webRTC的github代码的更新速度还是很快的，研究webRTC的时候，不可避免的经常git pull去拿最新的代码。更新完之后，重新编译webRTC有时候会不成功，并且始终会失败在某一个文件的编译上。
1. 编译失败
更新完webRTC代码，开始编译，出现以下错误：
build stopped: subcommand failed
这个应该是ninja编译经常出现的一个error，但是根本原因还需要具体分析，我这边google了很长时间也没有找到solution.
2. 如何解决
（1）可以删掉代码库，重新clone一份，然后再编译。
这种方法可靠，但是不现实，因为非常费时间。除非真的想重新clone一份代码。
（2）打开编译log， 找到失败文件，单独产生目标文件
ninja -C out/Default -v
可以找到编译失败在哪一个文件，然后单独编译该文件，产生对应object file.
我在Debian系统下，不断的失败在webrtc_voice_engine_unittest.o：
FAILED: obj/media/rtc_media_unittests/webrtc_voice_engine_unittest.o
../../third_party/llvm-build/Release+Asserts/bin/clang++ -MMD -MF obj/media/rtc_media_unittests/webrtc_voice_engine_unittest.o.d -DWEBRTC_OPUS_SUPPORT_120MS_PTIME=1 -DUSE_UDEV -DUSE_AURA=1 -DUSE_GLIB=1 -DUSE_NSS_CERTS=1 -DUSE_X11=1 -D_FILE_OFFSET_BITS=64 -D_LARGEFILE_SOURCE -D_LARGEFILE64_SOURCE -D_GNU_SOURCE -DCR_CLANG_REVISION=\"n346557-4e0d9925-2\" -D__STDC_CONSTANT_MACROS -D__STDC_FORMAT_MACROS -D_LIBCPP_ABI_UNSTABLE -D_LIBCPP_DISABLE_VISIBILITY_ANNOTATIONS -D_LIBCXXABI_DISABLE_VISIBILITY_ANNOTATIONS -D_LIBCPP_ENABLE_NODISCARD -D_LIBCPP_DEBUG=0 -DCR_LIBCXX_REVISION=375504 -DCR_SYSROOT_HASH=79a7783607a69b6f439add567eb6fcb48877085c -D_DEBUG -DDYNAMIC_ANNOTATIONS_ENABLED=1 -DWEBRTC_ENABLE_PROTOBUF=1 -DWEBRTC_INCLUDE_INTERNAL_AUDIO_DEVICE -DRTC_ENABLE_VP9 -DHAVE_SCTP -DWEBRTC_NON_STATIC_TRACE_EVENT_HANDLERS=1 -DWEBRTC_POSIX -DWEBRTC_LINUX -DABSL_ALLOCATOR_NOTHROW=1 -DABSL_FLAGS_STRIP_NAMES=0 -DGTEST_API_= -DGTEST_HAS_POSIX_RE=0 -DGTEST_LANG_CXX11=1 -DGTEST_HAS_TR1_TUPLE=0 -DGTEST_HAS_ABSL=1 -DHAVE_WEBRTC_VIDEO -DUNIT_TEST -I../.. -Igen -I../../third_party/abseil-cpp -I../../third_party/libyuv/include -I../../third_party/googletest/custom -I../../third_party/googletest/src/googlemock/include -I../../third_party/googletest/custom -I../../third_party/googletest/src/googletest/include -fno-strict-aliasing --param=ssp-buffer-size=4 -fstack-protector -funwind-tables -fPIC -B../../third_party/binutils/Linux_x64/Release/bin -pthread -fcolor-diagnostics -fmerge-all-constants -fcrash-diagnostics-dir=../../tools/clang/crashreports -Xclang -mllvm -Xclang -instcombine-lower-dbg-declare=0 -fcomplete-member-pointers -m64 -march=x86-64 -Wno-builtin-macro-redefined -D__DATE__= -D__TIME__= -D__TIMESTAMP__= -Xclang -fdebug-compilation-dir -Xclang . -no-canonical-prefixes -Wall -Werror -Wextra -Wimplicit-fallthrough -Wunreachable-code -Wthread-safety -Wextra-semi -Wno-missing-field-initializers -Wno-unused-parameter -Wno-c++11-narrowing -Wno-unneeded-internal-declaration -Wno-undefined-var-template -Wno-ignored-pragma-optimize -Wno-implicit-int-float-conversion -Wno-final-dtor-non-final-class -Wno-builtin-assume-aligned-alignment -Wno-deprecated-copy -Wno-non-c-typedef-for-linkage -Wno-pointer-to-int-cast -O0 -fno-omit-frame-pointer -g2 -Xclang -debug-info-kind=constructor -gsplit-dwarf -ggnu-pubnames -ftrivial-auto-var-init=pattern -fvisibility=hidden -Wheader-hygiene -Wstring-conversion -Wtautological-overlap-compare -Wc++11-narrowing -Wimplicit-fallthrough -Wthread-safety -Winconsistent-missing-override -Wundef -Wunused-lambda-capture -Wno-shorten-64-to-32 -Wno-inconsistent-missing-override -Wno-undefined-bool-conversion -Wno-tautological-undefined-compare -std=c++14 -fno-exceptions -fno-rtti -nostdinc++ -isystem../../buildtools/third_party/libc++/trunk/include -isystem../../buildtools/third_party/libc++abi/trunk/include --sysroot=../../build/linux/debian_sid_amd64-sysroot -fvisibility-inlines-hidden -Wnon-virtual-dtor -Woverloaded-virtual -c ../../media/engine/webrtc_voice_engine_unittest.cc -o obj/media/rtc_media_unittests/webrtc_voice_engine_unittest.o
Killed
单独执行编译命令：
../../third_party/llvm-build/Release+Asserts/bin/clang++ -MMD -MF obj/media/rtc_media_unittests/webrtc_voice_engine_unittest.o.d -DWEBRTC_OPUS_SUPPORT_120MS_PTIME=1 -DUSE_UDEV -DUSE_AURA=1 -DUSE_GLIB=1 -DUSE_NSS_CERTS=1 -DUSE_X11=1 -D_FILE_OFFSET_BITS=64 -D_LARGEFILE_SOURCE -D_LARGEFILE64_SOURCE -D_GNU_SOURCE -DCR_CLANG_REVISION=\"n346557-4e0d9925-2\" -D__STDC_CONSTANT_MACROS -D__STDC_FORMAT_MACROS -D_LIBCPP_ABI_UNSTABLE -D_LIBCPP_DISABLE_VISIBILITY_ANNOTATIONS -D_LIBCXXABI_DISABLE_VISIBILITY_ANNOTATIONS -D_LIBCPP_ENABLE_NODISCARD -D_LIBCPP_DEBUG=0 -DCR_LIBCXX_REVISION=375504 -DCR_SYSROOT_HASH=79a7783607a69b6f439add567eb6fcb48877085c -D_DEBUG -DDYNAMIC_ANNOTATIONS_ENABLED=1 -DWEBRTC_ENABLE_PROTOBUF=1 -DWEBRTC_INCLUDE_INTERNAL_AUDIO_DEVICE -DRTC_ENABLE_VP9 -DHAVE_SCTP -DWEBRTC_NON_STATIC_TRACE_EVENT_HANDLERS=1 -DWEBRTC_POSIX -DWEBRTC_LINUX -DABSL_ALLOCATOR_NOTHROW=1 -DABSL_FLAGS_STRIP_NAMES=0 -DGTEST_API_= -DGTEST_HAS_POSIX_RE=0 -DGTEST_LANG_CXX11=1 -DGTEST_HAS_TR1_TUPLE=0 -DGTEST_HAS_ABSL=1 -DHAVE_WEBRTC_VIDEO -DUNIT_TEST -I../.. -Igen -I../../third_party/abseil-cpp -I../../third_party/libyuv/include -I../../third_party/googletest/custom -I../../third_party/googletest/src/googlemock/include -I../../third_party/googletest/custom -I../../third_party/googletest/src/googletest/include -fno-strict-aliasing --param=ssp-buffer-size=4 -fstack-protector -funwind-tables -fPIC -B../../third_party/binutils/Linux_x64/Release/bin -pthread -fcolor-diagnostics -fmerge-all-constants -fcrash-diagnostics-dir=../../tools/clang/crashreports -Xclang -mllvm -Xclang -instcombine-lower-dbg-declare=0 -fcomplete-member-pointers -m64 -march=x86-64 -Wno-builtin-macro-redefined -D__DATE__= -D__TIME__= -D__TIMESTAMP__= -Xclang -fdebug-compilation-dir -Xclang . -no-canonical-prefixes -Wall -Werror -Wextra -Wimplicit-fallthrough -Wunreachable-code -Wthread-safety -Wextra-semi -Wno-missing-field-initializers -Wno-unused-parameter -Wno-c++11-narrowing -Wno-unneeded-internal-declaration -Wno-undefined-var-template -Wno-ignored-pragma-optimize -Wno-implicit-int-float-conversion -Wno-final-dtor-non-final-class -Wno-builtin-assume-aligned-alignment -Wno-deprecated-copy -Wno-non-c-typedef-for-linkage -Wno-pointer-to-int-cast -O0 -fno-omit-frame-pointer -g2 -Xclang -debug-info-kind=constructor -gsplit-dwarf -ggnu-pubnames -ftrivial-auto-var-init=pattern -fvisibility=hidden -Wheader-hygiene -Wstring-conversion -Wtautological-overlap-compare -Wc++11-narrowing -Wimplicit-fallthrough -Wthread-safety -Winconsistent-missing-override -Wundef -Wunused-lambda-capture -Wno-shorten-64-to-32 -Wno-inconsistent-missing-override -Wno-undefined-bool-conversion -Wno-tautological-undefined-compare -std=c++14 -fno-exceptions -fno-rtti -nostdinc++ -isystem../../buildtools/third_party/libc++/trunk/include -isystem../../buildtools/third_party/libc++abi/trunk/include --sysroot=../../build/linux/debian_sid_amd64-sysroot -fvisibility-inlines-hidden -Wnon-virtual-dtor -Woverloaded-virtual -c ../../media/engine/webrtc_voice_engine_unittest.cc -o obj/media/rtc_media_unittests/webrtc_voice_engine_unittest.o
最后，再编译webRTC
ninja -C out/Default -v