Hider
Here is a patch already posted to libstdc++ mailing but I am
resending following libstdc++ maintainers advises to add gcc-patches
mailing list.
This patch proposal is to fix the behavior of std::pair regarding
the std::is_*_assignable meta programming functions.
As announced it is requiring a compiler patch to extend DR 1402
resolution to all defaulted methods.
2013-04-12 François Dumont
* call.c (joust): Extend DR 1402 to all defaulted methods.
This modification is mandatory so that pair& operator=(const pair&)
can be defaulted whereas leaving gcc consider the other operator= in
some situations like std::pair. This way, with usage of
std::enable_if on the template operator=, we can control when p1= p2 is
a valid expression resulting in a correct behavior of
std::is_copy_assignable.
For the moment I preferred to add a dg-require-normal-mode option
in the single test that fail to compile because of the compiler
modification.
Does DR 1402 resolution generalization need a Standard committee
validation first ?
2013-04-13 François Dumont
* include/bits/stl_pair.h (operator=(const pair&)): Defaulted.
(operator=(pair&&)): Likewise.
(template<> operator=(const pair&)): Add noexcept
qualification. Enable if is_assignable true for both
parameters.
(template<> operator=(pair<>&&)): Add noexcept
qualification. Enable if is_assignable true for both
parameters.
* testsuite/23_containers/unordered_set/55043.cc: Add
dg-require-normal-mode.
* testsuite/20_util/pair/is_move_assignable.cc: New.
* testsuite/20_util/pair/is_copy_assignable.cc: Likewise.
* testsuite/20_util/pair/is_assignable.cc: Likewise.
* testsuite/20_util/pair/is_nothrow_move_assignable.cc: Likewise.
* testsuite/20_util/pair/assign_neg.cc: Likewise.
* testsuite/20_util/pair/is_nothrow_copy_assignable.cc: Likewise.
* testsuite/20_util/pair/assign.cc: Likewise.
François
Index: call.c
===
--- call.c (revision 197829)
+++ call.c (working copy)
@@ -8377,19 +8377,20 @@
&& (IS_TYPE_OR_DECL_P (cand1->fn)))
return 1;
- /* Prefer a non-deleted function over an implicitly deleted move
- constructor or assignment operator. This differs slightly from the
- wording for issue 1402 (which says the move op is ignored by overload
- resolution), but this way produces better error messages. */
+ /* Prefer a non-deleted function over an implicitly deleted one. This
+ differs slightly from the wording for issue 1402 because:
+ - it is extended to all defaulted functions, not only the ones with
+ move semantic
+ - it says the op is ignored by overload resolution while we are
+ only making it a worst candidate, but this way produces better error
+ messages. */
if (TREE_CODE (cand1->fn) == FUNCTION_DECL
&& TREE_CODE (cand2->fn) == FUNCTION_DECL
&& DECL_DELETED_FN (cand1->fn) != DECL_DELETED_FN (cand2->fn))
{
- if (DECL_DELETED_FN (cand1->fn) && DECL_DEFAULTED_FN (cand1->fn)
- && move_fn_p (cand1->fn))
+ if (DECL_DELETED_FN (cand1->fn) && DECL_DEFAULTED_FN (cand1->fn))
return -1;
- if (DECL_DELETED_FN (cand2->fn) && DECL_DEFAULTED_FN (cand2->fn)
- && move_fn_p (cand2->fn))
+ if (DECL_DELETED_FN (cand2->fn) && DECL_DEFAULTED_FN (cand2->fn))
return 1;
}
Index: include/bits/stl_pair.h
===
--- include/bits/stl_pair.h (revision 197829)
+++ include/bits/stl_pair.h (working copy)
@@ -155,26 +155,18 @@
pair(piecewise_construct_t, tuple<_Args1...>, tuple<_Args2...>);
pair&
- operator=(const pair& __p)
- {
- first = __p.first;
- second = __p.second;
- return *this;
- }
+ operator=(const pair&) = default;
pair&
- operator=(pair&& __p)
- noexcept(__and_,
- is_nothrow_move_assignable<_T2>>::value)
- {
- first = std::forward(__p.first);
- second = std::forward(__p.second);
- return *this;
- }
+ operator=(pair&&) = default;
template
- pair&
+ typename enable_if<__and_,
+ is_assignable<_T2&, const _U2&>>::value,
+ pair&>::type
operator=(const pair<_U1, _U2>& __p)
+ noexcept(__and_,
+ is_nothrow_assignable<_T2&, const _U2&>>::value)
{
first = __p.first;
second = __p.second;
@@ -182,8 +174,12 @@
}
template
- pair&
+ typename enable_if<__and_,
+ is_assignable<_T2&, _U2&&>>::value,
+ pair&>::type
operator=(pair<_U1, _U2>&& __p)
+ noexcept(__and_,
+ is_nothrow_assignable<_T2&, _U2&&>>::value)
{
first = std::forward<_U1>(__p.first);
second = std::forward<_U2>(__p.second);
Index: testsuite/23_containers/unordered_set/55043.cc
===
--- testsuite/23_containers/unordered_set/55043.cc (revision 197829)
+++ test
