为什么短期存储为4个字节在C结构? [英] Why short is stored as 4 bytes in a struct in C?
问题描述
我有以下两个结构:
问题值是sizeof(内容)返回160.结构由11个短裤,6个整数,76个字符,7辆彩车,1双,共增加了158个字节。我已经算三次,还有2字节的区别。
The problem is the sizeof(Content) returns 160. The struct consists of 11 shorts, 6 ints, 76 chars, 7 floats, 1 double, totally adding to 158 bytes. I have counted three times and there is still a 2 byte difference.
typedef struct TIME_T {
short year,mon,day;
short hour,min,sec;
} TIME;
typedef struct {
int no;
char name[20];
char Code[10];
char DASType[10];
short wlen;
float VLtd;
int samp;
int comp;
int locationID;
short TranMode;
char TranIns[12];
short TimerMode;
char ClkType[12];
float ClkErr;
float lat;
float lon;
float alt;
float azimuth,incident;
short weight;
short veloc;
int oritype;
char seismometer[12];
double sens;
TIME start_time;
int record_samples;
} Content;
我写了一小块code的打印在结构中每个变量的位置,突然我发现浮法WLEN
需要4个字节。我的code是如下:
I write a small piece of code to print the position of each variables in the struct, and suddenly I find the float wlen
takes 4 bytes. My code is as follows:
int main(void)
{
Content content;
printf("Sizeof Content: %d\n", sizeof(content));
printf("Sizeof int content.no: %d\n", (int)&content.name - (int)&content.no);
printf("Sizeof char[20] content.name: %d\n", (int)&content.Code - (int)&content.name);
printf("Sizeof char[10] content.Code: %d\n", (int)&content.DASType - (int)&content.Code);
printf("Sizeof char[10] content.DASType: %d\n", (int)&content.wlen - (int)&content.DASType);
printf("Sizeof short content.wlen: %d\n", (int)&content.VLtd - (int)&content.wlen);
printf("Sizeof float content.VLtdL %d\n", (int)&content.samp - (int)&content.VLtd);
printf("Sizeof int content.samp: %d\n", (int)&content.comp - (int)&content.samp);
printf("Sizeof int content.comp: %d\n", (int)&content.locationID - (int)&content.comp);
printf("Sizeof int content.locationID: %d\n", (int)&content.TranMode - (int)&content.locationID);
printf("Sizeof short content.TranMode: %d\n", (int)&content.TranIns - (int)&content.TranMode);
printf("Sizeof char[12] content.TranIns: %d\n", (int)&content.TimerMode - (int)&content.TranIns);
printf("Sizeof short content.TimerMode: %d\n", (int)&content.ClkType - (int)&content.TimerMode);
printf("Sizeof char[12] content.ClkType: %d\n", (int)&content.ClkErr - (int)&content.ClkType);
printf("Sizeof float content.ClkErr: %d\n", (int)&content.lat - (int)&content.ClkErr);
printf("Sizeof float content.lat: %d\n", (int)&content.lon - (int)&content.lat);
printf("Sizeof floatcontent.lon: %d\n", (int)&content.alt - (int)&content.lon);
printf("Sizeof floatcontent.alt: %d\n", (int)&content.azimuth - (int)&content.alt);
printf("Sizeof floatcontent.azimuth: %d\n", (int)&content.incident - (int)&content.azimuth);
printf("Sizeof floatcontent.incident: %d\n", (int)&content.weight - (int)&content.incident);
printf("Sizeof short content.weight: %d\n", (int)&content.veloc - (int)&content.weight);
printf("Sizeof short content.veloc: %d\n", (int)&content.oritype - (int)&content.veloc);
printf("Sizeof int content.oritype: %d\n", (int)&content.seismometer - (int)&content.oritype);
printf("Sizeof char[12] content.seismometer: %d\n", (int)&content.sens - (int)&content.seismometer);
printf("Sizeof double content.sens: %d\n", (int)&content.start_time - (int)&content.sens);
printf("Sizeof TIME content.start_time: %d\n", (int)&content.record_samples - (int)&content.start_time);
printf("Sizeof int content.record_samples: %d\n", sizeof(content.record_samples));
getchar();
return 0;
}
的输出如下所示:
The output is as follows:
Sizeof int content.no: 4
Sizeof char[20] content.name: 20
Sizeof char[10] content.Code: 10
Sizeof char[10] content.DASType: 10
Sizeof short content.wlen: 4
**Sizeof float content.VLtdL 4**
Sizeof int content.samp: 4
Sizeof int content.comp: 4
Sizeof int content.locationID: 4
Sizeof short content.TranMode: 2
Sizeof char[12] content.TranIns: 12
Sizeof short content.TimerMode: 2
Sizeof char[12] content.ClkType: 12
Sizeof float content.ClkErr: 4
Sizeof float content.lat: 4
Sizeof floatcontent.lon: 4
Sizeof floatcontent.alt: 4
Sizeof floatcontent.azimuth: 4
Sizeof floatcontent.incident: 4
Sizeof short content.weight: 2
Sizeof short content.veloc: 2
Sizeof int content.oritype: 4
Sizeof char[12] content.seismometer: 12
Sizeof double content.sens: 8
Sizeof TIME content.start_time: 12
Sizeof int content.record_samples: 4
编译器是MSVC8,没有定义UNI code,定义没有其他的宏。这是86。
The compiler is MSVC8, no UNICODE defined, no other macro defined. It's x86.
我试图编译相同code在gcc版本3.4.4,输出是一样的。的sizeof短content.wlen:4
I tried to compile the same code in gcc version 3.4.4, the output is the same.
Sizeof short content.wlen: 4
谁能解释这样对我?
先谢谢了。
编辑:谢谢回答!我有现在。
Thanks for answering! I have got it now.
推荐答案
简短的回答只是:对准
这篇关于为什么短期存储为4个字节在C结构?的文章就介绍到这了,希望我们推荐的答案对大家有所帮助,也希望大家多多支持IT屋!