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linux-next/include/linux/compiler-gcc4.h
Linus Torvalds f9d1425007 Disallow gcc versions 4.1.{0,1}
These compiler versions are known to miscompile __weak functions and
thus generate kernels that don't necessarily work correctly.  If a weak
function is int he same compilation unit as a caller, gcc may end up
inlining it, and thus binding the weak function too early.

See

    http://gcc.gnu.org/bugzilla/show_bug.cgi?id=27781

for details.

Cc: Adrian Bunk <bunk@kernel.org>
Cc: Helge Deller <deller@gmx.de>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2009-01-02 09:29:43 -08:00

38 lines
1.3 KiB
C

#ifndef __LINUX_COMPILER_H
#error "Please don't include <linux/compiler-gcc4.h> directly, include <linux/compiler.h> instead."
#endif
/* GCC 4.1.[01] miscompiles __weak */
#if __GNUC_MINOR__ == 1 && __GNUC_PATCHLEVEL__ <= 1
# error Your version of gcc miscompiles the __weak directive
#endif
#define __used __attribute__((__used__))
#define __must_check __attribute__((warn_unused_result))
#define __compiler_offsetof(a,b) __builtin_offsetof(a,b)
#define __always_inline inline __attribute__((always_inline))
/*
* A trick to suppress uninitialized variable warning without generating any
* code
*/
#define uninitialized_var(x) x = x
#if __GNUC_MINOR__ >= 3
/* Mark functions as cold. gcc will assume any path leading to a call
to them will be unlikely. This means a lot of manual unlikely()s
are unnecessary now for any paths leading to the usual suspects
like BUG(), printk(), panic() etc. [but let's keep them for now for
older compilers]
Early snapshots of gcc 4.3 don't support this and we can't detect this
in the preprocessor, but we can live with this because they're unreleased.
Maketime probing would be overkill here.
gcc also has a __attribute__((__hot__)) to move hot functions into
a special section, but I don't see any sense in this right now in
the kernel context */
#define __cold __attribute__((__cold__))
#endif