Question

我的系统是Linux x86_64。 INT数据类型的最大值显示为2147483648（使用标头）而不是32767（与16位int的情况一样）。为什么呢？

Answer 1

除非您自己定义，否则没有类型INT。该类型称为int。 C区分大小写。

C标准表示int类型的对象具有执行环境体系结构所建议的自然大小“。对于64位系统，这确实意味着INT_MAX应该是2 ⁶³ -1 - 但这不是一个硬性要求。

要求是int必须至少为16位宽，并且必须至少与short一样宽且不宽于long。（POSIX要求int至少为32位。）

为系统支持的所有大小提供整数类型很有用。特别是，在大多数现代系统中，预定义的大小为8,16,32和64位的整数类型很有用。

char通常为8位。如果我们使int为64位，则short为16位且我们没有32位类型，或short为32位且我们没有16位类型。（我还研究过没有16位或 32位整数类型的系统。）

编译器可以通过定义自己的扩展整数类型来解决这个问题，但编译器通常不会这样做。

实际上，在64位系统上制作int 32位并不是一个真正的问题。对32位整数的操作是有效的，如果需要64位整数，可以使用long中定义的long long，int64_t或<stdint.h>。（实际上，64位Windows将long定义为32位，但long long始终至少为64位。）

结论：C标准允许在定义int方面具有相当大的灵活性，编译器实现者以他们认为最方便用户的方式定义它。与为32位系统编写的代码的兼容性通常是主要考虑因素。

Answer 2

不保证各种整数类型的大小。你唯一可以指望的是：

sizeof(long long) >= sizeof(long) >= sizeof(int) >= sizeof(short) >= sizeof(char) == 1

那就是说，在现今的大多数实际系统中，你有：

sizeof(long long) == 8
sizeof(long)      == 8 or 4, depending on the architecture and compiler
sizeof(int)       == 4
sizeof(short)     == 2
sizeof(char)      == 1

int很长一段时间没有16位。它很少是64位。除了在MSVC上，通常long与体系结构的大小相同。

您还可以使用INT_MIN / INT_MAX和limits.h中的类似常量获取其最小值/最大值。

Answer 3

因为32位可以表示0到2147483647之间的整数值，16位可以表示0到32767.

您的系统似乎sizeof(int) = 4 bytes INT_MAX = 2147483647

PS：sizeof(int)因平台而异。

Answer 4

标准定义的int最小为16位。 2^31 = 2147483648（遗漏了符号位），因此您的实现具有比最低要求更大的int。

int甚至可以是更大的类型，因为标准只定义了与其他整数类型的最小长度和相对大小。

Answer 5

int的最小宽度按标准定义为16位，但现在这种情况并不常见。

相反，32位int很常见，您的平台似乎也是如此，因此INT_MAX可能是2147483647。

Answer 6

我刚刚在Linux Debian x64上编译了该程序：

#include <stdio.h>

int main(){

// C18 standard, p. 20

    printf("\n\n***********************************************************************************\n\n");

    printf ("%-25s %20s %20s %15s\n\n", "", "IZVORNA KODA", "BINARNA KODA", "OPOMBA");

    signed char n009 = 255;
    printf ("%-25s %20s %20d %15s\n","signed char:", "255", n009, "!");

    signed char n007 = 128;
    printf ("%-25s %20s %20d %15s\n","signed char:", "128", n007, "!");

    signed char n006 = 127;
    printf ("%-25s %20s %20d %15s\n","signed char:", "127", n006, "MAX - C18");

    signed char n005 = 1;
    printf ("%-25s %20s %20d %15s\n","signed char:", "1", n005, "C18");

    signed char n004 = 0;
    printf ("%-25s %20s %20d %15s\n","signed char:", "0",  n004, "C18");

    signed char n003 = -1;
    printf ("%-25s %20s %20d %15s\n", "signed char:", "-1", n003, "C18");

    signed char n002 = -127;
    printf ("%-25s %20s %20d %15s\n", "signed char", "-127", n002, "C18");

    signed char n001 = -128;    
    printf ("%-25s %20s %20d %15s\n", "signed char", "-128", n001, "MIN - C18");

    printf("\nALOKACIJA: %d bitov",sizeof(n009)*8);

    printf("\n\n***********************************************************************************\n\n");

    printf ("%-25s %20s %20s %15s\n\n", "", "IZVORNA KODA", "BINARNA KODA", "OPOMBA");

    unsigned char n017 = 255;
    printf ("%-25s %20s %20d %15s\n","unsigned char:", "255", n017, "MAX - C18");

    unsigned char n016 = 128;
    printf ("%-25s %20s %20d %15s\n","unsigned char:", "128", n016, "C18");

    unsigned char n015 = 127;
    printf ("%-25s %20s %20d %15s\n","unsigned char:", "127", n015, "C18");

    unsigned char n014 = 1;
    printf ("%-25s %20s %20d %15s\n","unsigned char:", "1", n014, "C18");

    unsigned char n013 = 0;
    printf ("%-25s %20s %20d %15s\n","unsigned char:", "0", n013, "MIN - C18");

    unsigned char n012 = -1;
    printf ("%-25s %20s %20d %15s\n","unsigned char:", "-1", n012, "!");

    unsigned char n011 = -127;
    printf ("%-25s %20s %20d %15s\n","unsigned char:", "-127", n011, "!");

    unsigned char n010 = -128;
    printf ("%-25s %20s %20d %15s\n","unsigned char:", "-128", n010, "!");

    printf("\nALOKACIJA: %d bitov",sizeof(n010)*8);

    printf("\n\n***********************************************************************************\n\n");

    short int n018 = 65535;
    printf ("%-25s %20s %20d %15s\n","short int:", "65535", n018, "!");

    short int n019 = 32768;
    printf ("%-25s %20s %20d %15s\n","short int:", "32768", n019, "!");

    short int n020 = 32767;
    printf ("%-25s %20s %20d %15s\n","short int:", "32767", n020, "MAX - C18");

    short int n021 = 32766;
    printf ("%-25s %20s %20d %15s\n","short int:", "32766", n021, "C18");

    short int n022 = 1;
    printf ("%-25s %20s %20d %15s\n","short int:", "1", n022, "C18");

    short int n023 = 0;
    printf ("%-25s %20s %20d %15s\n","short int:", "0", n023, "C18");

    short int n024 = -1;
    printf ("%-25s %20s %20d %15s\n","short int:", "-1", n024, "C18");

    short int n025 = -32767;
    printf ("%-25s %20s %20d %15s\n","short int:", "-32767", n025, "C18");

    short int n026 = -32768;
    printf ("%-25s %20s %20d %15s\n","short int:", "-32768", n026, "MIN - C18");

    printf("\nALOKACIJA: %d bitov",sizeof(n026)*8);

    printf("\n\n***********************************************************************************\n\n");

    unsigned short int n027 = 65535;
    printf ("%-25s %20s %20d %15s\n","unsigned short int:", "65535", n027, "MAX - C18");

    unsigned short int n028 = 32768;
    printf ("%-25s %20s %20d %15s\n","unsigned short int:", "32768", n028, "C18");

    unsigned short int n029 = 32767;
    printf ("%-25s %20s %20d %15s\n","unsigned short int:", "32767", n029, "C18");

    unsigned short int n030 = 32766;
    printf ("%-25s %20s %20d %15s\n","unsigned short int:", "32766", n030, "C18");

    unsigned short int n031 = 1;
    printf ("%-25s %20s %20d %15s\n","unsigned short int:", "1", n031, "C18");

    unsigned short int n032 = 0;
    printf ("%-25s %20s %20d %15s\n","unsigned short int:", "0", n032, "MIN - C18");

    unsigned short int n033 = -1;
    printf ("%-25s %20s %20d %15s\n","unsigned short int:", "-1", n033, "!");

    unsigned short int n034 = -32767;
    printf ("%-25s %20s %20d %15s\n","unsigned short int:", "-32767", n034, "!");

    unsigned short int n035 = -32768;
    printf ("%-25s %20s %20d %15s\n","unsigned short int:", "-32768", n035, "!");

    printf("\nALOKACIJA: %d bitov",sizeof(n035)*8);

    printf("\n\n***********************************************************************************\n\n");

    int n036 = 4294967295;
    printf ("%-25s %20s %20d %15s\n","int:", "4294967295", n036, "!");

    int n037 = 2147483648;
    printf ("%-25s %20s %20d %15s\n","int:", "2147483648", n037, "!");

    int n038 = 2147483647;
    printf ("%-25s %20s %20d %15s\n","int:", "2147483647", n038, "MAX - C18");

    int n039 = 1;
    printf ("%-25s %20s %20d %15s\n","int:", "1", n039, "C18");

    int n040 = 0;
    printf ("%-25s %20s %20d %15s\n","int:", "0", n040, "C18");

    int n041 = -1;
    printf ("%-25s %20s %20d %15s\n","int:", "-1", n041, "C18");

    int n042 = -2147483647;
    printf ("%-25s %20s %20d %15s\n","int:", "-2147483647", n042, "C18");

    int nnnm = -2147483648;
    printf ("%-25s %20s %20d %15s\n","int:", "-2147483648", nnnm, "MIN - C18");

    printf("\nALOKACIJA: %d bitov",sizeof(n042)*8);

    printf("\n\n***********************************************************************************\n\n");

    unsigned int n043 = 4294967295;
    printf ("%-25s %20s %20d %15s\n","unsigned int:", "4294967295", n043, "!");

    unsigned int n044 = 4294967294;
    printf ("%-25s %20s %20d %15s\n","unsigned int:", "4294967294", n044, "!");

    unsigned int n045 = 2147483648;
    printf ("%-25s %20s %20d %15s\n","unsigned int:", "2147483648", n045, "!");

    unsigned int n046 = 2147483647;
    printf ("%-25s %20s %20d %15s\n","unsigned int:", "2147483647", n046, "MAX - C18");

    unsigned int n047 = 1;
    printf ("%-25s %20s %20d %15s\n","unsigned int:", "1", n047, "C18");

    unsigned int n048 = 0;
    printf ("%-25s %20s %20d %15s\n","unsigned int:", "0", n048, "MIN - C18");

    unsigned int n049 = -1;
    printf ("%-25s %20s %20d %15s\n","unsigned int:", "-1", n049, "?");

    unsigned int n05d = -2147483647;
    printf ("%-25s %20s %20d %15s\n","unsigned int:", "-2147483647", n05d, "?");

    unsigned int n050 = -2147483648;
    printf ("%-25s %20s %20d %15s\n","unsigned int:", "-2147483648", n050, "?");

    printf("\nALOKACIJA: %d bitov",sizeof(n050)*8);

    printf("\n\n***********************************************************************************\n\n");

    long int n051 = 9223372036854775807;
    printf ("%-25s %20s %20d %15s\n","long int:", "9223372036854775807", n051, "!");

    long int n052 = 4294967294;
    printf ("%-25s %20s %20d %15s\n","long int:", "4294967294", n052, "!");

    long int n053 = 2147483648;
    printf ("%-25s %20s %20d %15s\n","long int:", "2147483648", n053, "!");

    long int n054 = 2147483647;
    printf ("%-25s %20s %20d %15s\n","long int:", "2147483647", n054, "MAX - C18");

    long int n055 = 1;
    printf ("%-25s %20s %20d %15s\n","long int:", "1", n055, "C18");

    long int n056 = 0;
    printf ("%-25s %20s %20d %15s\n","long int:", "0", n056, "C18");

    long int n057 = -1;
    printf ("%-25s %20s %20d %15s\n","long int:", "-1", n057, "C18");

    long int naaa = -2147483647;
    printf ("%-25s %20s %20d %15s\n","long int:", "-2147483647", naaa, "MIN - C18");

    long int n058 = -2147483648;
    printf ("%-25s %20s %20d %15s\n","long int:", "-2147483648", n058, "?");

    long int nnnn = -2147483649;
    printf ("%-25s %20s %20d %15s\n","long int:", "-2147483649", nnnn, "!");

    long int nbbb = -4294967294;
    printf ("%-25s %20s %20d %15s\n","long int:", "-4294967294", nbbb, "!");

    long int nccc = -9223372036854775807;
    printf ("%-25s %20s %20d %15s\n","long int:", "-9223372036854775807", nccc, "!");

    printf("\nALOKACIJA: %d bitov",sizeof(n057)*8);


    printf("\n\n***********************************************************************************\n\n");

    unsigned long int n059 = 9223372036854775807;
    printf ("%-25s %20s %20d %15s\n","unsigned long int:", "9223372036854775807", n059, "!");

    unsigned long int n060 = 4294967294;
    printf ("%-25s %20s %20d %15s\n","unsigned long int:", "4294967294", n060, "!");

    unsigned long int n061 = 2147483648;
    printf ("%-25s %20s %20d %15s\n","unsigned long int:", "2147483648", n061, "!");

    unsigned long int n062 = 2147483647;
    printf ("%-25s %20s %20d %15s\n","unsigned long int:", "2147483647", n062, "MAX - C18");

    unsigned long int n063 = 1;
    printf ("%-25s %20s %20d %15s\n","unsigned long int:", "1", n063, "C18");

    unsigned long int n064 = 0;
    printf ("%-25s %20s %20d %15s\n","unsigned long int:", "0", n064, "MIN - C18");

    unsigned long int n065 = -1;
    printf ("%-25s %20s %20d %15s\n","unsigned long int:", "-1", n065, "?");

    unsigned long int n066 = -2147483648;
    printf ("%-25s %20s %20d %15s\n","unsigned long int:", "-2147483648", n066, "?");

    unsigned long int nzzz = -4294967294;
    printf ("%-25s %20s %20d %15s\n","unsigned long int:", "-4294967294", nzzz, "!");

    unsigned long int nggg = -9223372036854775807;
    printf ("%-25s %20s %20d %15s\n","unsigned long int:", "-9223372036854775807", nggg, "!");

    printf("\nALOKACIJA: %d bitov",sizeof(n064)*8);

    printf("\n\n***********************************************************************************\n\n");

    long long int n080 = 9223372036854775807;
    printf ("%-25s %20s %20d %15s\n","long long int:", "9223372036854775807", n080, "!");

    long long int n081 = 4294967294;
    printf ("%-25s %20s %20d %15s\n","long long int:", "4294967294", n081, "!");

    long long int n082 = 2147483648;
    printf ("%-25s %20s %20d %15s\n","long long int:", "2147483648", n082, "!");

    long long int n083 = 2147483647;
    printf ("%-25s %20s %20d %15s\n","long long int:", "2147483647", n083, "MAX - C18");

    long long int n084 = 1;
    printf ("%-25s %20s %20d %15s\n","long long int:", "1", n084, "C18");

    long long int n085 = 0;
    printf ("%-25s %20s %20d %15s\n","long long int:", "0", n085, "MIN - C18");

    long long int n086 = -1;
    printf ("%-25s %20s %20d %15s\n","long long int:", "-1", n086, "?");

    long long int n087 = -2147483648;
    printf ("%-25s %20s %20d %15s\n","long long int:", "-2147483648", n087, "?");

    long long int n088 = -4294967294;
    printf ("%-25s %20s %20d %15s\n","long long int:", "-4294967294", n088, "!");

    long long int n089 = -9223372036854775807;
    printf ("%-25s %20s %20d %15s\n","long long int:", "-9223372036854775807", n089, "!");

    printf("\nALOKACIJA: %d bitov",sizeof(n089)*8);

    printf("\n\n***********************************************************************************\n\n");

    unsigned long long int n067 = 9223372036854775807;
    printf ("%-25s %20s %20d %15s\n","unsigned long long int:", "9223372036854775807", n067, "!");

    unsigned long long int n068 = 4294967294;
    printf ("%-25s %20s %20d %15s\n","unsigned long long int:", "4294967294", n068, "!");

    unsigned long long int n069 = 2147483648;
    printf ("%-25s %20s %20d %15s\n","unsigned long long int:", "2147483648", n069, "!");

    unsigned long long int n070 = 2147483647;
    printf ("%-25s %20s %20d %15s\n","unsigned long long int:", "2147483647", n070, "MAX - C18");

    unsigned long long int n071 = 1;
    printf ("%-25s %20s %20d %15s\n","unsigned long long int:", "1", n071, "C18");

    unsigned long long int n072 = 0;
    printf ("%-25s %20s %20d %15s\n","unsigned long long int:", "0", n072, "MIN - C18");

    unsigned long long int n073 = -1;
    printf ("%-25s %20s %20d %15s\n","unsigned long long int:", "-1", n073, "?");

    unsigned long long int n074 = -2147483648;
    printf ("%-25s %20s %20d %15s\n","unsigned long long int:", "-2147483648", n074, "?");

    unsigned long long int n075 = -4294967294;
    printf ("%-25s %20s %20d %15s\n","unsigned long long int:", "-4294967294", n075, "!");

    unsigned long long int n076 = -9223372036854775807;
    printf ("%-25s %20s %20d %15s\n","unsigned long long int:", "-9223372036854775807", n076, "!");

    printf("\nALOKACIJA: %d bitov",sizeof(n076)*8);

    return 0;
}

我使用了最新的标准C18进行了编译：

gcc -std=c18 -o 001 001.c

运行二进制文件后，我立即得到以下输出：

***********************************************************************************

                                  IZVORNA KODA         BINARNA KODA          OPOMBA

signed char:                               255                   -1               !
signed char:                               128                 -128               !
signed char:                               127                  127       MAX - C18
signed char:                                 1                    1             C18
signed char:                                 0                    0             C18
signed char:                                -1                   -1             C18
signed char                               -127                 -127             C18
signed char                               -128                 -128       MIN - C18

ALOKACIJA: 8 bitov

***********************************************************************************

                                  IZVORNA KODA         BINARNA KODA          OPOMBA

unsigned char:                             255                  255       MAX - C18
unsigned char:                             128                  128             C18
unsigned char:                             127                  127             C18
unsigned char:                               1                    1             C18
unsigned char:                               0                    0       MIN - C18
unsigned char:                              -1                  255               !
unsigned char:                            -127                  129               !
unsigned char:                            -128                  128               !

ALOKACIJA: 8 bitov

***********************************************************************************

short int:                               65535                   -1               !
short int:                               32768               -32768               !
short int:                               32767                32767       MAX - C18
short int:                               32766                32766             C18
short int:                                   1                    1             C18
short int:                                   0                    0             C18
short int:                                  -1                   -1             C18
short int:                              -32767               -32767             C18
short int:                              -32768               -32768       MIN - C18

ALOKACIJA: 16 bitov

***********************************************************************************

unsigned short int:                      65535                65535       MAX - C18
unsigned short int:                      32768                32768             C18
unsigned short int:                      32767                32767             C18
unsigned short int:                      32766                32766             C18
unsigned short int:                          1                    1             C18
unsigned short int:                          0                    0       MIN - C18
unsigned short int:                         -1                65535               !
unsigned short int:                     -32767                32769               !
unsigned short int:                     -32768                32768               !

ALOKACIJA: 16 bitov

***********************************************************************************

int:                                4294967295                   -1               !
int:                                2147483648          -2147483648               !
int:                                2147483647           2147483647       MAX - C18
int:                                         1                    1             C18
int:                                         0                    0             C18
int:                                        -1                   -1             C18
int:                               -2147483647          -2147483647             C18
int:                               -2147483648          -2147483648       MIN - C18

ALOKACIJA: 32 bitov

***********************************************************************************

unsigned int:                       4294967295                   -1               !
unsigned int:                       4294967294                   -2               !
unsigned int:                       2147483648          -2147483648               !
unsigned int:                       2147483647           2147483647       MAX - C18
unsigned int:                                1                    1             C18
unsigned int:                                0                    0       MIN - C18
unsigned int:                               -1                   -1               ?
unsigned int:                      -2147483647          -2147483647               ?
unsigned int:                      -2147483648          -2147483648               ?

ALOKACIJA: 32 bitov

***********************************************************************************

long int:                  9223372036854775807                   -1               !
long int:                           4294967294                   -2               !
long int:                           2147483648          -2147483648               !
long int:                           2147483647           2147483647       MAX - C18
long int:                                    1                    1             C18
long int:                                    0                    0             C18
long int:                                   -1                   -1             C18
long int:                          -2147483647          -2147483647       MIN - C18
long int:                          -2147483648          -2147483648               ?
long int:                          -2147483649           2147483647               !
long int:                          -4294967294                    2               !
long int:                 -9223372036854775807                    1               !

ALOKACIJA: 64 bitov

***********************************************************************************

unsigned long int:         9223372036854775807                   -1               !
unsigned long int:                  4294967294                   -2               !
unsigned long int:                  2147483648          -2147483648               !
unsigned long int:                  2147483647           2147483647       MAX - C18
unsigned long int:                           1                    1             C18
unsigned long int:                           0                    0       MIN - C18
unsigned long int:                          -1                   -1               ?
unsigned long int:                 -2147483648          -2147483648               ?
unsigned long int:                 -4294967294                    2               !
unsigned long int:        -9223372036854775807                    1               !

ALOKACIJA: 64 bitov

***********************************************************************************

long long int:             9223372036854775807                   -1               !
long long int:                      4294967294                   -2               !
long long int:                      2147483648          -2147483648               !
long long int:                      2147483647           2147483647       MAX - C18
long long int:                               1                    1             C18
long long int:                               0                    0       MIN - C18
long long int:                              -1                   -1               ?
long long int:                     -2147483648          -2147483648               ?
long long int:                     -4294967294                    2               !
long long int:            -9223372036854775807                    1               !

ALOKACIJA: 64 bitov

***********************************************************************************

unsigned long long int:    9223372036854775807                   -1               !
unsigned long long int:             4294967294                   -2               !
unsigned long long int:             2147483648          -2147483648               !
unsigned long long int:             2147483647           2147483647       MAX - C18
unsigned long long int:                      1                    1             C18
unsigned long long int:                      0                    0       MIN - C18
unsigned long long int:                     -1                   -1               ?
unsigned long long int:            -2147483648          -2147483648               ?
unsigned long long int:            -4294967294                    2               !
unsigned long long int:   -9223372036854775807                    1               !

一切正常，直到unsigned int，long int，unsigned long int，long long int和unsigned long long int都一样，有的甚至违反了标准（！），在第20页上明确定义了最大值和最小值：

因此很明显（a）GCC工具链存在问题，并且（b）您应避免使用int，这是C编程语言的灾难，因此这就是标准C11提出{ {1}}定义了新的整数数据类型：

int8_t
int16_t
int32_t
uint8_t
uint16_t
uint32_t
int64_t
uint64_t

和每个专业编程人员都在使用新的数据类型，其中保留了旧的数据类型以与较旧的软件兼容，但应避免使用。

也请注意在线课程。如果他们使用旧的数据类型，那么他们显然不了解C，因此您应该避免这些教训。

64位计算机中INT的最大值

6 个答案: