Diederick C. Niehorster: > FWIW, the macro > #define AV_MAKE_MAJOR_MINOR_FUNC_NAME(name,major,minor) > AV_GLUE(av,name)AV_GLUE(_version_,major)AV_GLUE(_,minor) > doesn't compile on patchwork > (https://patchwork.ffmpeg.org/check/49062/), but worked fine for me on > MSVC. Is MSVC non-compliant somehow? Suggestions appreciated, I'm no > star in C macros. >
AV_GLUE(av,name)AV_GLUE(_version_,major)AV_GLUE(_,minor) will yield three preprocessor tokens after macro expansion, one for each AV_GLUE. There will be no whitespace between them and yet they are different preprocessor tokens. After the preprocessor has been run, these preprocessor tokens are directly converted into tokens; there is no "rescan" that joins preprocessor tokens that are not separated by whitespace (and therefore appear to you to be a single token). And therefore the result is incompliant. It seems like MSVC does such a rescan, but the specs allow a compiler to omit it (and GCC apparently does so). > In any case, this is a discussion starter, so let it not compiling not > hold us back from that. > > Cheers, > Dee > > On Sun, Dec 26, 2021 at 6:17 PM Diederick Niehorster <dcni...@gmail.com> > wrote: >> >> As per discussion on the list ( >> https://ffmpeg.org/pipermail/ffmpeg-devel/2021-June/281513.html, see >> especially https://ffmpeg.org/pipermail/ffmpeg-devel/2021-June/281586.html), >> to resolve the the unholy ABI-relationship between libavdevice and >> libavformat and allow easier working on the part of the avdevice API >> that lives in avformat, lock avdevice to a specific major and minor >> version of avformat. >> >> Signed-off-by: Diederick Niehorster <dcni...@gmail.com> >> --- >> libavdevice/avdevice.c | 10 ++++++++++ >> libavdevice/version.h | 10 ++++++++++ >> libavformat/utils.c | 5 +++++ >> libavformat/version.h | 11 +++++++++++ >> libavutil/macros.h | 2 ++ >> 5 files changed, 38 insertions(+) >> >> diff --git a/libavdevice/avdevice.c b/libavdevice/avdevice.c >> index 8f460c7564..b608ec532f 100644 >> --- a/libavdevice/avdevice.c >> +++ b/libavdevice/avdevice.c >> @@ -38,6 +38,16 @@ unsigned avdevice_version(void) >> return LIBAVDEVICE_VERSION_INT; >> } >> >> +unsigned avdevice_version_same_minor() >> +{ >> + // check version of loaded lavf has same major and minor version as >> + // this library was compiled against >> + if ((avformat_version_same_minor()) & ~0xFF != (LIBAVFORMAT_VERSION_INT >> & ~0xFF)) >> + abort(); >> + >> + return avformat_version(); >> +} >> + >> const char * avdevice_configuration(void) >> { >> return FFMPEG_CONFIGURATION; >> diff --git a/libavdevice/version.h b/libavdevice/version.h >> index 41f568d6b0..4c511a7f53 100644 >> --- a/libavdevice/version.h >> +++ b/libavdevice/version.h >> @@ -26,6 +26,7 @@ >> */ >> >> #include "libavutil/version.h" >> +#include "libavutil/macros.h" >> >> #define LIBAVDEVICE_VERSION_MAJOR 59 >> #define LIBAVDEVICE_VERSION_MINOR 1 >> @@ -48,4 +49,13 @@ >> */ >> #define FF_API_DEVICE_CAPABILITIES (LIBAVDEVICE_VERSION_MAJOR < 60) >> >> +/** >> + * avdevice_version_same_minor() expands to a function with >> + * the same minor and major version it was compiled against >> + * encoded in it. Enables linking locking to the minor version >> + * of other libraries they were compiled against. >> + */ >> +#define avdevice_version_same_minor >> AV_MAKE_MAJOR_MINOR_FUNC_NAME(device,LIBAVFORMAT_VERSION_MAJOR,LIBAVFORMAT_VERSION_MINOR) >> +unsigned avdevice_version_same_minor(); >> + >> #endif /* AVDEVICE_VERSION_H */ >> diff --git a/libavformat/utils.c b/libavformat/utils.c >> index 332ba534d2..607a777c3f 100644 >> --- a/libavformat/utils.c >> +++ b/libavformat/utils.c >> @@ -63,6 +63,11 @@ unsigned avformat_version(void) >> return LIBAVFORMAT_VERSION_INT; >> } >> >> +unsigned avformat_version_same_minor() >> +{ >> + return avformat_version(); >> +} >> + >> const char *avformat_configuration(void) >> { >> return FFMPEG_CONFIGURATION; >> diff --git a/libavformat/version.h b/libavformat/version.h >> index 379a68cc7c..2423800687 100644 >> --- a/libavformat/version.h >> +++ b/libavformat/version.h >> @@ -28,6 +28,7 @@ >> */ >> >> #include "libavutil/version.h" >> +#include "libavutil/macros.h" >> >> // Major bumping may affect Ticket5467, 5421, 5451(compatibility with >> Chromium) >> // Also please add any ticket numbers that you believe might be affected >> here >> @@ -63,4 +64,14 @@ >> >> >> #define FF_API_R_FRAME_RATE 1 >> + >> +/** >> + * avformat_version_same_minor() expands to a function with >> + * the same minor and major version it was compiled against >> + * encoded in it. Enables linking locking to the minor version >> + * of other libraries they were compiled against. >> + */ >> +#define avformat_version_same_minor >> AV_MAKE_MAJOR_MINOR_FUNC_NAME(format,LIBAVFORMAT_VERSION_MAJOR,LIBAVFORMAT_VERSION_MINOR) >> +unsigned avformat_version_same_minor(); >> + >> #endif /* AVFORMAT_VERSION_H */ >> diff --git a/libavutil/macros.h b/libavutil/macros.h >> index 2a7567c3ea..dda1bf6452 100644 >> --- a/libavutil/macros.h >> +++ b/libavutil/macros.h >> @@ -73,6 +73,8 @@ >> * @} >> */ >> >> +#define AV_MAKE_MAJOR_MINOR_FUNC_NAME(name,major,minor) >> AV_GLUE(av,name)AV_GLUE(_version_,major)AV_GLUE(_,minor) >> + >> #define AV_PRAGMA(s) _Pragma(#s) >> >> #define FFALIGN(x, a) (((x)+(a)-1)&~((a)-1)) >> -- >> 2.28.0.windows.1 >> _______________________________________________ ffmpeg-devel mailing list ffmpeg-devel@ffmpeg.org https://ffmpeg.org/mailman/listinfo/ffmpeg-devel To unsubscribe, visit link above, or email ffmpeg-devel-requ...@ffmpeg.org with subject "unsubscribe".
