[PATCH] Fortran: a C interoperable function cannot have the CLASS attribute [PR95375]

[Harald Anlauf <anlauf@gmx.de>]

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Dear all,

we obviously forgot to extend the C interoperability check of the
type of function results to CLASS variables and thus did not reject
them.  Wrong code could lead to an ICE, see testcase by Gerhard.

Regtested on x86_64-pc-linux-gnu.  OK for mainline?

Thanks,
Harald


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From dc22544c2412cf8810a4956f537a2f50e0711a05 Mon Sep 17 00:00:00 2001
From: Harald Anlauf <anlauf@gmx.de>
Date: Tue, 20 Dec 2022 21:17:08 +0100
Subject: [PATCH] Fortran: a C interoperable function cannot have the CLASS
 attribute [PR95375]

gcc/fortran/ChangeLog:

	PR fortran/95375
	* decl.cc (verify_bind_c_sym): Extend interoperability check to
	CLASS variables.

gcc/testsuite/ChangeLog:

	PR fortran/95375
	* gfortran.dg/bind_c_procs_4.f90: New test.
---
 gcc/fortran/decl.cc                          | 12 ++++++++----
 gcc/testsuite/gfortran.dg/bind_c_procs_4.f90 | 17 +++++++++++++++++
 2 files changed, 25 insertions(+), 4 deletions(-)
 create mode 100644 gcc/testsuite/gfortran.dg/bind_c_procs_4.f90

diff --git a/gcc/fortran/decl.cc b/gcc/fortran/decl.cc
index 1562dc22bc6..e593518a77e 100644
--- a/gcc/fortran/decl.cc
+++ b/gcc/fortran/decl.cc
@@ -5998,10 +5998,14 @@ verify_bind_c_sym (gfc_symbol *tmp_sym, gfc_typespec *ts,
 	    }
 	  else
 	    {
-              if (tmp_sym->ts.type == BT_DERIVED || ts->type == BT_DERIVED)
-                gfc_error ("Type declaration %qs at %L is not C "
-                           "interoperable but it is BIND(C)",
-                           tmp_sym->name, &(tmp_sym->declared_at));
+	      if (tmp_sym->ts.type == BT_DERIVED || ts->type == BT_DERIVED
+		  || tmp_sym->ts.type == BT_CLASS || ts->type == BT_CLASS)
+		{
+		  gfc_error ("Type declaration %qs at %L is not C "
+			     "interoperable but it is BIND(C)",
+			     tmp_sym->name, &(tmp_sym->declared_at));
+		  retval = false;
+		}
               else if (warn_c_binding_type)
                 gfc_warning (OPT_Wc_binding_type, "Variable %qs at %L "
                              "may not be a C interoperable "
diff --git a/gcc/testsuite/gfortran.dg/bind_c_procs_4.f90 b/gcc/testsuite/gfortran.dg/bind_c_procs_4.f90
new file mode 100644
index 00000000000..407d8bb9afc
--- /dev/null
+++ b/gcc/testsuite/gfortran.dg/bind_c_procs_4.f90
@@ -0,0 +1,17 @@
+! { dg-do compile }
+! PR fortran/95375 - ICE in add_use_op
+! Contributed by G.Steinmetz
+
+function f() result(n) bind(c)      ! { dg-error "not C interoperable" }
+  class(*), allocatable :: n
+end
+program p
+  interface
+     function f() result(n) bind(c)
+       integer :: n
+     end
+  end interface
+  if ( f() /= 0 ) stop
+end
+
+! { dg-prune-output "Type mismatch" }
--
2.35.3