[Bug fortran/106121] ICE in gfc_simplify_extends_type_of, at fortran/simplify.cc:3109

[sgk at troutmask dot apl.washington.edu]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=106121

--- Comment #4 from Steve Kargl <sgk at troutmask dot apl.washington.edu> ---
On Tue, Jun 28, 2022 at 07:43:39PM +0000, anlauf at gcc dot gnu.org wrote:
> (In reply to kargl from comment #2)
> > Infamous NULL pointer dereference.
> 
> Yes.
> 
> Shorter fix:
> 
> diff --git a/gcc/fortran/simplify.cc b/gcc/fortran/simplify.cc
> index e8e3ec63669..b5112da441a 100644
> --- a/gcc/fortran/simplify.cc
> +++ b/gcc/fortran/simplify.cc
> @@ -3096,6 +3096,10 @@ gfc_simplify_extends_type_of (gfc_expr *a, gfc_expr
> *mold)
>    if (UNLIMITED_POLY (a) || UNLIMITED_POLY (mold))
>      return NULL;
> 
> +  if ((a->ts.type == BT_CLASS && !gfc_expr_attr (a).class_ok)
> +      || (mold->ts.type == BT_CLASS && !gfc_expr_attr (mold).class_ok))
> +    return NULL;
> +
>    /* Return .false. if the dynamic type can never be an extension.  */
>    if ((a->ts.type == BT_CLASS && mold->ts.type == BT_CLASS
>         && !gfc_type_is_extension_of
> 

Shorter is definitely better.  One thing that my patch
allowed was shortening the tortured if-statement that
is spread across a dozen of so lines.  In any event,
if you're patch survives regression testing, ok to
commit.