sizeof一些事

sizeof()返回一个变量或者类型大小（单位是字节）

struct rec //x64系统
{
    int* a; //8字节
    char b; //4字节，因为对齐
    int c;  //x64系统，4字节
};
sizeof(rec) = 16

// x64系统
char *a= "abcd\n";    //sizeof(a) =8
char b[10] ="abcd\n";  //sizeof(b) = 10
char c[][10] = {"aaa", "ccc"}; // sizeof(c)=20
char *d[10] = {"aaa", "ddd"}; //sizeof(d) = 80

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x86下各数据类型及指针大小（单位是字节）

Size of char is: 1

Size of unsigned char is: 1

Size of signed char is: 1

Size of int is: 4

Size of short is: 2

Size of long is: 4

Size of long int is: 4

Size of signed int is: 4

Size of unsigned int is: 4

Size of unsigned long int is: 4

Size of long long int is: 8

Size of unsigned long long is: 8

Size of float is: 4

Size of double is: 8

Size of long double is: 8

Size of (void *) is: 4

Size of (char *) is: 4

Size of (int *) is: 4

Size of (long *) is: 4

Size of (long long *) is: 4

Size of (float *) is: 4

Size of (double *) is: 4

所有指针都是占4字节

---

x64下各数据类型及指针大小（单位是字节）

Size of char is: 1

Size of unsigned char is: 1

Size of signed char is: 1

Size of int is: 4

Size of short is: 2

Size of long is: 8

Size of long int is: 8

Size of signed int is: 4

Size of unsigned int is: 4

Size of unsigned long int is: 8

Size of long long int is: 8

Size of unsigned long long is: 8

Size of float is: 4

Size of double is: 8

Size of long double is: 16

Size of (void *) is: 8

Size of (char *) is: 8

Size of (int *) is: 8

Size of (long *) is: 8

Size of (long long *) is: 8

Size of (float *) is: 8

Size of (double *) is: 8

所有指针都是占8字节