核心文件完全是废话，或者这段代码真的抛出了 SIGFPE 吗？

发布于 2024-10-03 04:40:26 字数 632 浏览 9 评论 0原文

抛出了 SIGFPE。

我的核心文件声称从第 176 行的gcc-4.3.4/include/c++/4.3.4/bits/stl_iterator_base_funcs.h

这在这里：

  template<typename _InputIterator, typename _Distance>
    inline void
    advance(_InputIterator& __i, _Distance __n)
    {
          // concept requirements -- taken care of in __advance
176---->  typename iterator_traits<_InputIterator>::difference_type __d = __n;
          std::__advance(__i, __d, std::__iterator_category(__i));
    }

这是在我拥有的另一个函数内，该函数确实在调用 advance around通过不执行任何浮点运算的代码。代码是经过优化编译的（但有调试符号），所以事情可能会很混乱。

我的核心文件只是告诉我完全是胡说八道还是有办法让这有意义？

原文

My core file claims that a SIGFPE was thrown from

gcc-4.3.4/include/c++/4.3.4/bits/stl_iterator_base_funcs.h

on line 176. This is here:

  template<typename _InputIterator, typename _Distance>
    inline void
    advance(_InputIterator& __i, _Distance __n)
    {
          // concept requirements -- taken care of in __advance
176---->  typename iterator_traits<_InputIterator>::difference_type __d = __n;
          std::__advance(__i, __d, std::__iterator_category(__i));
    }

this is inside another function I have that is indeed calling advance surrounding by code that isn't doing any floating point arithmetic. The code is compiled with optimizations (but has debugging symbols), so things may be a big obfuscated.

Is my core file just telling me complete nonsense or is there a way this could make sense?

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等你爱我 2024-10-10 04:40:26

在回答我自己的问题时，优化器采用了如下所示的代码

int which = RANDOM % somecontainer.size();
std::advance(it, which);

并将它们组合起来。这就是为什么信号似乎是从 std::advance 内部发出的。根据 Oli 的评论，当您取相对于 0 的模数时，即使它不是浮点运算，也会发生 SIGFPE。还有一个不同的错误，它允许某些容器在极端情况下为空。

In answer to my own question, what happened is that optimizer took code that looked like this:

int which = RANDOM % somecontainer.size();
std::advance(it, which);

and combined them. This is why it appears the signal was raised from inside std::advance. Following Oli's comment, SIGFPE can occur when you take the modulus with respect to 0, even though it isn't a floating point operation. There was a different bug which allowed somecontainer to be empty in a corner case.

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