Re: [Patch] Fortran: Avoid var initialization in interfaces [PR54753]

[Sandra Loosemore <sandra@codesourcery.com>]

On 9/29/21 2:53 AM, Tobias Burnus wrote:
> Found when looking at F2018:C839 / PR54753.
> 
> For INTENT(OUT) the dummy variable (might) also be default initialized
> or deallocated. However, with assumed rank, that causes issues, which
> C839 prevents. In the current GCC implementation, missing C839 constraint
> diagnostic, but also rejects-valid/ice-on-valid appears.
> 
> There are three issues, this patch solves the first:
> 
> * reject-valid issue due to adding the initializer also to a dummy
>    argument which is in an INTERFACE block. Having initializers in
>    INTERFACE blocks is pointless and causes for the attached testcase
>    the bogus error:
>    "Assumed-rank variable y at (1) may only be used as actual argument"
> 
> (Except for wasting resources and this error, they should be ignored
> in trans*.c and usually do not cause any further harm.)
> 
> 
> I think Sandra has a nearly ready patch to do the C839 constraint
> diagnostic, which needs the attached patch to do the checks.
> 
> The third issue is that GCC currently gives either an ICE or the
> above error message when declaring a procedure with a valid
> assumed-rank intent(out) dummy. This has still to be solved as well.
> But first I wanted to unblock Sandra's C839 work with this patch :-)

This has indeed allowed me to make progress on adding the diagnostic, 
but I'm seeing some test regressions on x86_64-linux-gnu that are due to 
this patch alone:

FAIL: gfortran.dg/default_initialization_3.f90   -O0  execution test
FAIL: gfortran.dg/default_initialization_3.f90   -O1  execution test
FAIL: gfortran.dg/default_initialization_3.f90   -O2  execution test
FAIL: gfortran.dg/default_initialization_3.f90   -O3 
-fomit-frame-pointer -funroll-loops -fpeel-loops -ftracer 
-finline-functions  execution test
FAIL: gfortran.dg/default_initialization_3.f90   -O3 -g  execution test
FAIL: gfortran.dg/default_initialization_3.f90   -Os  execution test

It is failing with STOP 5, so I guess it is over-eagerly removing 
initialization in something that is not an interface.

BTW, I think it would be better to open a new issue for this and the 
"third issue" you describe for this than to tag them with PR54753, since 
these initialization bugs aren't really related to the missing 
diagnostic in that issue except so far as the bogus error/crashes make 
it impossible to test for the missing diagnostic.  Personally, I find it 
really confusing to track which bugs have really been fixed when 
multiple bugs that need different fixes are lumped together in the same 
issue...  there might be patches committed for such a mashed-up issue, 
but which parts have been fixed and which not, and when is it safe to 
close the issue?  :-S

-Sandra