Does std::move on std::string garantee that .c_str() returns same result?

Question

I want to provide zero-copy, move based API. I want to move a string from thread A into thread B. Ideologically it seems that move shall be able to simply pass\move data from instance A into new instance B with minimal to none copy operations (mainly for addresses). So all data like data pointers will be simply copied no new instance (constructed via move). So does std::move on std::string garantee that .c_str() returns same result on instance before move and instance created via move constructor?

Answer 1

No,

but if that is needed, an option is to put the string in std::unique_ptr. Personally I would typically not rely on the c_str() value for more than the local scope.

Example, on request:

#include <iostream>
#include <string>
#include <memory>

int main() {
    std::string ss("hello");
    auto u_str = std::make_unique<std::string>(ss);
    std::cout << u_str->c_str() <<std::endl;
    std::cout << *u_str <<std::endl;
    return 0;
}

if you don't have make_unique (new in C++14).

auto u_str = std::unique_ptr<std::string>(new std::string(ss));

Or just copy the whole implementation from the proposal by S.T.L.:

Ideone example on how to do that