Need help with debugging Segfault

[SomeDude]

On Sunday, 2 December 2012 at 04:45:13 UTC, 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

You have two pretty powerful tools to help you isolate and debug, 
they are not advertised enough imho:

1) DustMite a tool which allows to automatically reduce test 
cases. It has been used with success several times here.

2) (I haven't tried it yet, to tell the truth, but it DOES look 
pretty powerful. I'm really surprised noone seems interested, as 
it should allow one to reproduce a bug exactly, - even on another 
computer -, down to threading and GC issues), the tool (or rather 
I should say debugging environment) I mentionned here: 
http://forum.dlang.org/post/ymfxuozenafnsvuipnjr@forum.dlang.org 
(deterministic replay engine)

Maybe thses can help.