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| author | Richard Guenther <rguenther@suse.de> | 2010-01-27 15:49:00 +0000 |
|---|---|---|
| committer | Richard Biener <rguenth@gcc.gnu.org> | 2010-01-27 15:49:00 +0000 |
| commit | 77597d3907e17a45b0d4825edb893c23a0715181 (patch) | |
| tree | 41da2c42473b85d27731c803582dd08dd982c329 | |
| parent | 9a78eb7197d02a89c12859159f9e0c32c740701b (diff) | |
| download | gcc-77597d3907e17a45b0d4825edb893c23a0715181.zip gcc-77597d3907e17a45b0d4825edb893c23a0715181.tar.gz gcc-77597d3907e17a45b0d4825edb893c23a0715181.tar.bz2 | |
re PR libstdc++/42832 (Revisit std::function for aliasing issues and efficiency)
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
| -rw-r--r-- | libstdc++-v3/ChangeLog | 7 | ||||
| -rw-r--r-- | libstdc++-v3/include/std/functional | 13 | ||||
| -rw-r--r-- | libstdc++-v3/include/tr1/functional | 13 |
3 files changed, 27 insertions, 6 deletions
diff --git a/libstdc++-v3/ChangeLog b/libstdc++-v3/ChangeLog index 4e5adf7..25cda7e 100644 --- a/libstdc++-v3/ChangeLog +++ b/libstdc++-v3/ChangeLog @@ -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. diff --git a/libstdc++-v3/include/std/functional b/libstdc++-v3/include/std/functional index 29b19f6..c390c3b 100644 --- a/libstdc++-v3/include/std/functional +++ b/libstdc++-v3/include/std/functional @@ -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; diff --git a/libstdc++-v3/include/tr1/functional b/libstdc++-v3/include/tr1/functional index 4825509..2052f88 100644 --- a/libstdc++-v3/include/tr1/functional +++ b/libstdc++-v3/include/tr1/functional @@ -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; |