C程序代码的内存结构分析

程序内部的结构是分段的，一般分为代码段、堆、栈、数据段等。可以通过下面的代码来证明：

#include <stdio.h>

int globalIntA=10;

void variableInStack()
{
    printf("%s:%d:%s location is %p
",__FILE__,__LINE__,__FUNCTION__,(void*)&__FUNCTION__);
    printf("%s:%d:%s global globalIntA is %p
",__FILE__,__LINE__,__FUNCTION__,(void*)&globalIntA);
    int localIntB=100;
    printf("%s:%d:%s local localIntB is %p
",__FILE__,__LINE__,__FUNCTION__,(void*)&localIntB);
}

void variableInHeap()
{
    printf("%s:%d:%s location is %p
",__FILE__,__LINE__,__FUNCTION__,(void*)&__FUNCTION__);
    char *description = malloc(10* sizeof(char));
    if( description == NULL )
    {
        fprintf(stderr, "Error - unable to allocate required memory
");
    }
    else
    {
        strcpy( description, "IN HEAP");
    }
    printf("Description: %s
", description );

    printf("%s:%d:%s malloc description is %p
",__FILE__,__LINE__,__FUNCTION__,(void*)&description);
    printf("%s:%d:%s malloc *description is %p
",__FILE__,__LINE__,__FUNCTION__,&(*description));
    free((void*)description);
    int localIntB=100;
    printf("%s:%d:%s local localIntB is %p
",__FILE__,__LINE__,__FUNCTION__,(void*)&localIntB);
    static int stcIntC;
    printf("%s:%d:%s static int stcIntC is %p
",__FILE__,__LINE__,__FUNCTION__,(void*)&stcIntC);
}


int globalIntB;

int main(int argc, char ** argv)
{
    printf("%s:%d:%s process begin @ %p
",__FILE__,__LINE__,__FUNCTION__,(void*)&__FUNCTION__);
    printf("%s:%d:%s global globalIntB is %p
",__FILE__,__LINE__,__FUNCTION__,(void*)&globalIntB);
    printf("====================
");
    variableInStack();
    printf("====================
");
    variableInHeap();
    return EXIT_SUCCESS;
}

程序的执行结果如下：
/Users/huGuohua/xcode/c_study/c_study/main.c:30:main process begin @ 0x100003f5e
/Users/huGuohua/xcode/c_study/c_study/main.c:31:main global globalIntB is 0x10000810c
====================
/Users/huGuohua/xcode/c_study/c_study/memoryAddress.h:18:variableInStack location is 0x100003e04
/Users/huGuohua/xcode/c_study/c_study/memoryAddress.h:19:variableInStack global globalIntA is 0x1000080d8
/Users/huGuohua/xcode/c_study/c_study/memoryAddress.h:21:variableInStack local localIntB is 0x7ffeefbff42c
====================
/Users/huGuohua/xcode/c_study/c_study/memoryAddress.h:26:variableInHeap location is 0x100003e56
Description: IN HEAP
/Users/huGuohua/xcode/c_study/c_study/memoryAddress.h:38:variableInHeap malloc description is 0x7ffeefbff428
/Users/huGuohua/xcode/c_study/c_study/memoryAddress.h:39:variableInHeap malloc *description is 0x10181e6b0
/Users/huGuohua/xcode/c_study/c_study/memoryAddress.h:42:variableInHeap local localIntB is 0x7ffeefbff424
/Users/huGuohua/xcode/c_study/c_study/memoryAddress.h:44:variableInHeap static int stcIntC is 0x100008108
Program ended with exit code: 0

根据以上的结果，可以发现如下规律：
函数的地址在一起，放在代码段的；
函数内部的变量的地址在一起，放在栈段的；
全局变量放在数据段，数据段中还会存放静态变量；
如果一块内存是用malloc创建的，那么它在堆中；

这就是内存中的进程的几个段：
代码段存放可执行代码、字符串常量、常量数据；
数据段存放已初始化全局变量、静态变量；
栈存放局部变量、函数参数；
堆是用来动态内存分配的；