[Bug fortran/77372] ICE in simplify_ieee_selected_real_kind, at fortran/simplify.c:7049

["kargl at gcc dot gnu.org" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=77372

--- Comment #2 from kargl at gcc dot gnu.org ---
Thous shalt dereference NULL pointers.

Index: simplify.c
===================================================================
--- simplify.c  (revision 239737)
+++ simplify.c  (working copy)
@@ -7044,9 +7044,19 @@ gfc_simplify_compiler_version (void)
 gfc_expr *
 simplify_ieee_selected_real_kind (gfc_expr *expr)
 {
-  gfc_actual_arglist *arg = expr->value.function.actual;
-  gfc_expr *p = arg->expr, *q = arg->next->expr,
-          *rdx = arg->next->next->expr;
+  gfc_actual_arglist *arg;
+  gfc_expr *p = NULL, *q = NULL, *rdx = NULL;
+
+  arg = expr->value.function.actual;
+  if (arg->expr)
+    p = arg->expr;
+  if (arg->next)
+    {
+      if (arg->next->expr)
+       q = arg->next->expr;
+      if (arg->next->next && arg->next->next->expr)
+       rdx = arg->next->next->expr;
+    }

   /* Currently, if IEEE is supported and this module is built, it means
      all our floating-point types conform to IEEE. Hence, we simply handle