https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107576
--- Comment #9 from anlauf at gcc dot gnu.org ---
Something like the following rejects NULL when there is no interface:
diff --git a/gcc/fortran/interface.cc b/gcc/fortran/interface.cc
index 49dbd1d886c..62b325b726d 100644
--- a/gcc/fortran/interface.cc
+++ b/gcc/fortran/interface.cc
@@ -4160,6 +4180,14 @@ gfc_procedure_use (gfc_symbol *sym, gfc_actual_arglist
**ap, locus *where)
return false;
}
+ if (a->expr && a->expr->expr_type == EXPR_NULL)
+ {
+ gfc_error ("Passing intrinsic NULL as actual argument at %L "
+ "requires an explicit interface", &a->expr->where);
+ a->expr->error = 1;
+ return false;
+ }
+
/* TS 29113, C407b. */
if (a->expr && a->expr->expr_type == EXPR_VARIABLE
&& symbol_rank (a->expr->symtree->n.sym) == -1)
