Add VP8 and H264 depacketizer fuzzers.

webrtc/BUILD.gn

Index: webrtc/BUILD.gn
diff --git a/webrtc/BUILD.gn b/webrtc/BUILD.gn
index d12ade23082dce6801bbe3972c6d8e9504bca832..84d242c9c55fdccbedc6ac33114e7c48a0a75c7b 100644
--- a/webrtc/BUILD.gn
+++ b/webrtc/BUILD.gn
@@ -281,15 +281,12 @@ source_set("rtc_event_log") {
 }
 
 if (use_libfuzzer) {
-  group("webrtc_fuzzers") {
+  # This target is only here for gn to discover fuzzer build targets under

[pbos-webrtc, 2015/12/11 15:47:17]

Note that this is similar to what use_libfuzzer in src/BUILD.gn does under
Chromium. I don't think this group target is useful if we can't do wildcards
(test/fuzzers:*) because it'll get outdated and mismatch (also I don't think
anyone needs to build it).

[pbos-webrtc, 2015/12/11 15:54:30]

When getting this on the bots, we can run gn refs out/Release --all
--type=executable --as=output webrtc/test/fuzzers:webrtc_fuzzer_main to discover
them (that's what ClusterFuzz' upload bot does).

[kjellander_webrtc, 2015/12/14 07:11:37]

Is the goal here to have a minimum amount of objects to compile in order to get
the fuzz binaries for a bot building with use_libfuzzer=true?
Then I still suggest keeping the old name, so the CLI ends up being:
 out/Release --all
--type=executable --as=output webrtc:webrtc_fuzzers

[kjellander_webrtc, 2015/12/14 07:11:37]

If you create a target named 'fuzzers' (same as the directory name) inside
webrtc/test/fuzzers/BUILD.gn, it will be built by default if something depends
on 'webrtc/test/fuzzers'.
https://chromium.googlesource.com/chromium/src/+/master/tools/gn/docs/style_g...

Thus that gives you the possibility of maintaining a list of what should be
compiled in webrtc/fuzzers while keeping it simple for the above level including
it.

[pbos-webrtc, 2015/12/14 13:07:02]

The point is to not have such a list (because it requires duplication, and we've
already missed putting targets in this list). I need to have a link from webrtc
-> webrtc/test/fuzzers/BUILD.gn so that targets inside it can be built from gn
generated from root webrtc.

[kjellander_webrtc, 2015/12/14 18:49:06]

I read up a bit on the Chromium implementation and you're right, it uses gn refs
as a way to figure out which fuzzer executables exists, which is new to me (but
seems to work well).

However, I still think we should use my approach, with webrtc/BUILD.gn having a
target that builds all our fuzzer code. That needs to be a separate target as
'webrtc_tests' is already taken and is not built by Chromium (as we normally
don't want to build the test code in Chromium).

I think it should be 'webrtc_fuzzers', and it should build all our fuzzers. That
way, we can also set use_libfuzzer=true in our
https://chromium.googlesource.com/external/webrtc/+/master/build_overrides/we...
so they're built by default in our standalone build. Then we'll get protection
from compilation errors that otherwise would only be discovered during rolling
into WebRTC, since the code isn't compiled.
Even if we build all our fuzzers in 'webrtc_fuzzers', the 'gn refs' lookup will
still work for the Chromium bot.

+  # webrtc/test/fuzzers/.
+  group("webrtc_fuzzer_gn_link") {

[kjellander_webrtc, 2015/12/14 07:11:37]

I prefer the old name, I don't like the _gn_link suffix

[pbos-webrtc, 2015/12/14 13:07:02]

Point was to point out that it's not a "real" target, so that no one tries to
build it. I've changed it to "webrtc_fuzzers_dummy", because building this
target doesn't give you any fuzzers.

[kjellander_webrtc, 2015/12/14 18:49:06]

I think it would be useful to have a target we can build, otherwise the code
will stop compiling as soon someone commits a mistake, or some new Clang
compilation warning is rolled in without the code being actually compiled for
every build.

     testonly = true
     deps = [
-      "test/fuzzers:audio_decoder_ilbc_fuzzer",
-      "test/fuzzers:audio_decoder_isac_fuzzer",
-      "test/fuzzers:audio_decoder_isacfix_fuzzer",
-      "test/fuzzers:audio_decoder_opus_fuzzer",
-      "test/fuzzers:vp8_qp_parser_fuzzer",
-      "test/fuzzers:vp9_depacketizer_fuzzer",
+      "test/fuzzers:webrtc_fuzzer_main",
     ]
   }
 }