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Introduce some allocation function attributes.

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Bring support for two gcc function attributes that are likely to be used
in our system headers:

__alloc_size
The alloc_size attribute is used to tell the compiler that the function
return value points to memory, where the size is given by one or two of
the functions parameters.

__result_use_check
Causes a warning to be emitted if a caller of the function with this
attribute does not use its return value. This is known in gcc as
"warn_unused_result" but we considered the original naming unsuitable
for an attribute.

The __alloc_size attribute required some workarounds for lint(1).
Both attributes are supported by clang.

Also see: D2107

MFC after:	3 days
This commit is contained in:
Pedro F. Giffuni 2015-03-26 16:00:35 +00:00
parent 4d9b9e1c9b
commit 8c2f8a839f
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=280700
1 changed files with 12 additions and 1 deletions
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13
sys/sys/cdefs.h
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@ -40,6 +40,9 @@
* Testing against Clang-specific extensions.
*/
#ifndef __has_attribute
#define __has_attribute(x) 0
#endif
#ifndef __has_extension
#define __has_extension __has_feature
#endif
@ -209,6 +212,7 @@
#define __unused
#define __packed
#define __aligned(x)
#define __alloc_size(...)
#define __section(x)
#define __weak
#else
@ -233,6 +237,11 @@
#define __aligned(x) __attribute__((__aligned__(x)))
#define __section(x) __attribute__((__section__(x)))
#endif
#if __has_attribute(alloc_size) || __GNUC_PREREQ__(4, 3)
#define __alloc_size(...) __attribute__((alloc_size(__VA_ARGS__)))
#else
#define __alloc_size(...)
#endif
#if defined(__INTEL_COMPILER)
#define __dead2 __attribute__((__noreturn__))
#define __pure2 __attribute__((__const__))
@ -242,7 +251,7 @@
#define __aligned(x) __attribute__((__aligned__(x)))
#define __section(x) __attribute__((__section__(x)))
#endif
#endif
#endif /* lint */
#if !__GNUC_PREREQ__(2, 95)
#define __alignof(x) __offsetof(struct { char __a; x __b; }, __b)
@ -363,8 +372,10 @@
#if __GNUC_PREREQ__(3, 4)
#define __fastcall __attribute__((__fastcall__))
#define __result_use_check __attribute__((__warn_unused_result__))
#else
#define __fastcall
#define __result_use_check
#endif
#if __GNUC_PREREQ__(4, 1)