Is std::ofstream movable?

问题

I have this map which compiles fine in MSVC10 :

std::map<std::string, std::ofstream> m_logFiles;

But on ubuntu using g++ 4.5 with C++0x enabled, I get the following error message :

/usr/include/c++/4.5/bits/ios_base.h|785|error: ‘std::ios_base::ios_base(const std::ios_base&)’ is private

By using pointers instead of objects, I resolved the problem.
Searching on the web, I learned that streams are not meant to be copied (the why was well explained). But my question is, is std::ofstream a movable type ? If it is, shouldn't it allow its use as a template parameter in the standard containers ?
If yes, then is g++ behind MSVC10 on this point ? (which would explain why it works on MSVC). I know it would be silly to ask compiler writers to fully implement something that isn't even final, but I'm curious regarding the future.

Using g++ 4.6.1 didn't help.

Edit : reading the comments I dug a little bit further and found that the insert is causing the problem, not the declaration of the map.

Reading Cubbi's link I tried the following :

#include <string>
#include <fstream>
#include <map>

using namespace std;

int main()
{
    map<string, ofstream> m_logFiles;
    ofstream st;
    m_logFiles.insert(make_pair<string, ofstream>(string("a"), move(st)));
    return 0;
}

But still no luck. g++ complains about the use of b deleted copy constructor.

回答1:

std::ofstream is movable. This program compiles for me using clang/libc++:

#include <string>
#include <fstream>
#include <map>

int main()
{
    std::map<std::string, std::ofstream> m_logFiles;
}

Reference 27.9.1.11 [ofstream.cons].

回答2:

I asked a similar question earlier, and later found that GCC doesn't seem to support movable fstreams yet (I just tested GCC 4.6.1) as detailed in this answer.

来源：https://stackoverflow.com/questions/7066691/is-stdofstream-movable

标签

c++

c++11

ofstream