为什么fgets接受int而不是size_t? [英] Why does fgets accept an int instead of a size_t?
问题描述
出于明显的原因，诸如strcpy()，malloc()，strlen()之类的函数以及其他各种函数都接受其参数或将返回值作为size_t而不是int或unsigned int来接收.
Functions such as strcpy(), malloc(), strlen() and various others accept their arguments or return values as a size_t instead of a int or an unsigned int for obvious reasons.
某些文件功能(例如fread()和fwrite())也使用size_t.通过扩展，可以预期char* fgets (char *str, int num, FILE *stream)应该使用size_t而不是int作为其缓冲区大小的参数.
Some file functions such as fread() and fwrite() use size_t as well. By extension, it would be expected that char* fgets (char *str, int num, FILE *stream) should use a size_t and not an int as argument for its buffer size.
但是， fgets() 使用int.为什么有任何客观的解释?
However, fgets() uses an int. Is there any objective explanation why?
推荐答案
原始K& R在p.155上使用int参数定义了fgets().书中介绍的代码本来可以工作
也使用unsigned int(它使用>0，但是编写了循环，所以永远不会低于零).
The original K&R defined fgets() on p.155 with an int argument. The code presented in the book would have worked
with an unsigned int as well (it uses a >0, but the loop is written so to never go below zero).
size_t稍后在 C89 (ANSI C)中作为sizeof()的类型进行介绍.由于此功能是专门为协调内存分配而引入的，因此内存
管理功能和字符串功能也进行了相应更新.但是文件I/O不是:在C89中唯一使用size_t的文件功能是那些新功能.
由C89引入并在K& R中不存在，例如fread()/fwrite().是的，K& R没有这些功能
并仅依靠使用文件描述符的(不可移植的)unix读/写功能进行块操作.
size_t got introduced later, in C89 (ANSI C), as the type of sizeof(). As this feature was specifically introduced for harmonizing memory allocation, memory
management functions and string functions were updated accordingly. But file I/O wasn't: the only file functions that used size_t in C89 are those new ones
introduced by C89 and did not exist in K&R such as for example fread()/fwrite(). Yes, K&R didn't have these functions
and relied for bloc operations only on (non portable) unix read/write functions using file descriptors.
应注意的是， POSIX标准已经统一了unix函数，与
ANSI C标准和于1988年末发布.该标准协调了许多使用size_t的unix函数，因此现在read()/write()
用size_t定义.但是对于C标准库功能(例如fgets())，POSIX优先于C标准
(标准当前版本的措词):
It shall be noted that the POSIX standard, which has harmonized the unix functions, was developed in parallel to
the ANSI C standard and issued late 1988. This standard has harmonized many unix functions to use size_t so that read()/write() nowadays
are defined with size_t. But for the C standard library functions such as fgets(), POSIX gives precedence to the C standard
(wording of the current version of the standard):
此参考页上描述的功能符合ISO C标准. 这里描述的要求与ISO C标准之间的任何冲突都是无意的.
The functionality described on this reference page is aligned with the ISO C standard. Any conflict between the requirements described here and the ISO C standard is unintentional.
因此，具有讽刺意味的是，在POSIX中，fgets()仍然继承自其历史K& R int.
So in POSIX also, ironically, fgets() still inherited from its historical K&R int.
其他阅读内容
additional reading
- 从K& R到Ansi C -多布博士(Dr.Dobb's)-1989年:
- Going from K&R to Ansi C - Dr.Dobb's - 1989:
stdio.h:此标头定义和原型化了K& R第7章中列出的大多数功能.几乎没有(如果有)更改 在K& R中可以找到一些定义，但已添加了几个新功能.
stdio.h: This header defines and prototypes most of the functions listed in Chapter 7 of K&R. Few, if any, changes were made in the definitions found in K&R but several new functions have been added.
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