Devel::TraceUse bizarreness

perl5ever has asked for the wisdom of the Perl Monks concerning the following question:

I'm using Devel::TraceUse with a script that uses the 'lib' module:

use lib 'my-lib';
use Fcntl;
[download]

Running perl -d:TraceUse script.pl results in:

Modules used from ./script.pl:
  lib, line 2 (0.003514)
    Fcntl, line 1 (0.000265)
      Fcntl, line 1 (0.000531)
        Fcntl, line 1 (0.000847)
          Fcntl, line 1 (0.001094)
  Fcntl, line 8 (0.001204)
    XSLoader, line 1 (1.7e-05)
    XSLoader, line 1 (0.000449)
    XSLoader, line 1 (0.000715)
    XSLoader, line 1 (0.000965)
    XSLoader, line 61 (0.001219)
[download]

If I add a for (@INC) { print "INC: $_\n" } after the use lib line, I get this output:

INC: my-lib/5.8.8/i386-linux-thread-multi
INC: my-lib/5.8.8
INC: my-lib/5.8.6
INC: my-lib
INC: CODE(0x98f8e08)
INC: ...(lots of other directories omitted)...
...
Modules used from ./script.pl:
  lib, line 2 (0.003122)
    Fcntl, line 1 (0.000253)
      Fcntl, line 1 (0.000494)
        Fcntl, line 1 (0.000747)
          Fcntl, line 1 (0.000995)
  Fcntl, line 8 (0.001262)
    XSLoader, line 1 (0.0002)
    XSLoader, line 1 (0.000423)
    XSLoader, line 1 (0.000659)
    XSLoader, line 1 (0.000736)
    XSLoader, line 61 (0.001646)
[download]

So it seems that when use lib adds multiple directories to @INC things go screwy for Devel::TraceUse.

I haven't run into this problem if use lib 'my-lib' only adds one directory to @INC.

Is there a way to fix this?

Comment on Devel::TraceUse bizarreness Select or Download Code

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Re: Devel::TraceUse bizarreness by ikegami (Patriarch) on Jul 05, 2009 at 18:14 UTC
I assume Devel:TraceUse is placing that code ref in `@INC`. If so, I'm guessing Devel::TraceUse needs to be loaded after all modifications to @INC have been made. If so, the first snippet below will exhibit the problem, but not the latter. `perl -d:TraceUse -Mlib=my-lib -e'use Fcntl'` [download] and `perl -Mlib=my-lib -d:TraceUse -e'use Fcntl'` [download] I can't verify this because the module fails its tests.	[reply] [d/l] [select]
Re: Devel::TraceUse bizarreness by perl5ever (Pilgrim) on Jul 06, 2009 at 15:45 UTC
Figured it out... Devel::TraceUse assumes it is the first module in the `@INC` list: `... { local *INC = [ @INC[ 1 .. $#INC ] ]; my $start_time = [ gettimeofday() ]; eval "package $package; require '$mod_name';"; $elapsed = tv_interval($start_time); } ...` [download] Another approach would be to tie `@INC` to an array implementation which always puts the coderef used by `Devel::TraceUse` at the beginning of the array. That is, regardless of whatever array operations you performed on `@INC`, `$INC[0]` would always return TraceUse's coderef. The real solution is to just redefine `require` if that's possible.	[reply] [d/l] [select]
Re: Devel::TraceUse bizarreness by Khen1950fx (Canon) on Jul 06, 2009 at 19:45 UTC
I couldn't replicate the problem, but I tried it using Find::Lib. `#!/usr/local/bin/perl use strict; use warnings; use Find::Lib 'my-lib'; use Fcntl qw(:DEFAULT :flock); for (@INC) { print "INC : $_\n" }` [download]	[reply] [d/l]