tracing malloc/free call

Corinna Vinschen
Fri Jan 16 19:50:00 GMT 2015

On Jan 16 18:33, Marco Atzeri wrote:
> On 1/16/2015 5:22 PM, Corinna Vinschen wrote:
> >On Jan 16 16:44, Corinna Vinschen wrote:
> >>On Jan 16 15:23, Marco Atzeri wrote:
> >>>Attached patch that allows tracking of original caller,
> >>>for the 4 memory allocation calls.
> >>
> >>Thanks for the patch, but it won't work nicely either this way.  The
> >>problem is that, in theory, the code has to differ between internal and
> >>external callers.  Internal callers (that is, Cygwin functions itself)
> >>don't hop into the function via _sigfe/_sigbe.  Thus the output for
> >>internal callers of malloc/free is now wrong with your patch.
> I missed that point. ;-)
> First time I look at these inside details of cygwin

Hopefully not your last :)  Feel free to ask on the devs list if you
have questions about the code.

> >>The solution for this problem would be a test which checks if the return
> >>address is the _sigbe function and if so, returns *(_my_tls.stackptr-1),
> >>otherwise __builtin_return_address(0).  However, the symbol _sigbe is
> >>not exported since, so far, it was only used inside _sigfe.  This needs
> >>a bit of tweaking.  I'll have a look.
> >
> >I applied a patch to print the right caller address.  I created a new
> >macro caller_return_address() for reuse, should we have a desire to
> >print the caller address in other parts of the code.
> >
> >I'm going to create a snapshot with this change.  Please give it
> >a try.
> It works like charm.
> Much more easy to find misalignment between
> malloc/calloc/realloc and free calls

I'm glad it works for you, too.

Btw., did you see my PM?


Corinna Vinschen                  Please, send mails regarding Cygwin to
Cygwin Maintainer                 cygwin AT cygwin DOT com
Red Hat
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