limits.h

用于检测整型数据数据类型的表达值范围

limits.h，计算机科学术语，指专门用于检测整型数据数据类型的表达值范围。

基本释义

limits.h包含内容（包括注释）

* limits.h

* This file has no copyright assigned and is placed in the Public Domain.

* This file is a part of the mingw-runtime package.

* No warranty is given; refer to the file DISCLAIMER within the package.

* Functions for manipulating paths and directories (included from io.h)

* plus functions for setting the current drive.

* Defines constants for the sizes of integral types.

* NOTE: GCC should supply a version of this header and it should be safe to

* use that version instead of this one (maybe safer).

#ifndef _LIMITS_H_

#define _LIMITS_H_

/* All the headers include this file. */

#include <_mingw.h>

* File system limits

* TODO: NAME_MAX and OPEN_MAX are file system limits or not? Are they the

* same as FILENAME_MAX and FOPEN_MAX from stdio.h?

* NOTE: Apparently the actual size of PATH_MAX is 260, but a space is

* required for the NUL. TODO: Test?

#define PATH_MAX (259)

* Characteristics of the char data type.

* TODO: Is MB_LEN_MAX correct?

#define CHAR_BIT 8

#define MB_LEN_MAX 2

#define SCHAR_MIN (-128)

#define SCHAR_MAX 127

#define UCHAR_MAX 255

/* TODO: Is this safe? I think it might just be testing the preprocessor,

* not the compiler itself... */

#define CHAR_MIN SCHAR_MIN

#define CHAR_MAX SCHAR_MAX

#else

#define CHAR_MIN 0

#define CHAR_MAX UCHAR_MAX

#endif

* Maximum and minimum values for ints.

#define INT_MAX 2147483647

#define INT_MIN (-INT_MAX-1)

#define UINT_MAX 0xffffffff

* Maximum and minimum values for shorts.

#define SHRT_MAX 32767

#define SHRT_MIN (-SHRT_MAX-1)

#define USHRT_MAX 0xffff

* Maximum and minimum values for longs and unsigned longs.

* TODO: This is not correct for Alphas, which have 64 bit longs.

#define LONG_MAX 2147483647L

#define LONG_MIN (-LONG_MAX-1)

#define ULONG_MAX 0xffffffffUL

* The GNU C compiler also allows 'long long int'

#if !defined(__STRICT_ANSI__) && defined(__GNUC__)

#define LONG_LONG_MAX 9223370L

#define LONG_LONG_MIN (-LONG_LONG_MAX-1)

#define ULONG_LONG_MAX (2ULL * LONG_LONG_MAX + 1)

/* ISO C9x macro names */

#define LLONG_MAX LONG_LONG_MAX

#define LLONG_MIN LONG_LONG_MIN

#define ULLONG_MAX ULONG_LONG_MAX

/* MSVC compatibility */

#define _I64_MIN LONG_LONG_MIN

#define _I64_MAX LONG_LONG_MAX

#define _UI64_MAX ULONG_LONG_MAX

#endif /* Not Strict ANSI and GNU C compiler */

#endif /* not _LIMITS_H_ */

补充内容

要判断某种特定类型可以容纳的最大值或最小值，一种简便的方法是使用ANSI标准头文件limits.h中的预定义值。该文件包含一些很有用的常量，它们定义了各种类型所能容纳的值，下表列出了这些常量：

常量描述

CHAR_BIT char的二进制位数(bit)

CHAR_MAX char的有符号整数最大值

CHAR_MIN char的有符号整数最小值

MB_LEN_MAX 多字节字符的最大字节(byte)数

INT_MAX int的有符号最大值

INT_MIN int的有符号最小值

LONG_MAX long的十进制最大值

LONG_MIN long的十进制最小值

SCHAR_MAX signedchar的十进制整数最大值

SCHAR_MIN signedchar的十进制整数最小值

SHRT_MIN short的十进制最小值

SHRT_MAX short的十进制最大值

UCHAR_MAX unsignedchar的十进制整数最大值

UINT_MAX unsignedint的十进制最大值

ULONG_MAX unsignedlongint的十进制最大值

USHRT_MAX unsignedshortint的十进制最大值

对于整数类型，在使用2的补码运算的机器(你将使用的机器几乎都属此类)上，一个有符号类型可以容纳的数字范围为[- 2^(位数-1) ]到[+ 2^(位数 -1)-1]，一个无符号类型可以容纳的数字范围为0到(+ 2^位数 )。例如，一个16位有符号整数可以容纳的数字范围为-2^15(即-32768)到(+2^15-1)(即+32767)。而16为无符号整数可容纳的最大值为(2^位数-1)或表示为汇编形式0xffff。

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