[PATCH] Fortran: improve error recovery for EXTENDS_TYPE_OF() [PR106121]

[Harald Anlauf <anlauf@gmx.de>]

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Dear all,

the simplification of EXTENDS_TYPE_OF() did not handle the
situation that one of its arguments were a CLASS variable
that was improperly declared.  NULL pointer dereference.

The fix is obvious.  Steve found a similar solution, which
is why I added him as co-author.

Regtested on x86_64-pc-linux-gnu.

Will commit to mainline as obvious within 24 hours unless
there are loud objections.

Thanks,
Harald


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From 55aacfd22d73edfb38871e211f85b2ae69fd0072 Mon Sep 17 00:00:00 2001
From: Harald Anlauf <anlauf@gmx.de>
Date: Tue, 28 Jun 2022 22:29:28 +0200
Subject: [PATCH] Fortran: improve error recovery for EXTENDS_TYPE_OF()
 [PR106121]

gcc/fortran/ChangeLog:

	PR fortran/106121
	* simplify.cc (gfc_simplify_extends_type_of): Do not attempt to
	simplify when one of the arguments is a CLASS variable that was
	not properly declared.

gcc/testsuite/ChangeLog:

	PR fortran/106121
	* gfortran.dg/extends_type_of_4.f90: New test.

Co-authored-by: Steven G. Kargl <kargl@gcc.gnu.org>
---
 gcc/fortran/simplify.cc                       |  4 ++++
 .../gfortran.dg/extends_type_of_4.f90         | 20 +++++++++++++++++++
 2 files changed, 24 insertions(+)
 create mode 100644 gcc/testsuite/gfortran.dg/extends_type_of_4.f90

diff --git a/gcc/fortran/simplify.cc b/gcc/fortran/simplify.cc
index e8e3ec63669..ab59fbca622 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
diff --git a/gcc/testsuite/gfortran.dg/extends_type_of_4.f90 b/gcc/testsuite/gfortran.dg/extends_type_of_4.f90
new file mode 100644
index 00000000000..64373322387
--- /dev/null
+++ b/gcc/testsuite/gfortran.dg/extends_type_of_4.f90
@@ -0,0 +1,20 @@
+! { dg-do compile }
+! PR fortran/106121 - ICE in gfc_simplify_extends_type_of
+! Contributed by G.Steinmetz
+
+program p
+   type t
+   end type
+   type(t)  :: x
+   class(t) :: y               ! { dg-error "dummy, allocatable or pointer" }
+   print *, extends_type_of (x, y)
+end
+
+subroutine s
+   type t
+      integer :: i
+   end type
+   type(t)  :: x
+   class(t) :: y               ! { dg-error "dummy, allocatable or pointer" }
+   stop extends_type_of (x, y) ! { dg-error "STOP code" }
+end
--
2.35.3