主结构体中次结构体含有柔性数组:分配空间和对最底层(含有柔性数组)结构体类似。
#include<stdio.h>
#include<stdlib.h>
struct mymsg1{
int len;
};
struct mymsg2{
char *cmdline;
};
struct mymsg3{
int len;
char *cmdline;
};
struct mymsg{
int len;
char cmdline[0];
};
struct msgreq{
struct mymsg my;
};
void setmsg(char * m)
{
char str[255] = "hello";
strncpy(m,str,strlen(str));
printf("%s\n",m);
}
/*int main(void)
{
struct msgreq *mreq;
char msg[255] = {'\0'};
setmsg(msg);
mreq = (struct msgreq*)malloc(sizeof(struct msgreq)+sizeof(char)*strlen(msg));
mreq->my.len = strlen(msg);
memcpy(mreq->my.cmdline,msg,mreq->my.len);
printf("%d,%d\n",(int)sizeof(mreq),(int)sizeof(struct msgreq));
printf("%s\n",mreq->my.cmdline);
free(mreq);
return 0;
}*/
int main()
{
printf(" 1: %d\n 2: %d\n 3: %d\n",(int)sizeof(struct mymsg1),(int)sizeof(struct mymsg2),(int)sizeof(struct mymsg3));
return 0;
}