什么是堆栈展开?

Stack unwinding is usually talked about in connection with exception handling. Here's an example:

void func( int x )
{
    char* pleak = new char[1024]; // might be lost => memory leak
    std::string s( "hello world" ); // will be properly destructed

    if ( x ) throw std::runtime_error( "boom" );

    delete [] pleak; // will only get here if x == 0. if x!=0, throw exception
}

int main()
{
    try
    {
        func( 10 );
    }
    catch ( const std::exception& e )
    {
        return 1;
    }

    return 0;
}

这里分配给pleak的内存如果抛出异常会丢失，而分配给s的内存会被std::string析构函数在任何情况下.当退出范围时，分配在堆栈上的对象被展开"(这里的范围是函数 func.)这是通过编译器插入对自动(堆栈)变量的析构函数的调用来完成的.