re PR c++/56582 (ICE on negative array index in C++11 constant expression evaluation)

/cp
2013-03-16  Paolo Carlini  <paolo.carlini@oracle.com>

	PR c++/56582
	* semantics.c (cxx_eval_array_reference): Check for negative index.

/testsuite
2013-03-16  Paolo Carlini  <paolo.carlini@oracle.com>

	PR c++/56582
	* g++.dg/cpp0x/constexpr-array5.C: New.

From-SVN: r196701

gcc/cp/ChangeLog

+2013-03-16  Paolo Carlini  <paolo.carlini@oracle.com>
+
+	PR c++/56582
+	* semantics.c (cxx_eval_array_reference): Check for negative index.
+
 2013-03-14  Jason Merrill  <jason@redhat.com>
 
 	PR c++/56614

gcc/cp/semantics.c

@@ -7007,6 +7007,13 @@ cxx_eval_array_reference (const constexpr_call *call, tree t,
       *non_constant_p = true;
       return t;
     }
+  else if (tree_int_cst_lt (index, integer_zero_node))
+    {
+      if (!allow_non_constant)
+	error ("negative array subscript");
+      *non_constant_p = true;
+      return t;
+    }
   i = tree_low_cst (index, 0);
   if (TREE_CODE (ary) == CONSTRUCTOR)
     return (*CONSTRUCTOR_ELTS (ary))[i].value;

gcc/testsuite/ChangeLog

+2013-03-16  Paolo Carlini  <paolo.carlini@oracle.com>
+
+	PR c++/56582
+	* g++.dg/cpp0x/constexpr-array5.C: New.
+
 2013-03-15  Tobias Burnus  <burnus@net-b.de>
 
-	PR fortran/56615                                                                                                                
-	* gfortran.dg/transfer_intrinsic_5.f90: New.                                                                                    
+	PR fortran/56615
+	* gfortran.dg/transfer_intrinsic_5.f90: New.
 
 2013-03-15  Kai Tietz  <ktietz@redhat.com>
 

gcc/testsuite/g++.dg/cpp0x/constexpr-array5.C

+// PR c++/56582
+// { dg-do compile { target c++11 } }
+
+// Reliable ICE
+constexpr int n[3] = {};
+constexpr int k = n[-1];            // { dg-error "negative" }
+
+// Some random byte
+constexpr char c = "foo"[-1000];    // { dg-error "negative" }