@@ -100,6 +100,12 @@
* @param v Name of the variable
*/
+#if defined(__GNUC__) && !(defined(_WIN32) || defined(__CYGWIN__))
+ #define av_visibility_hidden __attribute__ ((visibility ("hidden")))
+#else
+ #define av_visibility_hidden
+#endif
+
#if defined(__INTEL_COMPILER) && __INTEL_COMPILER < 1110 || defined(__SUNPRO_C)
#define DECLARE_ALIGNED(n,t,v) t __attribute__ ((aligned (n))) v
#define DECLARE_ASM_ALIGNED(n,t,v) t __attribute__ ((aligned (n))) v
@@ -110,7 +116,7 @@
#define DECLARE_ASM_CONST(n,t,v) static const t av_used __attribute__ ((aligned (FFMIN(n, 16)))) v
#elif defined(__GNUC__) || defined(__clang__)
#define DECLARE_ALIGNED(n,t,v) t __attribute__ ((aligned (n))) v
- #define DECLARE_ASM_ALIGNED(n,t,v) t av_used __attribute__ ((aligned (n))) v
+ #define DECLARE_ASM_ALIGNED(n,t,v) t av_used __attribute__ ((aligned (n))) av_visibility_hidden v
#define DECLARE_ASM_CONST(n,t,v) static const t av_used __attribute__ ((aligned (n))) v
#elif defined(_MSC_VER)
#define DECLARE_ALIGNED(n,t,v) __declspec(align(n)) t v
Inline asm code assumes these DECLARE_ASM_ALIGNED declared global constants are non-preemptive, e.g. libavcodec/x86/cabac.h "lea "MANGLE(ff_h264_cabac_tables)", %0 \n\t" These constants are currently defined in C files with default visibility. Such object files require either -Wl,-Bsymbolic or -Wl,--version-script,libavcodec/libavcodec.ver to link into a shared object. However, there are good reasons that the user wants to specify neither option: * -Bsymbolic is dangerous as it breaks C++ semantics about address uniqueness of inline functions, type_info, ... * --version-script applies to all exported symbols and can thus affect program code. If the program code doesn't want all of its symbols to be marked local, it needs to define its own version script combining FFmpeg's version scripts. This is cumbersome. If neither -Bsymbolic nor --version-script is specified, there will be linker errors like: ld.lld: error: relocation R_X86_64_PC32 cannot be used against symbol ff_h264_cabac_tables; recompile with -fPIC It is better to express the intention explicitly and mark such global constants hidden. This patch marks a large number of such constants (accessible from assembly) hidden. Signed-off-by: Fangrui Song <maskray@google.com> --- Changes in v2: * Rewrote description * Used av_ prefixed av_visibility_hidden * The patch is a re-send of http://ffmpeg.org/pipermail/ffmpeg-devel/2019-March/241054.html --- libavutil/mem.h | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-)