c++ - 使用SEH时如何解释GetExceptionCode结果？

我一直在尝试编写一些错误保护子句，以识别由第三方提供给我们的dll中的问题。该dll中可能存在问题(内存异常，浮点错误等)，并且能够在不访问源代码的情况下识别这些错误是有利的。

我从各种SEH错误处理例程中收集了一些信息，但是虽然可以正常工作，但还是有一些...不一致之处。我试图隔离每个人，并且我将分别对每个人提出一个问题。

这与在SEH __try / __ except子句中用于识别错误的GetExceptionCode有关。它似乎不能可靠地做到这一点。

这是一个很明显的被零除的情况:

#include <float.h>      // defines of _EM_OVERFLOW, etc.
#include <string.h>     // strncpy_s & strncat_s
#include <stdlib.h>     // malloc
#include <excpt.h>      // EXCEPTION_EXECUTE_HANDLER
#include <iostream>     // cout
#include <bitset>       // bitset
#include <conio.h>      // _kbhit
#pragma fenv_access (on)


const unsigned int SERIOUS_FP_EXCEPTIONS = _EM_DENORMAL | _EM_ZERODIVIDE | _EM_INVALID;
const unsigned int MINOR_FP_EXCEPTIONS = _EM_OVERFLOW | _EM_UNDERFLOW | _EM_INEXACT;

int main(int argc, char[])
{
    double numerator = 1.0;
    double denominator = 0.0;
    double result = 0.0;

    unsigned int _previous_floating_point_control;
    _controlfp_s(&_previous_floating_point_control, 0, 0);
    _controlfp_s(nullptr, MINOR_FP_EXCEPTIONS, _MCW_EM);
    __try {
        result = numerator / denominator;
        _controlfp_s(NULL, _previous_floating_point_control, _MCW_EM);
    }
    __except (EXCEPTION_EXECUTE_HANDLER)
    {
        std::cout << "_EM_INEXACT    = " << std::bitset<32>(_EM_INEXACT) << std::endl;
        std::cout << "_EM_UNDERFLOW  = " << std::bitset<32>(_EM_UNDERFLOW) << std::endl;
        std::cout << "_EM_OVERFLOW   = " << std::bitset<32>(_EM_OVERFLOW) << std::endl;
        std::cout << "_EM_ZERODIVIDE = " << std::bitset<32>(_EM_ZERODIVIDE) << std::endl;
        std::cout << "_EM_INVALID    = " << std::bitset<32>(_EM_INVALID) << std::endl;
        std::cout << "_EM_DENORMAL   = " << std::bitset<32>(_EM_DENORMAL) << std::endl;
        std::cout << "_EM_AMBIGUOUS  = " << std::bitset<32>(_EM_AMBIGUOUS) << std::endl;
        std::cout << std::endl;
        std::cout << "                                      divide-by-zero" << std::endl;
        std::cout << "                                             |" << std::endl;
        std::cout << "            ambiguous code?                underflow" << std::endl;
        std::cout << "                  |                          : |" << std::endl;
        std::cout << "                  v                          v v" << std::endl;
        std::cout << "Exception code = " << std::bitset<32>(GetExceptionCode()) << std::endl;
        std::cout << "                             ^              ^ ^ ^" << std::endl;
        std::cout << "                             |              : : |" << std::endl;
        std::cout << "                     denormal number     inexact number" << std::endl;
        std::cout << "                                            : |" << std::endl;
        std::cout << "                                          overflow" << std::endl;
        std::cout << "                                            |" << std::endl;
        std::cout << "                                     invalid number" << std::endl;

        if (GetExceptionCode() & _EM_ZERODIVIDE)
            std::cout << "ERROR! Divide By Zero!" << std::endl;
        else
            std::cout << "No divide by zero found here!" << std::endl;
        _controlfp_s(NULL, _previous_floating_point_control, _MCW_EM);
    }

    std::cout << "result = " << result << std::endl;

    while (!_kbhit())   // Wait until a key is pressed to close console.
    { }
}

这将打印以下内容:

_EM_INEXACT    = 00000000000000000000000000000001
_EM_UNDERFLOW  = 00000000000000000000000000000010
_EM_OVERFLOW   = 00000000000000000000000000000100
_EM_ZERODIVIDE = 00000000000000000000000000001000
_EM_INVALID    = 00000000000000000000000000010000
_EM_DENORMAL   = 00000000000010000000000000000000
_EM_AMBIGUOUS  = 10000000000000000000000000000000

                                      divide-by-zero
                                             |
            ambiguous code?                underflow
                  |                          : |
                  v                          v v
Exception code = 11000000000000000000001010110101
                             ^              ^ ^ ^
                             |              : : |
                     denormal number     inexact number
                                            : |
                                          overflow
                                            |
                                     invalid number
No divide by zero found here!
result = 0

它已识别出一个问题(严重)，但尚未完全正确诊断。

更糟糕的是，当子句被缺少依赖项的dll调用所替代时，我得到:

                       f.p. exceptions
     denormal number         |
            |               _|_
            v              /   \
11000000011011010000000001111110
         ^^  ^ ^         ^^
         ||  | |         ||
         \________________/
           unknown codes

如果发生SIGSEV错误(分段错误)，则返回相似的结果。这意味着我们将其他问题误诊断为浮点异常。

所以我的问题是:

这个一般方法正确吗，还是我误会了什么
基本的？

为什么没有采用除零的简单情况？是否取决于硬件？

我可以找出其余的错误位来自GetExceptionCode()的情况吗-这真的很有用。

PS:请不要发表评论或回答我应该检查分母是否为0-我知道，我在我可以控制的所有代码中都这样做。

最佳答案

您将需要一些类似的东西

DWORD exception_filter(DWORD dwExceptionCode)
{
    // use dwExceptionCode to handle only the types of exceptions you want
    // if you want to use it inside your handler, you'll need to save it.
    return EXCEPTION_EXECUTE_HANDLER; // or other value depending on ExceptionCode
}

Your exception handler...

__try
{
    something();
}
__except (exception_filter(GetExceptionCode())
{
    // DO NOT CALL GetExceptionCode() or GetExceptionInfo() here. If you need
    // Exception Info as well, pass it to the filter, and save the values you need.
    switch (dwSavedExceptionCode)
    {
        case EXCEPTION_FLT_OVERFLOW:
              ItWasAFloatingPointOverflow();
              break;
        case EXCEPTION_FLT_DIVIDE_BY_ZERO:
              ItWasAFloatingDivideByZero();
              break;
        case ***Other Exception Types You Want handled (==the ones you returned execute_handler for in the filter) ***
              break;
    }
}

关于c++ - 使用SEH时如何解释GetExceptionCode结果？，我们在Stack Overflow上找到一个类似的问题：https://stackoverflow.com/questions/41505721/