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re PR c++/58102 (rejects valid initialization of constexpr object with mutable member)

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PR c++/58102
	* typeck2.c (store_init_value): Set it.
	* cp-tree.h (CONSTRUCTOR_MUTABLE_POISON): New.
	* constexpr.c (cxx_eval_outermost_constant_expr): Check it.

From-SVN: r217713
This commit is contained in:
Jason Merrill 2014-11-18 08:34:08 -05:00 committed by Jason Merrill
parent bee1d47857
commit 023d89c70b
5 changed files with 34 additions and 7 deletions
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7
gcc/cp/ChangeLog
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@ -1,3 +1,10 @@
2014-11-18 Jason Merrill <jason@redhat.com>
PR c++/58102
* typeck2.c (store_init_value): Set it.
* cp-tree.h (CONSTRUCTOR_MUTABLE_POISON): New.
* constexpr.c (cxx_eval_outermost_constant_expr): Check it.
2014-11-17 Jason Merrill <jason@redhat.com>
PR c++/33911

14
gcc/cp/constexpr.c
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@ -3315,15 +3315,15 @@ cxx_eval_outermost_constant_expr (tree t, bool allow_non_constant,
verify_constant (r, allow_non_constant, &non_constant_p, &overflow_p);
if (TREE_CODE (t) != CONSTRUCTOR
&& cp_has_mutable_p (TREE_TYPE (t)))
/* Mutable logic is a bit tricky: we want to allow initialization of
constexpr variables with mutable members, but we can't copy those
members to another constexpr variable. */
if (TREE_CODE (r) == CONSTRUCTOR
&& CONSTRUCTOR_MUTABLE_POISON (r))
{
/* We allow a mutable type if the original expression was a
CONSTRUCTOR so that we can do aggregate initialization of
constexpr variables. */
if (!allow_non_constant)
error ("%qT cannot be the type of a complete constant expression "
"because it has mutable sub-objects", type);
error ("%qE is not a constant expression because it refers to "
"mutable subobjects of %qT", t, type);
non_constant_p = true;
}

6
gcc/cp/cp-tree.h
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@ -109,6 +109,7 @@ c-common.h, not after.
DECLTYPE_FOR_LAMBDA_PROXY (in DECLTYPE_TYPE)
REF_PARENTHESIZED_P (in COMPONENT_REF, INDIRECT_REF)
AGGR_INIT_ZERO_FIRST (in AGGR_INIT_EXPR)
CONSTRUCTOR_MUTABLE_POISON (in CONSTRUCTOR)
3: (TREE_REFERENCE_EXPR) (in NON_LVALUE_EXPR) (commented-out).
ICS_BAD_FLAG (in _CONV)
FN_TRY_BLOCK_P (in TRY_BLOCK)
@ -3497,6 +3498,11 @@ more_aggr_init_expr_args_p (const aggr_init_expr_arg_iterator *iter)
#define CONSTRUCTOR_NO_IMPLICIT_ZERO(NODE) \
(TREE_LANG_FLAG_1 (CONSTRUCTOR_CHECK (NODE)))
/* True if this CONSTRUCTOR should not be used as a variable initializer
because it was loaded from a constexpr variable with mutable fields. */
#define CONSTRUCTOR_MUTABLE_POISON(NODE) \
(TREE_LANG_FLAG_2 (CONSTRUCTOR_CHECK (NODE)))
#define DIRECT_LIST_INIT_P(NODE) \
(BRACE_ENCLOSED_INITIALIZER_P (NODE) && CONSTRUCTOR_IS_DIRECT_INIT (NODE))

4
gcc/cp/typeck2.c
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@ -809,6 +809,10 @@ store_init_value (tree decl, tree init, vec<tree, va_gc>** cleanups, int flags)
value = cxx_constant_value (value, decl);
}
value = maybe_constant_init (value, decl);
if (TREE_CODE (value) == CONSTRUCTOR && cp_has_mutable_p (type))
/* Poison this CONSTRUCTOR so it can't be copied to another
constexpr variable. */
CONSTRUCTOR_MUTABLE_POISON (value) = true;
const_init = (reduced_constant_expression_p (value)
|| error_operand_p (value));
DECL_INITIALIZED_BY_CONSTANT_EXPRESSION_P (decl) = const_init;

10
gcc/testsuite/g++.dg/cpp0x/constexpr-mutable2.C Normal file
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@ -0,0 +1,10 @@
// PR c++/58102
// { dg-do compile { target c++11 } }
struct S {
mutable int n;
constexpr S() : n() {}
};
constexpr S s = {};
constexpr S s2 = s; // { dg-error "mutable" }