Re: gprof profiling of multi-threaded Cygwin programs

[Mark Geisert <mark at maxrnd dot com>]

On Thu, 18 Feb 2016, Jon Turney wrote:
> On 18/02/2016 11:29, Mark Geisert wrote:
> > > A brief search tells me that apparently glibc supports the
> > > (undocumented) GMON_OUT_PREFIX env var which enables a similar behaviour.
> >
> > Ah, I did not know about that.  It would be easy to implement.
> >
> > So I'm leaning towards choosing file name as GMON_OUT_PREFIX.exename.pid
> > with GMON_OUT_PREFIX defaulting to "gmon.out" if unspecified.
>
> I think if you are going to implement GMON_OUT_PREFIX, you should make the 
> behaviour the same as glibc.
>
> > Do you think the expanded name should be used in all cases, or only when
> > there's a gmon.out already present?
>
> I don't think you should be checking for an existing gmon.out file.  In the 
> simple case where the program doesn't fork, it's expected that gmon.out will 
> get overwritten.

OK, so the file name would be "gmon.out" if GMON_OUT_PREFIX is not 
specified, and $GMON_OUT_PREFIX.$pid if it is.  And don't check for 
existing files in either case.

I was also worried about a profiled program fork/exec'ing a different 
profiled program and so I considered having $exename be part of the 
file name.  But I now think following the undocumented glibc behavior is 
better in the long run.  One can arrange a different GMON_OUT_PREFIX for 
the execee if that's truly necessary.

Thanks; I appreciate the feedback.

..mark