[Bug fortran/122206] abstract interface, passing arguments by value to C

[anlauf at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=122206

--- Comment #6 from anlauf at gcc dot gnu.org ---
Debugging the reduced testcase suggests that the interface gets clobbered
in gfc_get_formal_from_actual_arglist along a weird path.

Untested fix:

diff --git a/gcc/fortran/trans-types.cc b/gcc/fortran/trans-types.cc
index 26645b0f7f6..7e08ff1581c 100644
--- a/gcc/fortran/trans-types.cc
+++ b/gcc/fortran/trans-types.cc
@@ -3441,6 +3441,7 @@ gfc_get_function_type (gfc_symbol * sym,
gfc_actual_arglist *actual_args,
        }
     }
   if (sym->backend_decl == error_mark_node && actual_args != NULL
+      && sym->ts.interface == NULL
       && sym->formal == NULL && (sym->attr.proc == PROC_EXTERNAL
                                 || sym->attr.proc == PROC_UNKNOWN))
     gfc_get_formal_from_actual_arglist (sym, actual_args);