英文:
When can the standard library functions throw exceptions?
问题
我有困难理解标准库中哪些函数可能会引发异常，以及在何种情况下可能会引发异常。
有些函数是noexcept，那么它们就不会引发异常，但是如果我查看例如std::string::operator[]()：https://en.cppreference.com/w/cpp/string/basic_string/operator_at，这个操作符并不是noexcept，但页面上没有提到异常（同样也是这里，所以这与std::basic_string是一个模板无关）。
我能否假设如果页面上没有列出异常，那么这个函数不会引发异常（但由于某些原因未被标记为noexcept）？或者是函数可能引发实现定义的异常？当列出异常时，它们是否是唯一可能引发的异常？
编辑：
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有人指出我应该参考实际的标准而不是cppreference来解决我的问题，并友好地提供了一个相关链接。
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在我的示例中，相关页面应该是这个：https://eel.is/c++draft/string.access，明确指出
operator[]()的Throws为Nothing。 -
话虽如此，在下面几行是
front()，它不是noexcept，并且在描述中没有Throws条目，所以我的问题仍然存在。
英文:
I'm having trouble understanding which functions from the standard library can throw exceptions, and if so which and when.
Some functions are noexcept, in which case ok they don't, but if I look for example at std::string::operator[](): https://en.cppreference.com/w/cpp/string/basic_string/operator_at, the operator is not noexcept yet the page says nothing about exceptions (and same here so it should have nothing to do with std::basic_string being a template).
Can I assume that if no exception is listed on a page then it means that the function cannot throw (but was not marked as noexcept for some reason)? Or does it mean the function can throw implementation-defined exceptions? And when exceptions are listed, are they the only ones that can be thrown?
Edit:
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Someone remarked that I should refer to the actual standard and not cppreference for my question, and kindly provided me a relevant link.
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In my example the relevant page would be this one: https://eel.is/c++draft/string.access which explicitly states
Throws: Nothingforoperator[]() -
That being said, a few lines below is
front(), which is notnoexceptand doesn't have aThrowsentry in its description, so my question still stands
答案1
得分: 1
有时候你必须看出字里行间。
字符串 operator[] 具有前提条件，索引必须有效。cppreference说：
> 如果 pos > size()，行为是未定义的。
未定义行为包括抛出异常。实际上，一些实现在调试模式下会抛出越界异常。
数学函数，如 std::abs，最初来自C库。尽管C库不会抛出异常，但它也不会为任何函数声明noexcept，为了保持兼容性，C++也不这样做。
英文:
Sometimes you have to read between the lines.
The string operator[] has a precondition that the index must be valid. cppreference says:
> If pos > size(), the behavior is undefined.
Undefined behavior includes throwing exceptions. And, in fact, some implementations will throw an out-of-range exception in debug mode.
The math functions, like std::abs, originally come from the C library. Even though the C library doesn't throw exceptions, it also doesn't say noexcept for any of the functions, so to be compatible neither does C++.
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