gcc的__attribute__編譯屬性有很多子項，用於改變作用物件的特性。這裡討論section子項的作用。

__attribute__的section子項使用方式為：

__attribute__((section("section_name")))

看以下程式片段：

#include<unistd.h>
#include<stdint.h>
#include<stdio.h>

typedefvoid(*myown_call)(void);

extern myown_call _
 
myown_start;
extern myown_call _myown_end;

#define _init __attribute__((unused, section(".myown")))
#define func_init(func) myown_call _fn_##func _init = func

staticvoidmspec1(void){
        write(1, "aha!\n", 5);
}

staticvoidmspec2(void){
        write(1, "aloha!\n", 7);
}

staticvoidmspec3(void
 
){
        write(1, "hello!\n", 7);
}

func_init(mspec1);
func_init(mspec2);
func_init(mspec3);

/* exactly like below:
static myown_call mc1  __attribute__((unused, section(".myown"))) = mspec1;
static myown_call mc2  __attribute__((unused, section(".myown"))) = mspec2;
static myown_call mc3  __attribute__((unused, section(".myown"))) = mspec3;
*/
 


voiddo_initcalls(void){
        myown_call *call_ptr = &_myown_start;
        do {
                fprintf (stderr, "call_ptr: %p\n", call_ptr);
                (*call_ptr)();
                ++call_ptr;
        } while (call_ptr < &_myown_end);

}

intmain(void){
        do_initcalls();
        return 0;
}

兩個extern變數：

extern myown_call _myown_start;
extern myown_call _myown_end;

ld --verbose

__bss_start = .;

_myown_start = .;
  .myown           : { *(.myown) } = 0x90000000
  _myown_end = .;
  code_segment    : { *(code_segment) }

儲存修改後的連結器指令碼，假設程式為s.c，連結器指令碼儲存為s.lds，使用以下命令編譯：

gcc s.c -Wl,-Ts.lds

[[email protected] ]# ./a.out 
call_ptr: 0x8049768
aha!
call_ptr: 0x804976c
aloha!
call_ptr: 0x8049770
hello!

Have Fun!

其他參考：

http://blog.chinaunix.net/uid-27664726-id-4243961.html

http://www.cnblogs.com/lixiaofei1987/p/3198638.html