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Message-ID:	<55008C41.5060105@tiscali.co.uk>
Date:	Wed, 11 Mar 2015 18:41:05 +0000
From:	David Stacey <drstacey AT tiscali DOT co DOT uk>
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To:	cygwin AT cygwin DOT com
Subject:	Re: backtrace(3) in Cygwin?
References:	<550076EC DOT 40808 AT tiscali DOT co DOT uk> <20150311172244 DOT GL5732 AT calimero DOT vinschen DOT de>
In-Reply-To:	<20150311172244.GL5732@calimero.vinschen.de>
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On 11/03/15 17:22, Corinna Vinschen wrote:
> On Mar 11 17:10, David Stacey wrote:
>> Please could you tell me if Cygwin supports backtrace(3) and
>> backtrace_symbols(3) [1]? I can't find the execinfo.h header file, but
>> presumably Cygwin is capable of generating a backtrace because the 'bt'
>> command works in gdb.
> GDB's `bt' implementation has nothing to do with Cygwin's capability
> to walk a stack.  Cygwin only has limited capabilities there which
> are used to create the stackdump file, see the stack_walk class in
> exceptions.cc:
> https://sourceware.org/git/gitweb.cgi?p=newlib-cygwin.git;a=blob_plain;f=winsup/cygwin/exceptions.cc  
>
> If you want to create a backtrace(3) function set for Cygwin, feel
> free:https://cygwin.com/contrib.html
> I'm certainly not averse to patches...

Thanks for your reply. It shouldn't be too hard to create 
implementations of backtrace(3) and backtrace_symbols(3) using 
CaptureStackBackTrace() [1] and SymFromAddr() [2]. There should be 
enough information in a SYMBOL_INFO structure to create strings in the 
same format as backtrace_symbols().

backtrace_symbols_fd(3) might be harder, because I'm not sure I can 
honour the promise not to use heap memory internally. Also, note that 
the Windows functions mentioned above are single-threaded, and therefore 
any implementation based on them will be single-threaded also. Further, 
Windows XP is limited to 63 stack frames.

I'm rather busy at the moment, but if I have time then I'll have a go.

Dave.

[1] - 
https://msdn.microsoft.com/en-us/library/windows/desktop/bb204633%28v=vs.85%29.aspx
[2] - 
https://msdn.microsoft.com/en-us/library/windows/desktop/ms681323%28v=vs.85%29.aspx


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