SetJmp / LongJmp：为什么这会抛出segfault？ [英] SetJmp/LongJmp: Why is this throwing a segfault?

问题描述

以下代码总结了我目前遇到的问题。我目前的执行流程如下，我在GCC 4.3中运行。

The following code summarizes the problem I have at the moment. My current execution flow is as follows and a I'm running in GCC 4.3.

jmp_buf a_buf;
jmp_buf b_buf;

void b_helper()
{
    printf("entering b_helper");
    if(setjmp(b_buf) == 0)
    {
    	printf("longjmping to a_buf");
    	longjmp(a_buf, 1);
    }
    printf("returning from b_helper");
    return; //segfaults right here
}
void b()
{
    b_helper();
}
void a()
{
    printf("setjmping a_buf");
    if(setjmp(a_buf) == 0)
    {
    	printf("calling b");
    	b();
    }
    printf("longjmping to b_buf");
    longjmp(b_buf, 1);
}
int main()
{
    a();
}

上述执行流程在b_helper中返回后立即创建一个segfault。它几乎就像只有b_helper堆栈框架是有效的，它下面的堆栈被擦除。

The above execution flow creates a segfault right after the return in b_helper. It's almost as if only the b_helper stack frame is valid, and the stacks below it are erased.

任何人都可以解释为什么会发生这种情况？我猜这是一个GCC优化，它正在擦除未使用的堆栈帧或某事。

Can anyone explain why this is happening? I'm guessing it's a GCC optimization that's erasing unused stack frames or something.

谢谢。

推荐答案

只有 longjmp（）回到调用堆栈。调用 longjmp（b_buf，1）是事情开始出错的地方，因为 b_buf longjmp

You can only longjmp() back up the call stack. The call to longjmp(b_buf, 1) is where things start to go wrong, because the stack frame referenced by b_buf no longer exists after the longjmp(a_buf).

/ code>：

From the documentation for longjmp:

在调用setjmp（）例程返回的例程之后，可能不会调用longjmp

The longjmp() routines may not be called after the routine which called the setjmp() routines returns.

这包括通过 longjmp（） 。

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