[Fortran, Patch] PR60334 - Segmentation fault on character pointer assignments

[Andre Vehreschild]

Hi Paul,

thanks for the reviewed and the valued comments. 

Just for completeness I have attached the patch with the changes requested.

Bootstraps and regtests ok on x86_64-linux-gnu.

Regards,
	Andre


On Mon, 12 Jan 2015 22:07:29 +0100
Paul Richard Thomas <paul.richard.thomas@gmail.com> wrote:

> Hi Andre,
> 
> +      if (INDIRECT_REF_P (parmse.string_length))
> +        /* In chains of functions/procedure calls the string_length already
> +           is a pointer to the variable holding the length.  Therefore
> +           remove the deref on call.  */
> +        parmse.string_length = TREE_OPERAND (parmse.string_length, 0);
> 
> This is OK but I would use instead:
> +      if (POINTER_TYPE_P (parmse.string_length))
> +        /* In chains of functions/procedure calls the string_length already
> +           is a pointer to the variable holding the length.  Therefore
> +           remove the deref on call.  */
> +        parmse.string_length = build_fold_indirect_ref
> (parmse.string_length);
> 
> If you look in ~/gcc/fold-const.c:15751, you will see that
> TREE_OPERAND (parmse.string_length, 0) but that it is preceded by
> cleaning up of NOOPS and, in any case, its usage will preserve the
> standard API.... just in case the internals change :-)
> 
> of course, using TREE_OPERAND (xxx, 0) in the various fortran class
> functions makes such an assumption ;-)
> 
> Apart from that, the patch is fine.
> 
> I'll have a session of doing some commits later this week and will do
> this patch at that time.
> 
> Cheers
> 
> Paul
> 
> On 11 January 2015 at 16:21, Andre Vehreschild <vehre@gmx.de> wrote:
> > Hi Paul,
> >
> > thanks for the review. I do not have commits rights.
> >
> > Unfortunately is the patch not ok. I figured today, that it needs an
> > extension when function calls that return deferred char len arrays are
> > nested. In this special case the string length would have been lost. The
> > attached extended version fixes this issue.
> >
> > Sorry for the duplicate work.
> >
> > Bootstraps and regtests ok on x86_64-linux-gnu.
> >
> > Regards,
> >         Andre
> >
> > On Sun, 11 Jan 2015 16:11:10 +0100
> > Paul Richard Thomas <paul.richard.thomas@gmail.com> wrote:
> >
> >> Dear Andre,
> >>
> >> This is OK for trunk. I have not been keeping track of whether or not
> >> you have commit rights yet. If not, I will get to it sometime this
> >> week.
> >>
> >> Thanks for the patch.
> >>
> >> Paul
> >>
> >> On 10 January 2015 at 15:59, Andre Vehreschild <vehre@gmx.de> wrote:
> >> > Hi all,
> >> >
> >> > attached patch fixes the bug reported in pr 60334. The issue here was
> >> > that the function's result being (a pointer to) a deferred length char
> >> > array. The string length for the result value was wrapped in a local
> >> > variable, whose value was never written back to the string length of the
> >> > result. This lead the calling routine to take the length of the result
> >> > to be random leading to a crash.
> >> >
> >> > This patch addresses the issue by preventing the instantiation of the
> >> > local var and instead using a reference to the parameter. This not only
> >> > saves one value on the stack, but also because for small functions the
> >> > compiler will hold all parameters in registers for a significant level
> >> > of optimization, all the overhead of memory access (I hope :-).
> >> >
> >> > Bootstraps and regtests ok on x86_64-linux-gnu.
> >> >
> >> > - Andre
> >> > --
> >> > Andre Vehreschild * Kreuzherrenstr. 8 * 52062 Aachen
> >> > Tel.: +49 241 9291018 * Email: vehre@gmx.de
> >>
> >>
> >>
> >
> >
> > --
> > Andre Vehreschild * Kreuzherrenstr. 8 * 52062 Aachen
> > Tel.: +49 241 9291018 * Email: vehre@gmx.de
> 
> 
> 


-- 
Andre Vehreschild * Kreuzherrenstr. 8 * 52062 Aachen
Tel.: +49 241 9291018 * Email: vehre@gmx.de 
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