boost::container::vector fails to compile with C++03 compiler
The following example compiles fine when using GCC 4.4.6 with the --std=c++0x
flag but fails to compile in C++03 mode.
#include
It appears that this is a limitation as explained here: http://www.boost.org/doc/libs/1_51_0/doc/html/move/emulation_limitations.htm... -- View this message in context: http://boost.2283326.n4.nabble.com/boost-container-vector-fails-to-compile-w... Sent from the Boost - Users mailing list archive at Nabble.com.
seems It's trying to use movable objects and this is supported only in
C++11 STL
On Fri, Oct 26, 2012 at 2:30 PM, mark pashley
It appears that this is a limitation as explained here:
http://www.boost.org/doc/libs/1_51_0/doc/html/move/emulation_limitations.htm...
-- View this message in context: http://boost.2283326.n4.nabble.com/boost-container-vector-fails-to-compile-w... Sent from the Boost - Users mailing list archive at Nabble.com. _______________________________________________ Boost-users mailing list Boost-users@lists.boost.org http://lists.boost.org/mailman/listinfo.cgi/boost-users
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On Fri, Oct 26, 2012 at 4:00 AM, mark pashley
It appears that this is a limitation as explained here:
http://www.boost.org/doc/libs/1_51_0/doc/html/move/emulation_limitations.htm...
This is indeed the issue. Basically, if struct data { boost::container::vector<int> x; }; then data turns out not to be const-assignable in C++03, due to the existence of a vector::operator=(vector &) overload rather than vector::operator=(vector const &). To get things functional, all you should have to do is explicitly define a data::operator=(data const &) (which does memberwise assignment), but to enable move semantics (which would be desirable if you had a boost::container::vector<data> as in your snipped example) you would indeed need to define a move constructor and move assignment operator (and default constructor if needed; I think you can get away with using the compiler-generated copy constructor). I would consider this a usability problem as it's error-prone (adding another member to the data struct but forgetting to include it in any or all of the move constructor or copy/move assignment operators is entirely possible) and tedious. This is why I've created macros to automate the generation of this boilerplate (and expand to nothing or the "= default" versions in C++11), and may be something Ion should consider adding. E.g., template< class First, class Second > struct pair { First first; Second second; BOOST_MOVABLE_COPYABLE_MEMBERWISE( typename pair, (( First )( first )) (( Second )( second )) ) }; Incidentally, with some additional complexity, the above macro can enable the move emulation machinery in C++03 iff either of First or Second is movable. If desired, I can see about packaging these up for inclusion in Boost.Move. - Jeff
If desired, I can see about packaging these up for inclusion in Boost.Move.
Sounds Good! Regards, Mark -- View this message in context: http://boost.2283326.n4.nabble.com/boost-container-vector-fails-to-compile-w... Sent from the Boost - Users mailing list archive at Nabble.com.
participants (4)
-
Hassan Monfared
-
Ion Gaztañaga
-
Jeffrey Lee Hellrung, Jr.
-
mark pashley