C++:一个 std::runtime_error 对象会在 longjmp 中泄漏吗？

Question

假设我有一些 C++ 代码，它有一个 try-catch 块，其中 catch部分将触发跳远:

#include <stdexcept>
#include <stdio.h>
#include <setjmp.h>

void my_fun()
{
    jmp_buf jump_buffer;
    if (setjmp(jump_buffer))
        return;
    
    try {
        std::string message;
        message.resize(100);
        snprintf(&message[0], 100, "error code %d\n", 3);
        throw std::runtime_error(message);
    }

    catch (std::runtime_error &e) {
        longjmp(jump_buffer, 1);
    }
}

自 std::runtime_error对象是在某处动态分配的，它会泄漏为其或字符串分配的内存吗？

Answer 1

这有点复杂。关于 longjmp的有效性，the standard says:

A setjmp/longjmp call pair has undefined behavior if replacing the setjmp and longjmp by catch and throw would invoke any non-trivial destructors for any objects with automatic storage duration.

runtime_error有一个非平凡的析构函数，所以问题是异常对象是否具有“自动存储持续时间”。它不是。这表明 longjmp应该没事。
此外，exception object destruction can happen in one of two places :

The points of potential destruction for the exception object are:

• when an active handler for the exception exits by any means other than rethrowing, immediately after the destruction of the object (if any) declared in the exception-declaration in the handler;

• when an object of type std​::​exception_­ptr that refers to the exception object is destroyed, before the destructor of std​::​exception_­ptr returns.

longjmp不是“重投”。所以理论上，由于第 1 点，这应该没问题。
话虽如此，永远不要依赖这个 .我非常怀疑 longjmp 的实现正确处理这个问题，即使有些人这样做了，也可能不是你能预料到的。