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re PR c++/51489 (constexpr not working consistently)

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PR c++/51489
	* semantics.c (cxx_eval_outermost_constant_expr): Check for
	conversion from pointer to integer here.
	(cxx_eval_constant_expression) [NOP_EXPR]: Not here.

From-SVN: r182470
This commit is contained in:
Jason Merrill 2011-12-19 00:57:52 -05:00 committed by Jason Merrill
parent a733dd3ded
commit 37ef545a76
4 changed files with 42 additions and 28 deletions
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7
gcc/cp/ChangeLog
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@ -1,3 +1,10 @@
2011-12-19 Jason Merrill <jason@redhat.com>
PR c++/51489
* semantics.c (cxx_eval_outermost_constant_expr): Check for
conversion from pointer to integer here.
(cxx_eval_constant_expression) [NOP_EXPR]: Not here.
2011-12-18 Paolo Carlini <paolo.carlini@oracle.com>
* semantics.c (finish_compound_literal): Don't call check_narrowing

44
gcc/cp/semantics.c
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@ -7704,17 +7704,6 @@ cxx_eval_constant_expression (const constexpr_call *call, tree t,
tree oldop = TREE_OPERAND (t, 0);
tree op = oldop;
tree to = TREE_TYPE (t);
tree source = TREE_TYPE (op);
if (TYPE_PTR_P (source) && ARITHMETIC_TYPE_P (to)
&& !(TREE_CODE (op) == COMPONENT_REF
&& TYPE_PTRMEMFUNC_P (TREE_TYPE (TREE_OPERAND (op, 0)))))
{
if (!allow_non_constant)
error ("conversion of expression %qE of pointer type "
"cannot yield a constant expression", op);
*non_constant_p = true;
return t;
}
op = cxx_eval_constant_expression (call, TREE_OPERAND (t, 0),
allow_non_constant, addr,
non_constant_p);
@ -7803,6 +7792,20 @@ cxx_eval_outermost_constant_expr (tree t, bool allow_non_constant)
non_constant_p = true;
}
/* Technically we should check this for all subexpressions, but that
runs into problems with our internal representation of pointer
subtraction and the 5.19 rules are still in flux. */
if (CONVERT_EXPR_CODE_P (TREE_CODE (r))
&& ARITHMETIC_TYPE_P (TREE_TYPE (r))
&& TREE_CODE (TREE_OPERAND (r, 0)) == ADDR_EXPR)
{
if (!allow_non_constant)
error ("conversion from pointer type %qT "
"to arithmetic type %qT in a constant-expression",
TREE_TYPE (TREE_OPERAND (r, 0)), TREE_TYPE (r));
non_constant_p = true;
}
if (non_constant_p && !allow_non_constant)
return error_mark_node;
else if (non_constant_p && TREE_CONSTANT (t))
@ -8110,25 +8113,10 @@ potential_constant_expression_1 (tree t, bool want_rval, tsubst_flags_t flags)
case NOP_EXPR:
case CONVERT_EXPR:
case VIEW_CONVERT_EXPR:
/* -- an array-to-pointer conversion that is applied to an lvalue
that designates an object with thread or automatic storage
duration; FIXME not implemented as it breaks constexpr arrays;
need to fix the standard
-- a type conversion from a pointer or pointer-to-member type
to a literal type. */
/* -- a reinterpret_cast. FIXME not implemented, and this rule
may change to something more specific to type-punning (DR 1312). */
{
tree from = TREE_OPERAND (t, 0);
tree source = TREE_TYPE (from);
tree target = TREE_TYPE (t);
if (TYPE_PTR_P (source) && ARITHMETIC_TYPE_P (target)
&& !(TREE_CODE (from) == COMPONENT_REF
&& TYPE_PTRMEMFUNC_P (TREE_TYPE (TREE_OPERAND (from, 0)))))
{
if (flags & tf_error)
error ("conversion of expression %qE of pointer type "
"cannot yield a constant expression", from);
return false;
}
return (potential_constant_expression_1
(from, TREE_CODE (t) != VIEW_CONVERT_EXPR, flags));
}

5
gcc/testsuite/ChangeLog
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@ -1,3 +1,8 @@
2011-12-19 Jason Merrill <jason@redhat.com>
PR c++/51489
* g++.dg/cpp0x/constexpr-ptrsub.C: New.
2011-12-18 Hans-Peter Nilsson <hp@axis.com>
* gcc.dg/pr51491-2.c: Fix "cleanup-treee-dump" typo.

14
gcc/testsuite/g++.dg/cpp0x/constexpr-ptrsub.C Normal file
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@ -0,0 +1,14 @@
// PR c++/51489
// DR 1313
// { dg-options "-std=c++0x" }
struct array
{
constexpr array() :x(0) {}
constexpr int const* begin() { return &x; }
int x;
};
constexpr array aa;
constexpr auto b = aa.begin();
static_assert(b-b == 0, "compiles just fine");
static_assert(aa.begin()-aa.begin() == 0, "compiler thinks it's not a constant expression");