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List:       kde-bugs-dist
Subject:    [valgrind] [Bug 371966] No uninitialised values reported with PGI -Mstack_arrays
From:       Philippe Waroquiers <bugzilla_noreply () kde ! org>
Date:       2016-11-02 20:17:32
Message-ID: bug-371966-17878-Upuxo88Q3l () http ! bugs ! kde ! org/
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https://bugs.kde.org/show_bug.cgi?id=371966

Philippe Waroquiers <philippe.waroquiers@skynet.be> changed:

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--- Comment #2 from Philippe Waroquiers <philippe.waroquiers@skynet.be> ---
(In reply to Carl Ponder from comment #0)
> Created attachment 101954 [details]
> Simple Fortran test-case using array with dynamic bound.
> 
> I have a simple Fortran test-case that allocates an array and uses
> uninitialized values from it. Using the PGI compiler, if I compile it using
> the -Mstack_arrays option, valgrind reports 0 errors.
> 
> I also have a HUGE program (WRF) where valgrind is likewise not reporting
> anything in spite of the fact that uninitialized array-elements are being
> used, so I'm trying to track down issues like this one.
> 
> Can you guys explain what's going on? I'm also checking with PGI on this.
No idea, and when I try to reproduce on my debian box, it tells:
No command 'pgfortran' found, did you mean:
 Command 'gfortran' from package 'gfortran' (main)


So, here is what I suggest:
Compile your application with debugging information.

Then use gdb+vgdb to step in your application
(see
http://www.valgrind.org/docs/manual/manual-core-adv.html#manual-core-adv.gdbserver
for more information)

Use the xb monitor command: 
  xb <addr> [<len>] shows the definedness (V) bits and values for <len>
(default 1) bytes starting at <addr>
to see at which moment the memory of x(6..10) becomes initialised.
You probably better use --vgdb=full to be sure to step precisely (and even
maybe
use stepi when relevant).

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