Bail out in gfc_dep_compare_expr for a NULL argument.

2019-12-10  Martin Liska  <mliska@suse.cz>

	PR fortran/92874
	* dependency.c (gfc_dep_compare_expr): Bail out
	when one of the arguments is null.
2019-12-10  Martin Liska  <mliska@suse.cz>

	PR fortran/92874
	* gfortran.dg/pr92874.f90: New test.

From-SVN: r279181

gcc/fortran/ChangeLog

+2019-12-10  Martin Liska  <mliska@suse.cz>
+
+	PR fortran/92874
+	* dependency.c (gfc_dep_compare_expr): Bail out
+	when one of the arguments is null.
+
 2019-12-10  Thomas Koenig  <tkoenig@gcc.gnu.org>
 
 	PR fortran/92863

gcc/fortran/dependency.c

@@ -319,6 +319,8 @@ gfc_dep_compare_expr (gfc_expr *e1, gfc_expr *e2)
 
   if (e1 == NULL && e2 == NULL)
     return 0;
+  else if (e1 == NULL || e2 == NULL)
+    return -2;
 
   e1 = gfc_discard_nops (e1);
   e2 = gfc_discard_nops (e2);

gcc/testsuite/ChangeLog

+2019-12-10  Martin Liska  <mliska@suse.cz>
+
+	PR fortran/92874
+	* gfortran.dg/pr92874.f90: New test.
+
 2019-12-10  Thomas Koenig  <tkoenig@gcc.gnu.org>
 
 	PR fortran/92863

gcc/testsuite/gfortran.dg/pr92874.f90

+! { dg-do compile }
+! { dg-options "-O2" }
+! PR fortran/92874
+program p
+   call s('a')
+   call s('abc')
+end
+subroutine s(x)
+   character(*) :: x
+   print *, (x(1:1) == x(1:))
+end