Linux: make it possible to compile against libav when use_system_ffmpeg==1

media/media.gyp

Index: media/media.gyp
diff --git a/media/media.gyp b/media/media.gyp
index 0f836bcd969f519508d7ea396e3ae71f624d8970..b526beaa98915f1de6b7b233b0fc68745ff735d1 100644
--- a/media/media.gyp
+++ b/media/media.gyp
@@ -508,15 +508,27 @@
           ],
         }],
         ['use_system_ffmpeg == 1', {
-          'defines': [
+          'cflags': [

[DaleCurtis, 2013/04/15 23:12:53]

This section is pretty different than the previous. I don't understand your
changes here. Has compile_test changed in some way?

[Paweł Hajdan Jr., 2013/04/15 23:51:49]

defines -> cflags avoids a problem with gyp appending empty -D switches (may be
a change in gyp, may be a result of my test with more recent libraries)

__STDC_CONSTANT_MACROS is to avoid a spurious failure that happens when using
C++ compiler and makes the compile test always fail.

[DaleCurtis, 2013/04/16 20:46:56]

Can you put the #define and #include in a variable?

[Paweł Hajdan Jr., 2013/04/16 20:59:36]

I could technically, but unless you insist I'd prefer the current way.

The tests are supposed to be independent - any similarities between them are
accidental.

It is arguably easier to reason about them when you can see the whole program.

Otherwise - why not de-duplicate int main() { } in the same way? But IMO it
would actually decrease readability for no gain.

             '<!(python <(DEPTH)/tools/compile_test/compile_test.py '
-                '--code "#include <libavcodec/avcodec.h>\n'
+                '--code "#define __STDC_CONSTANT_MACROS\n'
+                '#include <libavcodec/avcodec.h>\n'
                 'int test() { return AV_CODEC_ID_OPUS; }" '
-                '--on-failure CHROMIUM_OMIT_AV_CODEC_ID_OPUS)',
+                '--on-failure -DCHROMIUM_OMIT_AV_CODEC_ID_OPUS=1)',
+
             '<!(python <(DEPTH)/tools/compile_test/compile_test.py '
-                '--code "#include <libavcodec/avcodec.h>\n'
+                '--code "#define __STDC_CONSTANT_MACROS\n'
+                '#include <libavcodec/avcodec.h>\n'
                 'int test() { return AV_CODEC_ID_VP9; }" '
-                '--on-failure CHROMIUM_OMIT_AV_CODEC_ID_VP9)',
+                '--on-failure -DCHROMIUM_OMIT_AV_CODEC_ID_VP9=1)',
+
+            '<!(python <(DEPTH)/tools/compile_test/compile_test.py '
+                '--code "#define __STDC_CONSTANT_MACROS\n'
+                '#include <libavcodec/avcodec.h>\n'
+                'int test() { struct AVFrame frame;\n'
+                'return av_frame_get_channels(&frame); }" '
+                '--on-failure '
+                '"\'-Dav_frame_get_channels(frame)=(av_get_channel_layout_nb_channels('
+                'frame->channel_layout))\'")',
           ],
         }],
         ['OS == "ios"', {