将fpos_t转换为int或char [英] Cast fpos_t to int or char

问题描述

我正在使用一个函数，该函数对文件的长度使用按位操作： fpos_t flen;

I'm working with a function that uses bitwise operations with the length of a file: fpos_t flen;

当我尝试将其转换为int或char，或尝试对其进行算术运算时，会失败并出现以下编译错误：
错误：在期望整数时使用的聚合值

When I try casting it to an int or char, or attempt on arithmetic operation on it, it fails with the following compilation error: error: aggregate value used where an integer was expected

推荐答案

您误用了该类型。首先，它不代表长度。它代表一个位置。其次，它只是用于调用 fsetpos 。你不是要对它进行算术，因为它不一定代表一个数字类型。它包含您的库需要能够执行 fsetpos 操作的任何信息。在你的库的实现中， fpos_t 似乎是一个聚合类型，例如一个struct。 （您可以检查头文件中的定义，但不要依赖于您在其中发现的任何内容;在其他平台或您的标准库的未来版本中它们会有所不同。）

You're misusing that type. First, it doesn't represent a length. It represents a position. Second, it's only meant to use in a call to fsetpos. You're not meant to do arithmetic on it because it doesn't necessarily represent a numeric type. It contains whatever information your library needs to be able to perform an fsetpos operation. In your library's implementation, fpos_t appears to be an aggregate type, such as a struct. (You can check the definition in the header files to be sure, but don't rely on whatever you discover there; it's liable to differ on other platforms or in future versions of your standard library.)

对于你的下一步，考虑问一个更直接的问题，如何解决你正在处理的任何问题，当你想出了在 fpos_t 。

As for your next step, consider asking a more direct question about how to solve whatever problem you were working on when you came up with the idea to do bitwise operations on a fpos_t.

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