Hi Mikael,

Am 25.11.21 um 17:46 schrieb Mikael Morin:
Hello,

Le 24/11/2021 à 22:32, Harald Anlauf via Fortran a écrit :
diff --git a/gcc/fortran/check.c b/gcc/fortran/check.c
index 5a5aca10ebe..837eb0912c0 100644
--- a/gcc/fortran/check.c
+++ b/gcc/fortran/check.c
@@ -4866,10 +4868,17 @@ gfc_check_reshape (gfc_expr *source, gfc_expr
*shape,
     {
       gfc_constructor *c;
       bool test;
+      gfc_constructor_base b;

+      if (shape->expr_type == EXPR_ARRAY)
+        b = shape->value.constructor;
+      else if (shape->expr_type == EXPR_VARIABLE)
+        b = shape->symtree->n.sym->value->value.constructor;

This misses a check that shape->symtree->n.sym->value is an array, so
that it makes sense to access its constructor.

there are checks further above for the cases
  shape->expr_type == EXPR_ARRAY
and for
  shape->expr_type == EXPR_VARIABLE
which look at the elements of array shape to see if they are
non-negative.

Only in those cases where the full "if ()'s" pass we set
shape_is_const = true; and proceed.  The purpose of the auxiliary
bool shape_is_const is to avoid repeating the lengthy if's again.
Only then the above cited code segment should get executed.

For shape->expr_type == EXPR_ARRAY there is really no change in logic.
For shape->expr_type == EXPR_VARIABLE the above snipped is now executed,
but then we already had

  else if (shape->expr_type == EXPR_VARIABLE && shape->ref
           && shape->ref->u.ar.type == AR_FULL && shape->ref->u.ar.dimen == 1
           && shape->ref->u.ar.as
           && shape->ref->u.ar.as->lower[0]->expr_type == EXPR_CONSTANT
           && shape->ref->u.ar.as->lower[0]->ts.type == BT_INTEGER
           && shape->ref->u.ar.as->upper[0]->expr_type == EXPR_CONSTANT
           && shape->ref->u.ar.as->upper[0]->ts.type == BT_INTEGER
           && shape->symtree->n.sym->attr.flavor == FL_PARAMETER
           && shape->symtree->n.sym->value)

In which situations do I miss anything new?

Actually, this only supports the case where the parameter value is
defined by an array; but it could be an intrinsic call, a sum of
parameters, a reference to an other parameter, etc.

E.g. the following (still) does get rejected:

  print *, reshape([1,2,3,4,5], a+1)
  print *, reshape([1,2,3,4,5], a+a)
  print *, reshape([1,2,3,4,5], 2*a)
  print *, reshape([1,2,3,4,5], [3,3])
  print *, reshape([1,2,3,4,5], spread(3,dim=1,ncopies=2))

and has been rejected before.

The usual way to handle this is to call gfc_reduce_init_expr which (pray
for it) will make an array out of whatever the shape expression is.

Can you give an example where it fails?

I think the current code would almost certainly fail, too.

The rest looks good.
In the test, can you add a comment telling what it is testing?
Something like: "This tests that constant shape expressions passed to
the reshape intrinsic are properly simplified before being used to
diagnose invalid values"

Can do.

We also used to put a comment mentioning the person who submitted the
test, but not everybody seems to do it these days.

Can do.

Mikael


Harald

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