Some one got know how to write a lds(linker script) file?

Richard.Yang · 10-13-2010, 01:27 AM

Hi, all

I first found something called lds(linker script) file.

And now I am willing to do a test with __attribute__((section)) to make a function stay in a private section. Sounds fun to me.

Part of my source code looks like this
typedef struct A
{
int a;
}A;
A a __attribute__((section ("my_own")));

By objdump, I didn't find a section called "my_own".
So I guess the lds is needed. Anyone got some idea on this?
Or I approach is impossible?

paulsm4 · 10-13-2010, 01:46 AM

Hi -

Works fine for me. Specifically:

Code:

#include <stdio.h>

struct A
{
  int a, b;
};

struct A a __attribute ((section ("my_own")));

int
main (int argc, char *argv[])
{
  a.a = 1;
  a.b = 2;
  return 0;
}

Code:

gcc -c tmp.c

objdump -h tmp.o
tmp.o:     file format elf32-i386

Sections:
Idx Name          Size      VMA       LMA       File off  Algn
  0 .text         0000002d  00000000  00000000  00000034  2**2
                  CONTENTS, ALLOC, LOAD, RELOC, READONLY, CODE
  1 .data         00000000  00000000  00000000  00000064  2**2
                  CONTENTS, ALLOC, LOAD, DATA
  2 .bss          00000000  00000000  00000000  00000064  2**2
                  ALLOC
  3 my_own        00000008  00000000  00000000  00000064  2**2
                  CONTENTS, ALLOC, LOAD, DATA
  4 .comment      0000002e  00000000  00000000  0000006c  2**0
                  CONTENTS, READONLY
  5 .note.GNU-stack 00000000  00000000  00000000  0000009a  2**0
                  CONTENTS, READONLY

gcc --version
gcc (GCC) 4.1.2 20080704 (Red Hat 4.1.2-48)
Copyright (C) 2006 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

Richard.Yang · 10-14-2010, 02:30 AM

Thanks for you answer. I see this too.

BTW, I use
gcc tmp.c -o tmp
objdump -S tmp > tmp.s

In the tmp.s, I couldn't find a section called "my_own". Even the .bss and .data section.
Do you know the reason?