C++中的和（C++基本数据类型的最值）

昨天有同学问到有关C++里具体数值的问题，看到还是有一点点懵的，想想网上应该能找到相关资料吧，后来发现挺少的，其实在mingw（编译文件）里可以找到limits.h这个文件，具体信息如下：

/*
 * 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: PATH_MAX is the POSIX equivalent for Microsoft's MAX_PATH; the two
 *       are semantically identical, with a limit of 259 characters for the
 *       path name, plus one for a terminating NUL, for a total of 260.
 */
#define PATH_MAX    260

/*
 * 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... */
#if ('\x80' < 0)
#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

#ifndef __STRICT_ANSI__
/* POSIX wants this.  */
#define SSIZE_MAX LONG_MAX
#endif

#if (defined (__STDC_VERSION__) && __STDC_VERSION__ >= 199901L) \
     || !defined(__STRICT_ANSI__)
/* ISO C9x macro names */
#define LLONG_MAX 9223372036854775807LL
#define LLONG_MIN (-LLONG_MAX - 1)
#define ULLONG_MAX (2ULL * LLONG_MAX + 1)
#endif

/*
 * The GNU C compiler also allows 'long long int'
 */
#if !defined(__STRICT_ANSI__) && defined(__GNUC__)

#define LONG_LONG_MAX   9223372036854775807LL
#define LONG_LONG_MIN   (-LONG_LONG_MAX-1)
#define ULONG_LONG_MAX  (2ULL * LONG_LONG_MAX + 1)

/* 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_ */

有了这头文件后就可以减少使用0x3fffffff这种类型了。