re PR fortran/51338 (seg fault in gfc_dep_compare_expr with -O2)

2011-12-05  Thomas Koenig  <tkoenig@gcc.gnu.org>

	PR fortran/51338
	* dependency.c (are_identical_variables):  Handle case where
	end fields of substring references are NULL.

2011-12-05  Thomas Koenig  <tkoenig@gcc.gnu.org>

	PR fortran/51338
	* gfortran.dg/assumed_charlen_substring_1.f90:  New test.

From-SVN: r182024

gcc/fortran/ChangeLog

+2011-12-05  Thomas Koenig  <tkoenig@gcc.gnu.org>
+
+	PR fortran/51338
+	* dependency.c (are_identical_variables):  Handle case where
+	end fields of substring references are NULL.
+
 2011-12-04  Tobias Burnus  <burnus@net-b.de>
 
 	PR fortran/51383
@@ -12,7 +18,7 @@
 	* class.c (gfc_build_class_symbol): Handle
 	attr.select_type_temporary.
 
-2011-12-03  Tobias Burnus  <burnus@net-b.de>                                                                                                           
+2011-12-03  Tobias Burnus  <burnus@net-b.de>
 
 	PR fortran/50684
 	* check.c (variable_check): Fix intent(in) check.

gcc/fortran/dependency.c

@@ -173,9 +173,19 @@ are_identical_variables (gfc_expr *e1, gfc_expr *e2)
 	  break;
 
 	case REF_SUBSTRING:
-	  if (gfc_dep_compare_expr (r1->u.ss.start, r2->u.ss.start) != 0
-	      || gfc_dep_compare_expr (r1->u.ss.end, r2->u.ss.end) != 0)
+	  if (gfc_dep_compare_expr (r1->u.ss.start, r2->u.ss.start) != 0)
 	    return false;
+
+	  /* If both are NULL, the end length compares equal, because we
+	     are looking at the same variable. This can only happen for
+	     assumed- or deferred-length character arguments.  */ 
+
+	  if (r1->u.ss.end == NULL && r2->u.ss.end == NULL)
+	    break;
+
+	  if (gfc_dep_compare_expr (r1->u.ss.end, r2->u.ss.end) != 0)
+	    return false;
+	  
 	  break;
 
 	default:

gcc/testsuite/ChangeLog

+2011-12-05  Thomas Koenig  <tkoenig@gcc.gnu.org>
+
+	PR fortran/51338
+	* gfortran.dg/assumed_charlen_substring_1.f90:  New test.
+
 2011-12-05  Richard Sandiford  <rdsandiford@googlemail.com>
 
 	* g++.dg/debug/pr46338.C: Add dg-require-profiling.

gcc/testsuite/gfortran.dg/assumed_charlen_substring_1.f90

+! { dg-do compile }
+! { dg-options "-O -fdump-tree-original" }
+! PR 51338 - this used to ICE.
+! Original test case by Bud Davis.
+subroutine foo(a,b)
+  character(len=*) :: a
+  if (a(1:) /= a(1:)) call do_not_use
+end subroutine foo
+! { dg-final { scan-tree-dump-times "do_not_use" 0 "original" } }
+! { dg-final { cleanup-tree-dump "original" } }