不同类型数据存放位置简单分析

例子：

#include <stdio.h>
#include <stdlib.h>
#include <sys/types.h>
#include <unistd.h>
#include <fcntl.h>
#include <sys/shm.h>

#define ARRAY_SIZE 40000
#define MALLOC_SIZE 100000
#define SHM_SIZE 100000
#define SHM_MODE 0644

char array[ARRAY_SIZE];    //未初始化的数据,保存在未初始化数据段

char array2[ARRAY_SIZE]={1,2,3};    //初始化的数据，保存在初始化数据段


int main(void)
{
    int shmid;
    char *ptr,*shmptr;
    char array3[ARRAY_SIZE];

    printf("array[] from %x to %x\n",(unsigned)&array[0],(unsigned)&array[ARRAY_SIZE]);
    printf("array2[] from %x to %x\n",(unsigned)&array2[0],(unsigned)&array2[ARRAY_SIZE]);
    printf("array3[] from %x to %x\n",(unsigned)&array3[0],(unsigned)&array3[ARRAY_SIZE]);
    
    printf("stack around:shmid %x,ptr %x,shmptr %x\n",(unsigned)&shmid,(unsigned)&ptr,(unsigned)&shmptr);

    if((ptr=malloc(MALLOC_SIZE))==NULL)
    {
        perror("malloc");
        exit(-1);
    }
    printf("malloc from %x to %x\n",(unsigned)ptr,(unsigned)ptr+MALLOC_SIZE);

    if((shmid=shmget(IPC_PRIVATE,SHM_SIZE,SHM_MODE))<0)
    {
        perror("shmget");
        exit(-1);
    }
    if((shmptr=shmat(shmid,0,0))==(void *)-1)
    {
        perror("shmat");
        exit(-1);
    }
    printf("shared memory attached from %x to %x\n",(unsigned)shmptr,(unsigned)shmptr+SHM_SIZE);
    if(shmctl(shmid,IPC_RMID,0)<0)
    {
        perror("shmctl");
        exit(-1);
    }
    return 0;
}

运行结果：

array[] from 8053cc0 to 805d900
array2[] from 804a060 to 8053ca0
array3[] from bf82084c to bf82a48c
stack around:shmid bf820848,ptr bf820844,shmptr bf820840
malloc from 92ed008 to 93056a8
shared memory attached from b7895000 to b78ad6a0


由结果可以看出：
全局变量存放在数据段（初始化或非初始化数据段）；
普通局部变量在栈里；
malloc出的动态区域在堆中；
共享存储段紧靠在栈之下。

文件:	memory.c.tar.gz
大小:	0KB
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