[Patch, fortran] PR66079 - [6 Regression] memory leak with source allocation in internal subprogram

[Paul Richard Thomas]

Dear Andre,

To answer your fist question - no, it doesn't. I was working with my
laptop, which is over slow when it comes to
updating. I should have realised that since you are working in this
area that there might be a problem. I discovered it when I did an
update on my workstation this afternoon. Of course the fixes are
trivial.

As to your second question about the chunk that avoids creating an
expr3. Yes, I am aware of the consequences. I am perfectly happy to
insert a TODO that saying that we should effect all the good things
that happen when the standard assignment is used in another block of
code. Alternatively, we could make a temporary variable to which the
expr3 is assigned that is used latter in the assignment to the
allocated variables.  For the moment though, repeating evaluation of
expressions seems like a small price to pay for avoiding memory
leakage.

Cheers

Paul



On 23 May 2015 at 19:52, Andre Vehreschild <vehre@gmx.de> wrote:
> Hi Paul,
>
> does this patch apply to current trunk cleanly? I get an issue with the last
> hunk, because all of the prerequisites are gone since r223445. The string copy
> is completely handled by the trans_assignment at the bottom of the if
> (code->expr3) block. Therefore I doubt the patches last hunk is needed any
> longer.
>
> Do you have an example why this hunk is needed?
>
> Index: gcc/fortran/trans-stmt.c
> ===================================================================
> *** gcc/fortran/trans-stmt.c    (revision 223233)
> --- gcc/fortran/trans-stmt.c    (working copy)
> *************** gfc_trans_allocate (gfc_code * code)
> *** 5200,5206 ****
>                 }
>               /* else expr3 = NULL_TREE set above.  */
>             }
> !         else
>             {
>               /* In all other cases evaluate the expr3 and create a
>                  temporary.  */
> --- 5200,5207 ----
>                 }
>               /* else expr3 = NULL_TREE set above.  */
>             }
> !         else if (!(code->expr3->ts.type == BT_DERIVED
> !                    && code->expr3->ts.u.derived->attr.alloc_comp))
>             {
>               /* In all other cases evaluate the expr3 and create a
>                  temporary.  */
>
> When I get the code right, than all derived-typed source= expressions that have
> an allocatable component will not be prepared for copy to the allocated object.
> This also means, that functions returning an object of such a type are called
> multiple times. Once for each object to allocate. Is this really desired?
>
> I am sorry, that I have to say that, but the check2305.diff file does not bring
> the testcase with it.
>
> Regards,
>         Andre
>
>
> On Sat, 23 May 2015 14:48:53 +0200
> Paul Richard Thomas <paul.richard.thomas@gmail.com> wrote:
>
>> Dear All,
>>
>> This patch started out fixing a single source of memory leak and then
>> went on to fix various other issues that I found upon investigation.
>>
>> The fortran ChangeLog entry is sufficiently descripive that I do not
>> think that there is a need to say more.
>>
>> Bootstrapped and regtested on x86_64/FC21 - OK for trunk?
>>
>> I am rather sure that some of the issues go further back than 6.0. I
>> will investigate what should be fixed for 5.2.
>>
>> Cheers
>>
>> Paul
>>
>> 2015-05-23  Paul Thomas  <pault@gcc.gnu.org>
>>
>>     PR fortran/66079
>>     * trans-expr.c (gfc_conv_procedure_call): Allocatable scalar
>>     function results must be freed and nullified after use. Create
>>     a temporary to hold the result to prevent duplicate calls.
>>     * trans-stmt.c (gfc_trans_allocate): Prevent memory leaks by
>>     not evaluating expr3 for scalar derived types with allocatable
>>     components. Fixed character length allocatable results and
>>     dummies need to be dereferenced. Also, if al_len is NULL use
>>     memsz for the string copy.
>>
>> 2015-05-23  Paul Thomas  <pault@gcc.gnu.org>
>>
>>     PR fortran/66079
>>     * gfortran.dg/allocatable_scalar_13.f90: New test
>
>
> --
> Andre Vehreschild * Email: vehre ad gmx dot de



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