Changes between Version 14 and Version 15 of WebKitGTK/Debugging

Timestamp:

Jan 27, 2017, 10:04:12 AM (8 years ago)

Author:

clopez@igalia.com

Comment:

--

WebKitGTK/Debugging

@@ -17 +17 @@
 }}}
 
-In other to run ''GtkLauncher'' under ''gdb'' you should use a ''jhbuild'' shell and run ''gdb'' normally or use the ''jhbuild-wrapper'' as follows:
+If you want to debug the web process, the simplest way is to connect to it using gdb:
 {{{
-#!sh
-$ Tools/jhbuild/jhbuild-wrapper --gtk run gdb --args WebKitBuild/Debug/Programs/GtkLauncher
+$ gdb -p <pid of WebKitWebProcess>
 }}}
+However that doesn't work in all cases, because the web process might already have crashed when you are trying to connect to it.
+
+You can use the '''WEB_PROCESS_CMD_PREFIX''' environment variable (only works on Debug builds) for that purpose. If that variable is defined the web process will be run using its value as a prefix.
+
+Example:
+{{{
+WEB_PROCESS_CMD_PREFIX='/usr/bin/gdbserver localhost:8080' WebKitBuild/Debug/bin/MiniBrowser
+}}}
+and in a different terminal:
+{{{
+$ cd WebKitBuild/Debug
+$ gdb -q bin/WebKitWebProcess
+Reading symbols from bin/WebKitWebProcess...done.
+(gdb) target remote localhost:8080
+(gdb) continue
+}}}
+
+If you want to debug the network process you can use '''NETWORK_PROCESS_CMD_PREFIX''' in a similar way.
+
+Note that these variables are only enabled in debug builds. If you still want to use them in release builds you can remove the relevant
+'''#ifndef NDEBUG''' in '''ProcessLauncherGtk.cpp''',
+'''ProcessLauncher.h''', '''WebProcessProxyGtk.cpp''' and
+'''NetworkProcessProxySoup.cpp'''
+
+
+= Getting a backtrace =
+
+This works both with release and debug builds. If you are trying to get a backtrace from the WebKitGTK+ packages shipped by your distribution, '''ensure you have the corresponding dbgsym packages installed'''.
+
+* Open a terminal/shell, and enable coredumps
+{{{
+ulimit -c unlimited
+}}}
+* From that shell, run the browser and make it crash.
+* After it has crashed a file named "core" should have appeared on your working directory.
+  * If it wasn't the case ensure that you have not set the sysctl kernel.core_pattern set to another directory/pipe
+{{{
+$ sudo sysctl kernel.core_pattern=core
+}}}
+* Once you have the core, get a backtrace from it as follows:
+{{{
+gdb --batch -ex "thread apply all bt full" /full/path/to/WebKitWebProcess core &> backtrace.txt
+}}}
+  * If you get a [https://bugs.webkit.org/show_bug.cgi?id=159919 crash on the GDB demangler], you can workaround it as follows:
+    * Edit (or create) the file ${HOME}/.gdbinit 
+    * Write this line on it
+{{{
+set demangle-style none
+}}}
+    * And repeat the operation. You should not have got a backtrace with the files mangled.
+      * You can now manually demangle those symbols by piping the output as follows
+{{{
+cat backtrace.txt | c++filt
+}}}
+
+
+
+
+
 
 == Logging support ==
@@ -86 +144 @@
 }}}
 
-== Debugging WebKit2 ==
-
-If you want to debug the web process, the simplest way is to connect to
-it using gdb:
-{{{
-$ gdb -p <pid of WebKitWebProcess>
-}}}
-However that doesn't work in all cases, because the web process might
-already have crashed when you are trying to connect to it.
-
-You can use the '''WEB_PROCESS_CMD_PREFIX''' environment variable for
-that purpose. If that variable is defined the web process will be run
-using its value as a prefix.
-
-Example:
-{{{
-WEB_PROCESS_CMD_PREFIX='/usr/bin/gdbserver localhost:8080' WebKitBuild/Debug/bin/MiniBrowser
-}}}
-and in a different terminal:
-{{{
-$ cd WebKitBuild/Debug
-$ gdb -q bin/WebKitWebProcess
-Reading symbols from bin/WebKitWebProcess...done.
-(gdb) target remote localhost:8080
-(gdb) continue
-}}}
-
-If you want to debug the network process you can use
-'''NETWORK_PROCESS_CMD_PREFIX''' in a similar way.
-
-Note that these variables are only enabled in debug builds. If you
-still want to use them in release builds you can remove the relevant
-'''#ifndef NDEBUG''' in '''ProcessLauncherGtk.cpp''',
-'''ProcessLauncher.h''', '''WebProcessProxyGtk.cpp''' and
-'''NetworkProcessProxySoup.cpp'''
 
 == Debugging issues ==