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On some operating systems, the error log contains a stack trace if mysqld dies unexpectedly. You can use this to find out where (and maybe why) mysqld died. See Section 5.2.2, “The Error Log”. To get a stack trace, you must not compile mysqld with the -fomit-frame-pointer option to gcc. See Section, “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 information
to find out where mysqld died. If you see no messages after
this, something went terribly wrong...

stack_bottom = 0x41fd0110 thread_stack 0x40000

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 information
to find out where mysqld died. If you see no messages after
this, something went terribly wrong...

stack_bottom = 0x41fd0110 thread_stack 0x40000

In the latter case, you can use the resolve_stack_dump utility to determine where mysqld died by using the following procedure:

  1. Copy the numbers from the stack trace to a file, for example mysqld.stack. The numbers should not include the surrounding square brackets:

  2. Make a symbol file for the mysqld server:

    shell> nm -n libexec/mysqld > /tmp/mysqld.sym

    If mysqld is not linked statically, use the following command instead:

    shell> nm -D -n libexec/mysqld > /tmp/mysqld.sym

    If you want to decode C++ symbols, use the --demangle, if available, to nm. If your version of nm does not have this option, you will need to use the c++filt command after the stack dump has been produced to demangle the C++ names.

  3. Execute the following command:

    shell> resolve_stack_dump -s /tmp/mysqld.sym -n mysqld.stack

    If you were not able to include demangled C++ names in your symbol file, process the resolve_stack_dump output using c++filt:

    shell> resolve_stack_dump -s /tmp/mysqld.sym -n mysqld.stack | c++filt

    This prints out where mysqld died. If that does not help you find out why mysqld died, you should create a bug report and include the output from the preceding command with the bug report.

    However, in most cases it does not help us to have just a stack trace to find the reason for the problem. To be able to locate the bug or provide a workaround, in most cases we need to know the statement that killed mysqld and preferably a test case so that we can repeat the problem! See Section 1.6, “How to Report Bugs or Problems”.

Newer versions of glibc stack trace functions also print the address as relative to the object. On glibc-based systems (Linux), the trace for a crash within a plugin looks something like:


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

shell> addr2line -fie 0x9a6

The addr2line utility is part of the binutils package on Linux.

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


To translate, use this command:

shell> gaddr2line -fie 0x1510

Windows already prints the address, function name and line:

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

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User Comments
  Posted by Martin Mokrejs on January 12, 2004
This is a nice way to resolve the stack trace:

echo "This scripts expects stack trace from your mysql error log file"
echo "placed in the current directory as ./stack"

if [ ! -r ./stack ]; then
echo "./stack file not present or readable"
exit 255

if [ -r /usr/local/mysql/bin/mysqld.sym.gz ]; then
gzip -dc /usr/local/mysql/bin/mysqld.sym.gz > ./symbols
echo "nm -n /usr/local/mysql/bin/mysqld > ./symbols"
nm -n /usr/local/mysql/bin/mysqld > ./symbols

echo "/usr/local/mysql/bin/resolve_stack_dump -s ./symbols -n ./stack"
/usr/local/mysql/bin/resolve_stack_dump -s ./symbols -n ./stack

# if you have c++ filter, use rather this output, it's even better
echo "if you don't have c++filter, the next command will fail"
echo "/usr/local/mysql/bin/resolve_stack_dump -s ./symbols -n ./stack | c++filter"
/usr/local/mysql/bin/resolve_stack_dump -s ./symbols -n ./stack | c++filter

  Posted by Martin Mokrejs on January 12, 2004
In my previous comment in the shellscript should be c++filt instead of c++filter. c++filt is a part of gcc package.
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