Analyzing a SEG FAULT that gdb doesn't help with

Jon TURNEY jon.turney@dronecode.org.uk
Thu Jul 30 14:40:00 GMT 2015


On 30/07/2015 00:16, Michael Enright wrote:
> So I tried to addr2line /usr/bin/cygwin1.dll 6155d363 and I got
> nothing (?? at ??:?) I then reviewed in setup-x86 the possible cygwin
> packages to see if there was a missing package I could use to enable
> cygwin1.dll's addresses to be translated but I didn't recognize
> anything.

You need to install the 'cygwin-debuginfo' package for debug symbols for 
cygwin1.dll

You also need to point addr2line at those detached debug symbols, as 
(unlike gdb) it doesn't follow .gnu_debuglink pointers.

(I'm assuming you've typoed 6155d363 here and it should be 0x6115D363 as 
the strace output says)

# addr2line -e /usr/lib/debug/usr/bin/cygwin1.dbg 0x6115D363
/usr/src/debug/cygwin-2.1.0-1/newlib/libc/machine/i386/strlen.S:64

> 1) Why is it not the case that gdb handles this SEGV in the usual
> manner? It too just allows the stackdump to be made and lets me know
> that the inferior has run its course.

This shouldn't happen.  Are you sure the crashing process is the direct 
inferior of gdb, and not some wrapper process which runs it? 
(uninstalled libtool generated binaries do this, for e.g.)



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