Hi!
The following patch fixes a bunch of issues in
cxx_eval_pointer_plus_expression:
1) as it does STRIP_NOPS, the pointed type can change, and thus the
op01 constant in p+ might not be divisible by the other type size
2) we should restore the original type, rather than returning expression
of type after STRIP_NOPS
3) just in case, I've added a check TYPE_SIZE_UNIT is a constant
Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?
2015-04-11 Jakub Jelinek <ja...@redhat.com>
PR c++/65736
* constexpr.c (cxx_eval_pointer_plus_expression): Don't fold for VLAs,
don't fold if op01 isn't divisible by TYPE_SIZE_UNIT. Convert
the expression to the original type at the end.
* g++.dg/cpp0x/pr65736.C: New test.
--- gcc/cp/constexpr.c.jj 2015-04-03 15:32:31.000000000 +0200
+++ gcc/cp/constexpr.c 2015-04-11 10:28:12.154482385 +0200
@@ -2929,6 +2929,7 @@ cxx_eval_pointer_plus_expression (const
bool lval, bool *non_constant_p,
bool *overflow_p)
{
+ tree orig_type = TREE_TYPE (t);
tree op00 = TREE_OPERAND (t, 0);
tree op01 = TREE_OPERAND (t, 1);
location_t loc = EXPR_LOCATION (t);
@@ -2945,7 +2946,9 @@ cxx_eval_pointer_plus_expression (const
/* &A[i] p+ j => &A[i + j] */
if (TREE_CODE (op00) == ARRAY_REF
&& TREE_CODE (TREE_OPERAND (op00, 1)) == INTEGER_CST
- && TREE_CODE (op01) == INTEGER_CST)
+ && TREE_CODE (op01) == INTEGER_CST
+ && TYPE_SIZE_UNIT (TREE_TYPE (op00))
+ && TREE_CODE (TYPE_SIZE_UNIT (TREE_TYPE (op00))) == INTEGER_CST)
{
tree type = TREE_TYPE (op00);
t = fold_convert_loc (loc, ssizetype, TREE_OPERAND (op00, 1));
@@ -2953,15 +2956,21 @@ cxx_eval_pointer_plus_expression (const
/* Don't fold an out-of-bound access. */
if (!tree_int_cst_le (t, nelts))
return NULL_TREE;
+ op01 = cp_fold_convert (ssizetype, op01);
+ /* Don't fold if op01 can't be divided exactly by TYPE_SIZE_UNIT.
+ constexpr int A[1]; ... (char *)&A[0] + 1 */
+ if (!integer_zerop (fold_build2_loc (loc, TRUNC_MOD_EXPR, sizetype,
+ op01, TYPE_SIZE_UNIT (type))))
+ return NULL_TREE;
/* Make sure to treat the second operand of POINTER_PLUS_EXPR
as signed. */
- op01 = fold_build2_loc (loc, EXACT_DIV_EXPR, ssizetype,
- cp_fold_convert (ssizetype, op01),
+ op01 = fold_build2_loc (loc, EXACT_DIV_EXPR, ssizetype, op01,
TYPE_SIZE_UNIT (type));
t = size_binop_loc (loc, PLUS_EXPR, op01, t);
t = build4_loc (loc, ARRAY_REF, type, TREE_OPERAND (op00, 0),
t, NULL_TREE, NULL_TREE);
t = cp_build_addr_expr (t, tf_warning_or_error);
+ t = cp_fold_convert (orig_type, t);
return cxx_eval_constant_expression (ctx, t, lval, non_constant_p,
overflow_p);
}
--- gcc/testsuite/g++.dg/cpp0x/pr65736.C.jj 2015-04-11 10:32:06.807729783
+0200
+++ gcc/testsuite/g++.dg/cpp0x/pr65736.C 2015-04-11 10:31:11.000000000
+0200
@@ -0,0 +1,5 @@
+// PR c++/65736
+// { dg-do compile { target c++11 } }
+
+int a[1];
+char *b[1] { (char *)&a[0] + 1 };
Jakub
