From 33586ee770edaa036c27508b5ec5c8c263973941 Mon Sep 17 00:00:00 2001 From: Michael Niedermayer Date: Wed, 16 Jun 2010 04:53:09 +0000 Subject: Document FF_SYMVER and attribute_used Originally committed as revision 23622 to svn://svn.ffmpeg.org/ffmpeg/trunk --- libavutil/internal.h | 15 +++++++++++++++ 1 file changed, 15 insertions(+) (limited to 'libavutil/internal.h') diff --git a/libavutil/internal.h b/libavutil/internal.h index b361f722fa..08a34a6031 100644 --- a/libavutil/internal.h +++ b/libavutil/internal.h @@ -46,6 +46,12 @@ #endif #endif + +/** + * Marks a variable as used and prevents the compiler from optimizing it away. + * This is usefull for asm that accesses varibles in ways that the compiler doesnt + * understand + */ #ifndef attribute_used #if AV_GCC_VERSION_AT_LEAST(3,1) # define attribute_used __attribute__((used)) @@ -196,6 +202,15 @@ # define NULL_IF_CONFIG_SMALL(x) x #endif + +/** + * Create a non default alias for a function with specified version. + * This is needed when symbols are moved from a lib to a dependancy of the lib + * because the gnu linker as of 2010 is buggy and fails to dynamicaly link if a symbol + * is not found in the lib in which it was during link time with enabled versioning + * even if a correctly versioned and matching symbol exists in another lib and + * even if it did find that would it not contain an explicit check to fail + */ #if HAVE_SYMVER_ASM_LABEL # define FF_SYMVER(type, name, args, ver) \ type ff_##name args __asm__ (EXTERN_PREFIX #name "@" ver); \ -- cgit v1.2.3