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研发客服# gcc -v
gcc version 4.4.5 (Ubuntu/Linaro 4.4.4-14ubuntu5)
重点:
代码中的内存分配, 地址从低到高: 代码段(RO, 保存函数代码) --> 只读数据段(RO, 保存常量) --> 数据段(RW, 已初始化并且初始值不为0的全局变量和静态变量) -->bss段(RW, 未初始化或者初始化为0的全局变量和静态变量).
程序运行起来之后, 堆区和栈区的变量地址是动态分配的.
#include
#include
int global_ni; // .bss
int global_iz = 0 ; // .bss
int global_inz = 1; // .data
const int global_const0 = 0;
const int global_const1 = 1;
void function(void)
{
int local_fni;
int local_finz = 1;
int local_fiz = 0 ;
static int static_fni;
static int static_finz = 1;
static int static_fiz = 0 ;
int *p2 = (int*)malloc(sizeof(int));
printf("子函数 局部变量 : n");
printf(" local_fni: %p n", &local_fni);
printf(" local_finz: %p n", &local_finz);
printf(" local_fiz: %p n", &local_fiz);
printf("子函数 静态变量 : n");
printf(" static_fni: %p n", &static_fni);
printf(" static_finz: %p n", &static_finz);
printf(" static_fiz: %p n", &static_fiz);
printf("子函数 指针变量 : n");
printf(" p2 : %p n", p2);
printf("子函数地址 : n");
printf(" function : %p n", function);
}
int main(int argc, char **argv)
{
int local_mni;
int local_minz = 1;
int local_miz = 0 ;
static int static_mni;
static int static_minz = 1;
static int static_miz = 0 ;
int *p1 = (int*)malloc(sizeof(int));
const int local_const0 = 0;
const int local_const1 = 1;
char* str_ptr = "char";
printf("主函数 局部变量 : n");
printf(" local_mni : %p n", &local_mni);
printf(" local_minz : %p n", &local_minz);
printf(" local_miz : %p n", &local_miz);
printf("const 变量: n");
printf(" local_const0 : %p n", &local_const0);
printf(" local_const1 : %p n", &local_const1);
printf(" global_const0 : %p n", &global_const0);
printf(" global_const1 : %p n", &global_const1);
printf("主函数 malloc指针变量 : n");
printf(" p1 : %p n", p1);
printf("全局变量 : n");
printf(" global_ni : %p n", &global_ni);
printf(" global_inz : %p n", &global_inz);
printf(" global_iz : %p n", &global_iz);
printf("主函数 静态变量 : n");
printf(" static_mni: %p n", &static_mni);
printf(" static_minz: %p n", &static_minz);
printf(" static_miz: %p n", &static_miz);
printf("字符串常量 : n");
printf(" str_ptr : %p n", str_ptr);
printf("主函数地址 : n");
printf(" main : %p n", main);
printf("= = = = = = = = = = = = = = = n");
function();
return 0;
}
/*
= = = = = = = = = = = = = = =
测试:
gcc -o test main.c
objdump -Dhs test > test.dis
./test
分析:
Disassembly of section .text: 08048370
{
子函数地址 :
function : 0x8048424
主函数地址 :
main : 0x804851d
}
Disassembly of section .rodata: 080487d8
{
const 变量: 全局
global_const0 : 0x80487e0
global_const1 : 0x80487e4
字符串常量 :
str_ptr : 0x80488d0
}
//.data中是初始化为非0的全局变量和静态变量
Disassembly of section .data: 0804a014
{
子函数 静态变量 :
static_finz: 0x804a024
全局变量 :
global_inz : 0x804a01c
主函数 静态变量 :
static_minz: 0x804a020
}
//.bss中是初始化为0以及没有初始化的全局变量和静态变量
Disassembly of section .bss: 0804a028
{
子函数 静态变量 :
static_fni: 0x804a03c
static_fiz: 0x804a040
全局变量 :
global_iz : 0x804a030
global_ni : 0x804a044
主函数 静态变量 :
static_mni: 0x804a034
static_miz: 0x804a038
}
堆空间: //动态的
{
主函数 malloc指针变量 :
p1 : 0x967c008
子函数 malloc指针变量 :
p2 : 0x967c018
}
栈空间: //动态的
{
子函数 局部变量 :
local_fiz : 0xbfb79924
local_finz: 0xbfb79928
local_fni : 0xbfb7992c
const 变量: 局部
local_const1 : 0xbfe3cee8
local_const0 : 0xbfe3ceec
主函数 局部变量 :
local_miz : 0xbfb79964
local_minz: 0xbfb79968
local_mni : 0xbfb7996c
}
*/
附反汇编文件test.dis节选
test: file format elf32-i386
Sections:
Idx Name Size VMA LMA File off Algn
0 .interp 00000013 08048134 08048134 00000134 2**0
CONTENTS, ALLOC, LOAD, READONLY, DATA
1 .note.ABI-tag 00000020 08048148 08048148 00000148 2**2
CONTENTS, ALLOC, LOAD, READONLY, DATA
2 .note.gnu.build-id 00000024 08048168 08048168 00000168 2**2
CONTENTS, ALLOC, LOAD, READONLY, DATA
3 .gnu.hash 00000020 0804818c 0804818c 0000018c 2**2
CONTENTS, ALLOC, LOAD, READONLY, DATA
4 .dynsym 00000070 080481ac 080481ac 000001ac 2**2
CONTENTS, ALLOC, LOAD, READONLY, DATA
5 .dynstr 00000058 0804821c 0804821c 0000021c 2**0
CONTENTS, ALLOC, LOAD, READONLY, DATA
6 .gnu.version 0000000e 08048274 08048274 00000274 2**1
CONTENTS, ALLOC, LOAD, READONLY, DATA
7 .gnu.version_r 00000020 08048284 08048284 00000284 2**2
CONTENTS, ALLOC, LOAD, READONLY, DATA
8 .rel.dyn 00000008 080482a4 080482a4 000002a4 2**2
CONTENTS, ALLOC, LOAD, READONLY, DATA
9 .rel.plt 00000028 080482ac 080482ac 000002ac 2**2
CONTENTS, ALLOC, LOAD, READONLY, DATA
10 .init 00000030 080482d4 080482d4 000002d4 2**2
CONTENTS, ALLOC, LOAD, READONLY, CODE
11 .plt 00000060 08048304 08048304 00000304 2**2
CONTENTS, ALLOC, LOAD, READONLY, CODE
12 .text 0000044c 08048370 08048370 00000370 2**4
CONTENTS, ALLOC, LOAD, READONLY, CODE
13 .fini 0000001c 080487bc 080487bc 000007bc 2**2
CONTENTS, ALLOC, LOAD, READONLY, CODE
14 .rodata 000002db 080487d8 080487d8 000007d8 2**2
CONTENTS, ALLOC, LOAD, READONLY, DATA
15 .eh_frame 00000004 08048ab4 08048ab4 00000ab4 2**2
CONTENTS, ALLOC, LOAD, READONLY, DATA
16 .ctors 00000008 08049f14 08049f14 00000f14 2**2
CONTENTS, ALLOC, LOAD, DATA
17 .dtors 00000008 08049f1c 08049f1c 00000f1c 2**2
CONTENTS, ALLOC, LOAD, DATA
18 .jcr 00000004 08049f24 08049f24 00000f24 2**2
CONTENTS, ALLOC, LOAD, DATA
19 .dynamic 000000c8 08049f28 08049f28 00000f28 2**2
CONTENTS, ALLOC, LOAD, DATA
20 .got 00000004 08049ff0 08049ff0 00000ff0 2**2
CONTENTS, ALLOC, LOAD, DATA
21 .got.plt 00000020 08049ff4 08049ff4 00000ff4 2**2
CONTENTS, ALLOC, LOAD, DATA
22 .data 00000014 0804a014 0804a014 00001014 2**2
CONTENTS, ALLOC, LOAD, DATA
23 .bss 00000020 0804a028 0804a028 00001028 2**2
ALLOC
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