/compiler.h
  * This files contains some compiler-specific settings.
  *
  * Copyright (C) 2000-2009 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 _COMMON_COMPILER_H
 #define _COMMON_COMPILER_H


 /*
  * Gcc before 3.0 needs [0] to declare a variable-size array
  */
 #ifndef VAR_ARRAY
 #if  __GNUC__  < 3
 #define VAR_ARRAY	0
 #else
 #define VAR_ARRAY
 #endif
 #endif


 /* By default, gcc does not inline large chunks of code, but we want it to
  * respect our choices.
  */
 #if !defined(forceinline)
 #if __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 __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

 /* 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

 #endif /* _COMMON_COMPILER_H */
	/*
	* include/common/compiler.h
	* This files contains some compiler-specific settings.
	*
	* Copyright (C) 2000-2009 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 _COMMON_COMPILER_H
	#define _COMMON_COMPILER_H


	/*
	* Gcc before 3.0 needs [0] to declare a variable-size array
	*/
	#ifndef VAR_ARRAY
	#if __GNUC__ < 3
	#define VAR_ARRAY 0
	#else
	#define VAR_ARRAY
	#endif
	#endif


	/* By default, gcc does not inline large chunks of code, but we want it to
	* respect our choices.
	*/
	#if !defined(forceinline)
	#if __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 __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

	/* 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

	#endif /* _COMMON_COMPILER_H */