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revert: re PR libstdc++/42832 (Revisit std::function for aliasing issues and efficiency) 

Revert:
	PR libstdc++/42832
	* include/std/functional (function<>::swap): Perform bytewise
	swap of _M_functor.
	* include/tr1/functional (function<>::swap): Likewise.

From-SVN: r159940
This commit is contained in:
Jason Merrill 2010-05-27 14:39:46 -04:00 committed by Jason Merrill
parent 6ab4e49cf0
commit fb9c3174c9
3 changed files with 14 additions and 20 deletions
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8
libstdc++-v3/ChangeLog
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@ -1,3 +1,11 @@
2010-05-27 Jason Merrill <jason@redhat.com>
Revert:
PR libstdc++/42832
* include/std/functional (function<>::swap): Perform bytewise
swap of _M_functor.
* include/tr1/functional (function<>::swap): Likewise.
2010-05-27 Paolo Carlini <paolo.carlini@oracle.com>
PR libstdc++/40497

13
libstdc++-v3/include/std/functional
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@ -1948,16 +1948,9 @@ namespace std
*/
void swap(function& __x)
{
/* We cannot perform direct assignments of the _M_functor
parts as they are of type _Any_data and have a different
dynamic type. Doing so would violate type-based aliasing
rules and lead to spurious miscompilations.
Instead perform a bytewise exchange of the memory of
both POD objects.
??? A wordwise exchange honoring alignment of _M_functor
would be more efficient. See PR42845. */
for (unsigned i = 0; i < sizeof (_M_functor._M_pod_data); ++i)
std::swap (_M_functor._M_pod_data[i], __x._M_functor._M_pod_data[i]);
_Any_data __old_functor = _M_functor;
_M_functor = __x._M_functor;
__x._M_functor = __old_functor;
_Manager_type __old_manager = _M_manager;
_M_manager = __x._M_manager;
__x._M_manager = __old_manager;

13
libstdc++-v3/include/tr1/functional
View File

@ -1907,16 +1907,9 @@ namespace tr1
*/
void swap(function& __x)
{
/* We cannot perform direct assignments of the _M_functor
parts as they are of type _Any_data and have a different
dynamic type. Doing so would violate type-based aliasing
rules and lead to spurious miscompilations.
Instead perform a bytewise exchange of the memory of
both POD objects.
??? A wordwise exchange honoring alignment of _M_functor
would be more efficient. See PR42845. */
for (unsigned i = 0; i < sizeof (_M_functor._M_pod_data); ++i)
std::swap (_M_functor._M_pod_data[i], __x._M_functor._M_pod_data[i]);
_Any_data __old_functor = _M_functor;
_M_functor = __x._M_functor;
__x._M_functor = __old_functor;
_Manager_type __old_manager = _M_manager;
_M_manager = __x._M_manager;
__x._M_manager = __old_manager;