Need help with debugging Segfault

[Jonathan M Davis]

On Sunday, December 02, 2012 10:14:16 d coder wrote:
> Greetings
> 
> I have a code that crashes with current github dmd snapshot with a
> segfault. It compiles and runs fine with the released versions of DMD. I am
> using lots of structs and classes in the code and I believe the problem
> could be related with the other issues that are there with structs. When I
> give the compiled binary to valgrind, the report suggests that the segfault
> might be related to garbage collector. I wanted to isolate the issue and
> report it on bugzilla. Can somebody help me with the valgrind trace below
> here, and guide me where to look for the problem? My actual code is
> thousands of lines big and I am at a loss as to how I should isolate and
> report this issue.
> 
> Regards
> - Puneet
> 
> ==4453== Invalid read of size 8
> ==4453==    at 0x44EFF5: _D4nett5mule5Mule3esl6__dtorMFZv
> (../src/nett/mule.d:115)
> ==4453==    by 0x471124: _D4nett5mule5Mule9EslDomain11__fieldDtorMFZv
> (../src/nett/mule.d:7923)
> ==4453==    by 0x4AD845: rt_finalize2 (in
> /home/pgoel/mule/examples/test_code)
> ==4453==    by 0x4ABC92: _D2gc3gcx3Gcx11fullcollectMFZm (in
> /home/pgoel/mule/examples/test_code)
> ==4453==    by 0x4A9BBA: _D2gc3gcx2GC18fullCollectNoStackMFZv (in
> /home/pgoel/mule/examples/test_code)
> ==4453==    by 0x4A7F2C: gc_term (in /home/pgoel/mule/examples/test_code)
> ==4453==    by 0x48661B: _D2rt6dmain211_d_run_mainUiPPaPUAAaZiZi6runAllMFZv
> (in /home/pgoel/mule/examples/test_code)
> ==4453==    by 0x4860F5:
> _D2rt6dmain211_d_run_mainUiPPaPUAAaZiZi7tryExecMFMDFZvZv (in
> /home/pgoel/mule/examples/test_code)
> ==4453==    by 0x4860B1: _d_run_main (in
> /home/pgoel/mule/examples/test_code)
> ==4453==    by 0x485EF2: main (in /home/pgoel/mule/examples/test_code)
> ==4453==  Address 0x2c0 is not stack'd, malloc'd or (recently) free'd

Did you at least use gdb to figure out where the segfault is occuring? If you 
compile with -gc, then dmd should produce the proper debug symbols for gdb, 
allowing you to use gdb with D programmers (though support for things like 
strings isn't very good - then again, C++ support in gdb is pretty poor too). 
You need at least gdb 7.2 IIRC, but since the current version is something 
like 7.5, that probably won't be  problem.

- Jonathan M Davis