Debugging low level problems with Valgrind

["Alex Bennée" <kernel-hacker@bennee.com>]

Hi,

I'm currently trying to track down the rather annoying --daemon crash
when I delete-frame (reported on list). As it's a access after free I
thought I would try using valgrind to find where the free occurs (it's
also sporadic, it doesn't happen every delete frame).

So far I've had no joy getting valgrind to run. I've built with

CFLAGS="-O0 0g3" ./configure --with-x-toolkit=lucid

But valgrind keeps complaining when I run:

--17777-- Contents of /proc/version:
--17777--   Linux version 3.8.11 (chrome-bot@build31-m2) (gcc version 4.8.x-google 20130905 (prerelease) (4.8.1_cos_gg_b42cc22_4.8.1-r62) ) #1 SMP Thu Jan 23 19:39:17 PST 2014
--17777-- Arch and hwcaps: AMD64, amd64-cx16-rdtscp-sse3-avx
--17777-- Page sizes: currently 4096, max supported 4096
--17777-- Valgrind library directory: /usr/lib/valgrind
--17777-- Reading syms from /home/alex/src/emacs/emacs.git/src/emacs
--17777-- WARNING: Serious error when reading debug info
--17777-- When reading debug info from /home/alex/src/emacs/emacs.git/src/emacs:
--17777-- Can't make sense of .data section mapping

And then later on is finding stuff but can't resolv the symbols:

==17803== Invalid free() / delete / delete[] / realloc()
==17803==    at 0x4C2C72E: realloc (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
==17803==    by 0x5A840B: ??? (in /home/alex/src/emacs/emacs.git/src/emacs)
==17803==    by 0x59ED7A: ??? (in /home/alex/src/emacs/emacs.git/src/emacs)
==17803==    by 0x5A748C: ??? (in /home/alex/src/emacs/emacs.git/src/emacs)
==17803==    by 0x58D045: ??? (in /home/alex/src/emacs/emacs.git/src/emacs)
==17803==    by 0x58D30A: ??? (in /home/alex/src/emacs/emacs.git/src/emacs)
==17803==    by 0x58DD14: ??? (in /home/alex/src/emacs/emacs.git/src/emacs)
==17803==    by 0x5F6B9A: ??? (in /home/alex/src/emacs/emacs.git/src/emacs)
==17803==    by 0x5F72C9: ??? (in /home/alex/src/emacs/emacs.git/src/emacs)
==17803==    by 0x5CEF1F: ??? (in /home/alex/src/emacs/emacs.git/src/emacs)
==17803==    by 0x610E8B: ??? (in /home/alex/src/emacs/emacs.git/src/emacs)
==17803==    by 0x5CF53E: ??? (in /home/alex/src/emacs/emacs.git/src/emacs)
==17803==  Address 0x1014070 is not stack'd, malloc'd or (recently) free'd

I'm wondering if I have a subtly busted toolchain or there are some
other magic runes I should use to set emacs up for valgrinding.

-- 
Alex Bennée