EOF的实际实现不同于-1 [英] Actual implementation of EOF different from -1

问题描述

POSIX 将EOF定义为宏扩展变为负值:

POSIX defines EOF as a macro expanding to a negative value:

标头应定义以下宏，该宏将扩展为类型为 int 且为负值的整数常量表达式:

The header shall define the following macro which shall expand to an integer constant expression with type int and a negative value:

EOF

文件结束返回值.

在每个实现中，我发现EOF总是定义为-1.

In every implementation I could find, EOF is always defined as -1.

尽管该标准允许使用不同的值，但我找不到发生这种情况的任何特定实现，因此我想为测试目的找到一个实现. ¹

Although the standard does allow for different values, I could not find any specific implementation where that happens, and I'd like to find one for testing purposes.¹

¹ 我可以自己实现，但我的真正目的是在野外找到它"，由于无法证明它的缺席，因此是次佳的选择我能想到的事情.

已经提出了几乎相同的问题，但是最后提出了两个问题，被接受的答案仅是答案第二个(大约WEOF).另一个用户回答否定中的第一个问题，但是由于该问题仅限于常见的C环境，否定性可以说是正确的: -1可能会用于任何明智的实现中具有小字符类型.

An almost identical question has already been asked, however there were two questions asked at the end, and the accepted answer only answers the second one (about WEOF). A different user replied to the first question in the negative, but because the question was restricted to common C environments, the negative is arguable correct: -1 is likely to be used in any sensible implementation with small char type.

由于我的问题是关于 existence 的，所以真正回答它的唯一方法是提供一个示例，所以我将其重新表述:请提供一个现有实现的示例，其中 .无论是newlib还是musl，PDP或VAX，Plan 9或Hurd，libc/硬件/操作系统与POSIX兼容或ISO C兼容的libc的任意组合都是有效的.

Since my question is about existence, the only way to actually answer it is to provide an example, so I will rephrase it: please provide an example of an existing implementation where EOF != -1. Be it newlib or musl, PDP or VAX, Plan 9 or Hurd, any combination of libc/hardware/operating system with a POSIX-compatible or ISO C-compatible libc where this happens is valid.

推荐答案

懒惰的星期日，所以我发现了这个 rel ="nofollow noreferrer"> https://github.com/xinu-os/xinu/blob/master/include/stddef.h 列出

Lazy Sunday, so I found this https://github.com/xinu-os/xinu which comes with this https://github.com/xinu-os/xinu/blob/master/include/stddef.h listing this

#define EOF (-2) /**< End-of-file (usually from read)    */

:-)

可追溯到1987年的Xinu来源在这里: https://www.tuhs.org//cgi-bin/utree.pl?file=Xinu7 ，不幸的是，它似乎将-1用作EOF的值. :-(

Xinu sources dated back to 1987 are here: https://www.tuhs.org//cgi-bin/utree.pl?file=Xinu7 which unfortunately seem to be using -1 as value for EOF. :-(

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