有两个向量std :: vector和QVector.我们必须检查插入时“移位”元素的方式. (用五个元素构造两个向量并插入零元素)我有这个代码：
#include <QVector>
#include <QTextStream>
struct MoveTest
{
int i;
MoveTest() {}
MoveTest(const MoveTest& other) {QTextStream(stdout) << "constr copy" << endl;}
MoveTest(MoveTest &&other) {QTextStream(stdout) << "constr move" << endl;}
~MoveTest() {}
inline MoveTest& operator= (const MoveTest& other) {QTextStream(stdout) << "copy" << endl;}
inline MoveTest& operator= (MoveTest &&other) {QTextStream(stdout) << "move" << endl;}
};
int main(int argc,char *argv[])
{
QTextStream(stdout) << "std::move:" << endl;
MoveTest t1;
MoveTest t2(std::move(t1));
t1 = std::move(t2);
QTextStream(stdout) << "QVector:" << endl;
QVector<MoveTest> qmTest(5);
qmTest.insert(qmTest.begin(),MoveTest());
QTextStream(stdout) << "std::vector:" << endl;
std::vector<MoveTest> mTest(5);
mTest.insert(mTest.begin(),MoveTest());
return 0;
}
我的输出是gcc 4.7.2,QMAKE_CXXFLAGS = -std = c 0x：
std::move: constr move move QVector: constr copy constr copy constr copy constr copy constr copy constr copy copy copy copy copy copy copy std::vector: constr move constr copy constr copy constr copy constr copy constr copy
如何在不复制的情况下插入具有内部移位的元素？需要什么GCC标志？
解决方法
由于您的move运算符可以抛出异常,因此std :: vector无法使用它.如果运算符在调整大小过程中途抛出异常,它会怎么做？如果它不能抛出异常并且向量实现可以使用它,则声明它为
noexcept.