This is the last post on the instrumenting source code series. I hope you to find the tricks below as useful as the previous ones. <\/p>\n\n\n\n
In this post I show some more useful debugging tricks. Don’t forget to have a look at the other posts of the series:<\/p>\n\n\n\n
The source code shown below must be placed in the .h where the class to be debugged is defined. It’s written in a way that doesn’t need to rebuild Example output:<\/p>\n\n\n\n WebProcessMainGtk<\/a> and WebProcessMainWPE<\/a> will sleep for 30 seconds if a special environment variable is defined:<\/p>\n\n\n\n It only works In big pipelines (e.g. playbin) it can be very hard to find what element is replying to a query or handling an event. Even using gdb can be extremely tedious due to the very high level of recursion. My coworker Alicia<\/a> commented that using log tracers is more helpful in this case.<\/p>\n\n\n\n The names of the logging categories are somewhat inconsistent:<\/p>\n\n\n\n The log tracer code is in This is the last post on the instrumenting source code series. I hope you to find the tricks below as useful as the previous ones. In this post I show some more useful debugging tricks. Don’t forget to have a look at the other posts of the series: GStreamer WebKit debugging tricks using GDB (1\/2) … Continue reading GStreamer WebKit debugging by instrumenting source code (3\/3)<\/span><\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":[],"categories":[11,13,2,1,7,12],"tags":[20],"_links":{"self":[{"href":"https:\/\/eocanha.org\/blog\/wp-json\/wp\/v2\/posts\/584"}],"collection":[{"href":"https:\/\/eocanha.org\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/eocanha.org\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/eocanha.org\/blog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/eocanha.org\/blog\/wp-json\/wp\/v2\/comments?post=584"}],"version-history":[{"count":4,"href":"https:\/\/eocanha.org\/blog\/wp-json\/wp\/v2\/posts\/584\/revisions"}],"predecessor-version":[{"id":610,"href":"https:\/\/eocanha.org\/blog\/wp-json\/wp\/v2\/posts\/584\/revisions\/610"}],"wp:attachment":[{"href":"https:\/\/eocanha.org\/blog\/wp-json\/wp\/v2\/media?parent=584"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/eocanha.org\/blog\/wp-json\/wp\/v2\/categories?post=584"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/eocanha.org\/blog\/wp-json\/wp\/v2\/tags?post=584"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}RefCounted.h<\/code>, so it saves a lot of build time. It logs all refs, unrefs and adoptPtrs, so that any anomaly in the refcounting can be traced and investigated later. To use it, just make your class inherit from LoggedRefCounted<\/code> instead of RefCounted<\/code>.<\/p>\n\n\n\nvoid WTF::adopted(WTF::LoggedRefCounted<T>*) [with T = WebCore::MediaSourceClientGStreamerMSE]: this=0x673c07a4, refCount 1\nvoid WTF::adopted(WTF::LoggedRefCounted<T>*) [with T = WebCore::MediaSourceClientGStreamerMSE]: this=0x673c07a4, refCount 1\n^^^ Two adopts, this is not good.\nvoid WTF::LoggedRefCounted<T>::ref() [with T = WebCore::MediaSourceClientGStreamerMSE]: this=0x673c07a4, refCount 1 --> ...\nvoid WTF::LoggedRefCounted<T>::ref() [with T = WebCore::MediaSourceClientGStreamerMSE]: this=0x673c07a4, refCount ... --> 2\nvoid WTF::LoggedRefCounted<T>::deref() [with T = WebCore::MediaSourceClientGStreamerMSE]: this=0x673c07a4, refCount 2 --> ...\nvoid WTF::LoggedRefCounted<T>::deref() [with T = WebCore::MediaSourceClientGStreamerMSE]: this=0x673c07a4, refCount ... --> 1\nvoid WTF::adopted(WTF::LoggedRefCounted<T>*) [with T = WebCore::MediaSourceClientGStreamerMSE]: this=0x673c07a4, refCount 1\nvoid WTF::LoggedRefCounted<T>::deref() [with T = WebCore::MediaSourceClientGStreamerMSE]: this=0x673c07a4, refCount 1 --> ...\nvoid WTF::LoggedRefCounted<T>::deref() [with T = WebCore::MediaSourceClientGStreamerMSE]: this=0x673c07a4, refCount 1 --> ...\n^^^ Two recursive derefs, not good either.<\/pre>\n\n\n\n
#include \"Logging.h\"\n\nnamespace WTF {\n\ntemplate<typename T> class LoggedRefCounted : public WTF::RefCounted<T> {\n WTF_MAKE_NONCOPYABLE(LoggedRefCounted); WTF_MAKE_FAST_ALLOCATED;\npublic:\n void ref() {\n printf(\"%s: this=%p, refCount %d --> ...\\n\", __PRETTY_FUNCTION__, this, WTF::RefCounted<T>::refCount()); fflush(stdout);\n WTF::RefCounted<T>::ref();\n printf(\"%s: this=%p, refCount ... --> %d\\n\", __PRETTY_FUNCTION__, this, WTF::RefCounted<T>::refCount()); fflush(stdout);\n }\n\n void deref() {\n printf(\"%s: this=%p, refCount %d --> ...\\n\", __PRETTY_FUNCTION__, this, WTF::RefCounted<T>::refCount()); fflush(stdout);\n WTF::RefCounted<T>::deref();\n printf(\"%s: this=%p, refCount ... --> %d\\n\", __PRETTY_FUNCTION__, this, WTF::RefCounted<T>::refCount()); fflush(stdout);\n }\n\nprotected:\n LoggedRefCounted() { }\n ~LoggedRefCounted() { }\n};\n\ntemplate<typename T> inline void adopted(WTF::LoggedRefCounted<T>* object)\n{\n printf(\"%s: this=%p, refCount %d\\n\", __PRETTY_FUNCTION__, object, (object)?object->refCount():0); fflush(stdout);\n adopted(static_cast<RefCountedBase*>(object));\n}\n\n} \/\/ Namespace WTF<\/pre>\n\n\n\nPause WebProcess on launch<\/h2>\n\n\n\n
export WEBKIT2_PAUSE_WEB_PROCESS_ON_LAUNCH=1<\/pre>\n\n\n\n
#if ENABLE(DEVELOPER_MODE)<\/code>, so you might want to remove those ifdefs if you’re building in Release mode.<\/p>\n\n\n\nLog tracers<\/h2>\n\n\n\n
GST_TRACERS=log<\/code> enables additional GST_TRACE() calls all accross GStreamer. The following example logs entries and exits into the query function.<\/p>\n\n\n\nGST_TRACERS=log GST_DEBUG='query:TRACE'<\/pre>\n\n\n\n
subprojects\/gstreamer\/plugins\/tracers\/gstlog.c<\/code>.<\/p>\n","protected":false},"excerpt":{"rendered":"