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On some operating systems, the error log contains a stack trace ifmysqld dies unexpectedly. You can use this to find out where (and maybe why)mysqld died. SeeSection 7.4.2, “The Error Log”. To get a stack trace, you must not compilemysqld with the-fomit-frame-pointer option to gcc. SeeSection 7.9.1.1, “Compiling MySQL for Debugging”.

A stack trace in the error log looks something like this:

mysqld got signal 11;Attempting backtrace. You can use the following informationto find out where mysqld died. If you see no messages afterthis, something went terribly wrong...stack_bottom = 0x41fd0110 thread_stack 0x40000mysqld(my_print_stacktrace+0x32)[0x9da402]mysqld(handle_segfault+0x28a)[0x6648e9]/lib/libpthread.so.0[0x7f1a5af000f0]/lib/libc.so.6(strcmp+0x2)[0x7f1a5a10f0f2]mysqld(_Z21check_change_passwordP3THDPKcS2_Pcj+0x7c)[0x7412cb]mysqld(_ZN16set_var_password5checkEP3THD+0xd0)[0x688354]mysqld(_Z17sql_set_variablesP3THDP4ListI12set_var_baseE+0x68)[0x688494]mysqld(_Z21mysql_execute_commandP3THD+0x41a0)[0x67a170]mysqld(_Z11mysql_parseP3THDPKcjPS2_+0x282)[0x67f0ad]mysqld(_Z16dispatch_command19enum_server_commandP3THDPcj+0xbb7[0x67fdf8]mysqld(_Z10do_commandP3THD+0x24d)[0x6811b6]mysqld(handle_one_connection+0x11c)[0x66e05e]

If resolution of function names for the trace fails, the trace contains less information:

mysqld got signal 11;Attempting backtrace. You can use the following informationto find out where mysqld died. If you see no messages afterthis, something went terribly wrong...stack_bottom = 0x41fd0110 thread_stack 0x40000[0x9da402][0x6648e9][0x7f1a5af000f0][0x7f1a5a10f0f2][0x7412cb][0x688354][0x688494][0x67a170][0x67f0ad][0x67fdf8][0x6811b6][0x66e05e]

Newer versions ofglibc stack trace functions also print the address as relative to the object. Onglibc-based systems (Linux), the trace for an unexpected exit within a plugin looks something like:

plugin/auth/auth_test_plugin.so(+0x9a6)[0x7ff4d11c29a6]

To translate the relative address (+0x9a6) into a file name and line number, use this command:

$> addr2line -fie auth_test_plugin.so 0x9a6auth_test_pluginmysql-trunk/plugin/auth/test_plugin.c:65

Theaddr2line utility is part of thebinutils package on Linux.

On Solaris, the procedure is similar. The Solarisprintstack() already prints relative addresses:

plugin/auth/auth_test_plugin.so:0x1510

To translate, use this command:

$> gaddr2line -fie auth_test_plugin.so 0x1510mysql-trunk/plugin/auth/test_plugin.c:88

Windows already prints the address, function name and line:

000007FEF07E10A4 auth_test_plugin.dll!auth_test_plugin()[test_plugin.c:72]