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[FFmpeg-devel] Fix missing used attribute for inline assembly variables

Message ID CALkRRgemcViHErA15hOThmTD9d2+qhbinN4_kACCvOBKXS8BYA@mail.gmail.com
State Superseded
Headers show

Commit Message

Thomas Köppe Oct. 30, 2017, 8:31 p.m. UTC 
Please find below the actual patch:
     #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
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Patch

==============

Variables used in inline assembly need to be marked with attribute((used)).
Static constants already were, via the define of DECLARE_ASM_CONST.
But DECLARE_ALIGNED does not add this attribute, and some of the variables
defined with it are const only used in inline assembly, and therefore
appeared dead.

This change makes FFMPEG linkable with Clang's ThinLTO.
---
 libavcodec/cabac.c | 2 +-
 libavutil/mem.h    | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/libavcodec/cabac.c b/libavcodec/cabac.c
index dd2b057c6d..7321b48901 100644
--- a/libavcodec/cabac.c
+++ b/libavcodec/cabac.c
@@ -32,7 +32,7 @@ 
 #include "cabac.h"
 #include "cabac_functions.h"

-const uint8_t ff_h264_cabac_tables[512 + 4*2*64 + 4*64 + 63] = {
+DECLARE_ALIGNED(1, const uint8_t, ff_h264_cabac_tables)[512 + 4*2*64 +
4*64 + 63] = {
     9,8,7,7,6,6,6,6,5,5,5,5,5,5,5,5,
     4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,
     3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,
diff --git a/libavutil/mem.h b/libavutil/mem.h
index 527cd03191..c4ee11af58 100644
--- a/libavutil/mem.h
+++ b/libavutil/mem.h
@@ -101,7 +101,7 @@ 
     #define DECLARE_ALIGNED(n,t,v)      t __attribute__ ((aligned
(FFMIN(n, 16)))) v
     #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_ALIGNED(n,t,v)      t av_used __attribute__ ((aligned
(n))) v