Bug #74565 for devel-nytprof: Insists on creating output file when loaded even with start=no

Tue Jan 31 10:04:48 2012 davidp [...] preshweb.co.uk - Ticket created

Subject:

Insists on creating output file when loaded even with start=no

I wanted to use Devel::NYTProf at runtime, enabling profiling only at certain points and controlling which file is written to. However, Devel::NYTProf insists on creating an output file when loading it, even if it's told not to start automatically, with e.g.: $ENV{NYTPROF} = "start:no"; require Devel::NYTProf; The workaround I had to use (in Dancer::Plugin::NYTProf) is to get a temporary filename via File::Temp and pass that to Devel::NYTProf, so it can create that file, then unlink the file straight afterwards (as it's not desired), then enable profiling to the the file it should actually write to at desired points at runtime with DB::enable_profile($filename). This works, but is obviously quite hackish. My expectation was that, if I'd told Devel::NYTProf *not* to start profiling until I manually started it, that it would not attempt to open a file for output until I told it to. It seems to me that it would make sense for opening an output file to be deferred until profiling is actually starting, to avoid this issue biting anyone else.

Tue Jan 31 17:33:49 2012 TIMB [...] cpan.org - Correspondence added

Try $ENV{NYTPROF} = "start=no"; :-)

Tue Jan 31 17:33:50 2012 The RT System itself - Status changed from 'new' to 'open'

Tue Jan 31 18:02:57 2012 davidp [...] preshweb.co.uk - Correspondence added

On 2012-01-31 22:33:49, TIMB wrote: Show quoted text

> Try $ENV{NYTPROF} = "start=no"; :-)

Oh, bugger, sorry - I made that typo initially, and NYTProf correctly blew up because it was an invalid option. I then fixed it to "start=no", but it still created a file. The exact (nasty, hackish) workaround I had to use was: my $tempfh = File::Temp->new; my $file = $tempfh->filename; $tempfh = undef; # let the file get deleted $ENV{NYTPROF} = "start=no:file=$file"; require Devel::NYTProf; unlink $file; When I used just $ENV{NYTPROF} = "start=no", it still created the file (or, rather, tried to; I was testing running a script in a dir to which I'd removed write access, as that was how the problem first showed up).

Tue Jan 31 18:38:39 2012 davidp [...] preshweb.co.uk - Correspondence added

Just to provide a more solid illustration: [davidp@supernova:~/tmp/nytproftest]$ ls -ld . dr-xr-xr-x 2 davidp davidp 4096 2012-01-31 23:37 . [davidp@supernova:~/tmp/nytproftest]$ cat testcase.pl #!/usr/bin/perl $ENV{NYTPROF} = "start=no"; require Devel::NYTProf; [davidp@supernova:~/tmp/nytproftest]$ perl testcase.pl NYTProf failed to open 'nytprof.out' for writing, error 13: Permission denied at /usr/local/lib/perl/5.10.0/Devel/NYTProf.pm line 45. Compilation failed in require at testcase.pl line 3.

Thu Feb 02 04:08:36 2012 TIMB [...] cpan.org - Correspondence added

Try this change to NYTProf.xs: - const char *mode = "wbx"; + const char *mode = (strnEQ(filename, "/dev/", 4) ? "wb" : "wbx"); and then use NYTPROF="start=no:file=/dev/null"

Thu Feb 02 04:08:37 2012 TIMB [...] cpan.org - Status changed from 'open' to 'patched'

Thu Feb 02 06:01:30 2012 davidp [...] preshweb.co.uk - Correspondence added

On 2012-02-02 09:08:36, TIMB wrote: Show quoted text

> Try this change to NYTProf.xs: > > - const char *mode = "wbx"; > + const char *mode = (strnEQ(filename, "/dev/", 4) ? "wb" : "wbx"); > > and then use NYTPROF="start=no:file=/dev/null"

I can confirm that the above change does indeed fix the problem for me - thanks! Personally, I'd check for /dev/null rather than just /dev/, though, in case someone is trying to tell Devel::NYTProf to write to e.g. /dev/shm to store the file temporarily in memory.

Thu Feb 02 06:01:32 2012 The RT System itself - Status changed from 'patched' to 'open'

Thu Feb 02 14:38:54 2012 Tim.Bunce [...] pobox.com - Correspondence added

Subject:	Re: [rt.cpan.org #74565] Insists on creating output file when loaded even with start=no
Date:	Thu, 2 Feb 2012 19:38:28 +0000
To:	David Precious via RT <bug-devel-nytprof [...] rt.cpan.org>
From:	Tim Bunce <Tim.Bunce [...] pobox.com>

Show quoted text

> I can confirm that the above change does indeed fix the problem for me - > thanks!

Great. Show quoted text

> Personally, I'd check for /dev/null rather than just /dev/, though, in > case someone is trying to tell Devel::NYTProf to write to e.g. /dev/shm > to store the file temporarily in memory.

Loosing the exclusive flag in such a case seems a minor loss compared to the gain of being able to write to other /dev's like /dev/fd/42 Tim.

Thu Feb 02 15:58:27 2012 TIMB [...] cpan.org - Correspondence added

Fixed in r2208. Thanks.

Thu Feb 02 15:58:28 2012 TIMB [...] cpan.org - Status changed from 'open' to 'resolved'

Bug #74565 for devel-nytprof: Insists on creating output file when loaded even with start=no

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