什么是堆栈展开? [英] What is stack unwinding?

问题描述

什么是堆栈展开?搜索了一遍，但找不到有启发性的答案！

What is stack unwinding? Searched through but couldn't find enlightening answer!

推荐答案

堆栈展开通常与异常处理有关.这是一个例子:

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.

Here memory allocated for pleak will be lost if an exception is thrown, while memory allocated to s will be properly released by std::string destructor in any case. The objects allocated on the stack are "unwound" when the scope is exited (here the scope is of the function func.) This is done by the compiler inserting calls to destructors of automatic (stack) variables.

现在这是一个非常强大的概念，导致了称为 RAII 的技术，即 Resource Acquisition Is Initialization，帮助我们管理 C++ 中的内存、数据库连接、打开文件描述符等资源.

Now this is a very powerful concept leading to the technique called RAII, that is Resource Acquisition Is Initialization, that helps us manage resources like memory, database connections, open file descriptors, etc. in C++.

现在我们可以提供异常安全保证.

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