使用clang和gcc编译时，代码不调用Move构造函数(Code not calling Move constructor when compiled with clang and gcc)

所以，这在GCC，CLANG和MSVC上编译得很好但是给出了不同的输出：

#include <iostream> using namespace std; class A { public: A() { cout << this << " def" << endl; } A(const A&) { cout << this << " copy" << endl; } A(A&&) { cout << this << " move" << endl; } A& operator= (const A&) { cout << this << " copy=" << endl; return *this; } A& operator= (A&&) { cout << this << " move=" << endl; return *this; } ~A() { cout << this << " ~A" << endl; } }; A f() { A a; return a; } int main(){ A a = f(); }

使用GCC和CLANG输出：

0xbfad67cf def 0xbfad67cf~A

虽然MSVC输出正如预期（C ++ 11标准）：

0039FA3B def 0039FA3B移动 0039FA3B~A

因此，使用MSVC调用的代码调用移动构造函数，而使用GCC和CLANG移动构造函数则不会调用。我也试过禁用优化，仍然得到相同的输出。更奇怪的是，当我改变f（）以返回A（）时，即使在MSVC上也不会调用移动构造函数。

编译器版本：

gcc：版本4.7.2（GCC） clang：版本3.2（标签/ RELEASE_32 / final）目标：i386-pc-linux-gnu

平台： Linux / ArchLinux

So, this compiles just fine on GCC, CLANG and MSVC but gives different output:

#include <iostream> using namespace std; class A { public: A() { cout << this << " def" << endl; } A(const A&) { cout << this << " copy" << endl; } A(A&&) { cout << this << " move" << endl; } A& operator= (const A&) { cout << this << " copy=" << endl; return *this; } A& operator= (A&&) { cout << this << " move=" << endl; return *this; } ~A() { cout << this << " ~A" << endl; } }; A f() { A a; return a; } int main(){ A a = f(); }

With GCC and CLANG outputs:

0xbfad67cf def 0xbfad67cf ~A

While with MSVC out is as expected (C++11 standard):

0039FA3B def 0039FA3B move 0039FA3B ~A

So, code compiled with MSVC calls move constructor, while with GCC and CLANG move constructor is not called. I also tried with optimizations disabled, and still get the same output. What is more strange is that when I change f() to return A(), move constructor is not called even on MSVC.

Compiler versions:

gcc: version 4.7.2 (GCC) clang: version 3.2 (tags/RELEASE_32/final) Target: i386-pc-linux-gnu

Platform: Linux/ArchLinux