[FFmpeg-devel] [PATCH v2] avcodec/libx264: allow to disable definition of X264_API_IMPORTS macro

[softworkz]

From: softworkz <softworkz at hotmail.com>

When MSVC is used, the definition of X264_API_IMPORTS is
required for shared linking to libx264.dll, but it must
not be defined in case of statically linking to libx264.

Defining DISABLE_X264_API_IMPORTS allows to disable the
definition of X264_API_IMPORTS for those cases.

This has become necessary due to:

https://code.videolan.org/videolan/x264/-/blob/
bfc87b7a330f75f5c9a21e56081e4b20344f139e/x264.h#L63-67

A better fix would eventually be this one:
http://ffmpeg.org/pipermail/ffmpeg-devel/2021-October/287426.html

But there has been disagreement and the issue stalled.

This patch is intended to be a stop-gap solution until
the mention fix will have been worked out.

Signed-off-by: softworkz <softworkz at hotmail.com>
---
    avcodec/libx264: don't define X264_API_IMPORTS when compiling static
    
    The definition of X264_API_IMPORTS is required for shared linking (when
    MSVC is used) but it must not be defined in case of static builds as is
    stated in x264.h:
    
    v2 use custom macro for control, so there's no mechanism imposed and no
    change as long as that macro isn't explicitly defined

Published-As: https://github.com/ffstaging/FFmpeg/releases/tag/pr-ffstaging-29%2Fsoftworkz%2Fsubmit_x264_api_imports-v2
Fetch-It-Via: git fetch https://github.com/ffstaging/FFmpeg pr-ffstaging-29/softworkz/submit_x264_api_imports-v2
Pull-Request: https://github.com/ffstaging/FFmpeg/pull/29

Range-diff vs v1:

 1:  640a17b84f ! 1:  bc86a3e903 avcodec/libx264: don't define X264_API_IMPORTS when compiling static
     @@ Metadata
      Author: softworkz <softworkz at hotmail.com>
      
       ## Commit message ##
     -    avcodec/libx264: don't define X264_API_IMPORTS when compiling static
     +    avcodec/libx264: allow to disable definition of X264_API_IMPORTS macro
      
     -    The definition of X264_API_IMPORTS is required for shared linking
     -    (when MSVC is used) but it must not be defined in case of static
     -    builds as is stated in x264.h:
     +    When MSVC is used, the definition of X264_API_IMPORTS is
     +    required for shared linking to libx264.dll, but it must
     +    not be defined in case of statically linking to libx264.
     +
     +    Defining DISABLE_X264_API_IMPORTS allows to disable the
     +    definition of X264_API_IMPORTS for those cases.
     +
     +    This has become necessary due to:
      
          https://code.videolan.org/videolan/x264/-/blob/
          bfc87b7a330f75f5c9a21e56081e4b20344f139e/x264.h#L63-67
      
     -    This commit adds a check for the definition of _LIB which indicates
     -    static linking.
     +    A better fix would eventually be this one:
     +    http://ffmpeg.org/pipermail/ffmpeg-devel/2021-October/287426.html
     +
     +    But there has been disagreement and the issue stalled.
     +
     +    This patch is intended to be a stop-gap solution until
     +    the mention fix will have been worked out.
      
          Signed-off-by: softworkz <softworkz at hotmail.com>
      
     @@ libavcodec/libx264.c
       #include "sei.h"
       
      -#if defined(_MSC_VER)
     -+#if defined(_MSC_VER) && !defined(_LIB)
     ++#if defined(_MSC_VER) && !defined(DISABLE_X264_API_IMPORTS)
       #define X264_API_IMPORTS 1
       #endif
       


 libavcodec/libx264.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/libavcodec/libx264.c b/libavcodec/libx264.c
index 4ce3791ae8..adeaf0f52f 100644
--- a/libavcodec/libx264.c
+++ b/libavcodec/libx264.c
@@ -37,7 +37,7 @@
 #include "atsc_a53.h"
 #include "sei.h"
 
-#if defined(_MSC_VER)
+#if defined(_MSC_VER) && !defined(DISABLE_X264_API_IMPORTS)
 #define X264_API_IMPORTS 1
 #endif
 

base-commit: 41a558fea06cc0a23b8d2d0dfb03ef6a25cf5100
-- 
ffmpeg-codebot