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

[Tobias Burnus]

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 :-)


Regarding the patch, '!= IFSRC_IFBODY' has to be used; "== IFSRC_DECL"
won't work as the the generatedy ENTRY master function has IFSRC_UNKNOWN.

OK for mainline?

Tobias

PS: Some patch reviews are that fast that it is impossible to send the OK;
at least, I did not manage to do for Harald's last two - for the last one
I was at least 4min too late. ;-)

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