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

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2010-01-27  Richard Guenther  <rguenther@suse.de>

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

From-SVN: r156290
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Richard Guenther 2010-01-27 15:49:00 +00:00 committed by Richard Biener
parent 9a78eb7197
commit 77597d3907
3 changed files with 27 additions and 6 deletions
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7
libstdc++-v3/ChangeLog
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@ -1,3 +1,10 @@
2010-01-27 Richard Guenther <rguenther@suse.de>
PR libstdc++/42832
* include/std/functional (function<>::swap): Perform bytewise
swap of _M_functor.
* include/tr1/functional (function<>::swap): Likewise.
2010-01-27 Andreas Krebbel <Andreas.Krebbel@de.ibm.com>
* config/abi/pre/gnu.ver: Avoid time_get pattern conflicts.

13
libstdc++-v3/include/std/functional
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@ -1940,9 +1940,16 @@ namespace std
*/
void swap(function& __x)
{
_Any_data __old_functor = _M_functor;
_M_functor = __x._M_functor;
__x._M_functor = __old_functor;
/* 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]);
_Manager_type __old_manager = _M_manager;
_M_manager = __x._M_manager;
__x._M_manager = __old_manager;

13
libstdc++-v3/include/tr1/functional
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@ -1904,9 +1904,16 @@ namespace tr1
*/
void swap(function& __x)
{
_Any_data __old_functor = _M_functor;
_M_functor = __x._M_functor;
__x._M_functor = __old_functor;
/* 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]);
_Manager_type __old_manager = _M_manager;
_M_manager = __x._M_manager;
__x._M_manager = __old_manager;