Merry Christmas Phil,
If the standard libraries are linked statically with a Linux C
program, why the whole library is not linked with our program? I saw
the final object code, it is not big, it probably shows that the
definition of some functions have been added to my program.
When i link some other libraries the whole functions of that library
are added completely but for the standard library only a few functions
are added?!! How?
My prog1.c is a simple printf:
------------------------------------------
main(){
printf("kkkkkkkk\n");
}
------------------------------------------
objdump -d ./prog1
./prog1: file format elf32-i386
Disassembly of section .init:
08048290 <_init>:
8048290: 55 push %ebp
8048291: 89 e5 mov %esp,%ebp
8048293: 53 push %ebx
8048294: 83 ec 04 sub $0x4,%esp
8048297: e8 00 00 00 00 call 804829c <_init+0xc>
804829c: 5b pop %ebx
804829d: 81 c3 68 13 00 00 add $0x1368,%ebx
80482a3: 8b 93 fc ff ff ff mov -0x4(%ebx),%edx
80482a9: 85 d2 test %edx,%edx
80482ab: 74 05 je 80482b2 <_init+0x22>
80482ad: e8 1e 00 00 00 call 80482d0 <__gmon_start__@plt>
80482b2: e8 d9 00 00 00 call 8048390 <frame_dummy>
80482b7: e8 84 01 00 00 call 8048440 <__do_global_ctors_aux>
80482bc: 58 pop %eax
80482bd: 5b pop %ebx
80482be: c9 leave
80482bf: c3 ret
Disassembly of section .plt:
080482c0 <__gmon_start__@plt-0x10>:
80482c0: ff 35 08 96 04 08 pushl 0x8049608
80482c6: ff 25 0c 96 04 08 jmp *0x804960c
80482cc: 00 00 add %al,(%eax)
...
080482d0 <__gmon_start__@plt>:
80482d0: ff 25 10 96 04 08 jmp *0x8049610
80482d6: 68 00 00 00 00 push $0x0
80482db: e9 e0 ff ff ff jmp 80482c0 <_init+0x30>
080482e0 <__libc_start_main@plt>:
80482e0: ff 25 14 96 04 08 jmp *0x8049614
80482e6: 68 08 00 00 00 push $0x8
80482eb: e9 d0 ff ff ff jmp 80482c0 <_init+0x30>
080482f0 <puts@plt>:
80482f0: ff 25 18 96 04 08 jmp *0x8049618
80482f6: 68 10 00 00 00 push $0x10
80482fb: e9 c0 ff ff ff jmp 80482c0 <_init+0x30>
Disassembly of section .text:
08048300 <_start>:
8048300: 31 ed xor %ebp,%ebp
8048302: 5e pop %esi
8048303: 89 e1 mov %esp,%ecx
8048305: 83 e4 f0 and $0xfffffff0,%esp
8048308: 50 push %eax
8048309: 54 push %esp
804830a: 52 push %edx
804830b: 68 d0 83 04 08 push $0x80483d0
8048310: 68 e0 83 04 08 push $0x80483e0
8048315: 51 push %ecx
8048316: 56 push %esi
8048317: 68 b4 83 04 08 push $0x80483b4
804831c: e8 bf ff ff ff call 80482e0 <__libc_start_main@plt>
8048321: f4 hlt
8048322: 90 nop
8048323: 90 nop
8048324: 90 nop
8048325: 90 nop
8048326: 90 nop
8048327: 90 nop
8048328: 90 nop
8048329: 90 nop
804832a: 90 nop
804832b: 90 nop
804832c: 90 nop
804832d: 90 nop
804832e: 90 nop
804832f: 90 nop
08048330 <__do_global_dtors_aux>:
8048330: 55 push %ebp
8048331: 89 e5 mov %esp,%ebp
8048333: 53 push %ebx
8048334: 8d 64 24 fc lea -0x4(%esp),%esp
8048338: 80 3d 20 96 04 08 00 cmpb $0x0,0x8049620
804833f: 75 3e jne 804837f <__do_global_dtors_aux+0x4f>
8048341: bb 30 95 04 08 mov $0x8049530,%ebx
8048346: a1 24 96 04 08 mov 0x8049624,%eax
804834b: 81 eb 2c 95 04 08 sub $0x804952c,%ebx
8048351: c1 fb 02 sar $0x2,%ebx
8048354: 83 eb 01 sub $0x1,%ebx
8048357: 39 d8 cmp %ebx,%eax
8048359: 73 1d jae 8048378 <__do_global_dtors_aux+0x48>
804835b: 90 nop
804835c: 8d 74 26 00 lea 0x0(%esi,%eiz,1),%esi
8048360: 83 c0 01 add $0x1,%eax
8048363: a3 24 96 04 08 mov %eax,0x8049624
8048368: ff 14 85 2c 95 04 08 call *0x804952c(,%eax,4)
804836f: a1 24 96 04 08 mov 0x8049624,%eax
8048374: 39 d8 cmp %ebx,%eax
8048376: 72 e8 jb 8048360 <__do_global_dtors_aux+0x30>
8048378: c6 05 20 96 04 08 01 movb $0x1,0x8049620
804837f: 8d 64 24 04 lea 0x4(%esp),%esp
8048383: 5b pop %ebx
8048384: 5d pop %ebp
8048385: c3 ret
8048386: 8d 76 00 lea 0x0(%esi),%esi
8048389: 8d bc 27 00 00 00 00 lea 0x0(%edi,%eiz,1),%edi
08048390 <frame_dummy>:
8048390: 55 push %ebp
8048391: 89 e5 mov %esp,%ebp
8048393: 8d 64 24 e8 lea -0x18(%esp),%esp
8048397: a1 34 95 04 08 mov 0x8049534,%eax
804839c: 85 c0 test %eax,%eax
804839e: 74 12 je 80483b2 <frame_dummy+0x22>
80483a0: b8 00 00 00 00 mov $0x0,%eax
80483a5: 85 c0 test %eax,%eax
80483a7: 74 09 je 80483b2 <frame_dummy+0x22>
80483a9: c7 04 24 34 95 04 08 movl $0x8049534,(%esp)
80483b0: ff d0 call *%eax
80483b2: c9 leave
80483b3: c3 ret
080483b4 <main>:
80483b4: 55 push %ebp
80483b5: 89 e5 mov %esp,%ebp
80483b7: 83 e4 f0 and $0xfffffff0,%esp
80483ba: 83 ec 10 sub $0x10,%esp
80483bd: c7 04 24 94 84 04 08 movl $0x8048494,(%esp)
80483c4: e8 27 ff ff ff call 80482f0 <puts@plt>
80483c9: c9 leave
80483ca: c3 ret
80483cb: 90 nop
80483cc: 90 nop
80483cd: 90 nop
80483ce: 90 nop
80483cf: 90 nop
080483d0 <__libc_csu_fini>:
80483d0: 55 push %ebp
80483d1: 89 e5 mov %esp,%ebp
80483d3: 5d pop %ebp
80483d4: c3 ret
80483d5: 8d 74 26 00 lea 0x0(%esi,%eiz,1),%esi
80483d9: 8d bc 27 00 00 00 00 lea 0x0(%edi,%eiz,1),%edi
080483e0 <__libc_csu_init>:
80483e0: 55 push %ebp
80483e1: 89 e5 mov %esp,%ebp
80483e3: 57 push %edi
80483e4: 56 push %esi
80483e5: 53 push %ebx
80483e6: e8 4f 00 00 00 call 804843a <__i686.get_pc_thunk.bx>
80483eb: 81 c3 19 12 00 00 add $0x1219,%ebx
80483f1: 83 ec 1c sub $0x1c,%esp
80483f4: e8 97 fe ff ff call 8048290 <_init>
80483f9: 8d bb 20 ff ff ff lea -0xe0(%ebx),%edi
80483ff: 8d 83 20 ff ff ff lea -0xe0(%ebx),%eax
8048405: 29 c7 sub %eax,%edi
8048407: c1 ff 02 sar $0x2,%edi
804840a: 85 ff test %edi,%edi
804840c: 74 24 je 8048432 <__libc_csu_init+0x52>
804840e: 31 f6 xor %esi,%esi
8048410: 8b 45 10 mov 0x10(%ebp),%eax
8048413: 89 44 24 08 mov %eax,0x8(%esp)
8048417: 8b 45 0c mov 0xc(%ebp),%eax
804841a: 89 44 24 04 mov %eax,0x4(%esp)
804841e: 8b 45 08 mov 0x8(%ebp),%eax
8048421: 89 04 24 mov %eax,(%esp)
8048424: ff 94 b3 20 ff ff ff call *-0xe0(%ebx,%esi,4)
804842b: 83 c6 01 add $0x1,%esi
804842e: 39 fe cmp %edi,%esi
8048430: 72 de jb 8048410 <__libc_csu_init+0x30>
8048432: 83 c4 1c add $0x1c,%esp
8048435: 5b pop %ebx
8048436: 5e pop %esi
8048437: 5f pop %edi
8048438: 5d pop %ebp
8048439: c3 ret
0804843a <__i686.get_pc_thunk.bx>:
804843a: 8b 1c 24 mov (%esp),%ebx
804843d: c3 ret
804843e: 90 nop
804843f: 90 nop
08048440 <__do_global_ctors_aux>:
8048440: 55 push %ebp
8048441: 89 e5 mov %esp,%ebp
8048443: 53 push %ebx
8048444: 8d 64 24 fc lea -0x4(%esp),%esp
8048448: a1 24 95 04 08 mov 0x8049524,%eax
804844d: 83 f8 ff cmp $0xffffffff,%eax
8048450: 74 12 je 8048464 <__do_global_ctors_aux+0x24>
8048452: bb 24 95 04 08 mov $0x8049524,%ebx
8048457: 90 nop
8048458: 8d 5b fc lea -0x4(%ebx),%ebx
804845b: ff d0 call *%eax
804845d: 8b 03 mov (%ebx),%eax
804845f: 83 f8 ff cmp $0xffffffff,%eax
8048462: 75 f4 jne 8048458 <__do_global_ctors_aux+0x18>
8048464: 8d 64 24 04 lea 0x4(%esp),%esp
8048468: 5b pop %ebx
8048469: 5d pop %ebp
804846a: c3 ret
804846b: 90 nop
Disassembly of section .fini:
0804846c <_fini>:
804846c: 55 push %ebp
804846d: 89 e5 mov %esp,%ebp
804846f: 53 push %ebx
8048470: 83 ec 04 sub $0x4,%esp
8048473: e8 00 00 00 00 call 8048478 <_fini+0xc>
8048478: 5b pop %ebx
8048479: 81 c3 8c 11 00 00 add $0x118c,%ebx
804847f: e8 ac fe ff ff call 8048330 <__do_global_dtors_aux>
8048484: 59 pop %ecx
8048485: 5b pop %ebx
8048486: c9 leave
8048487: c3 ret
------------------------------------------
On Sat, Dec 25, 2010 at 2:11 PM, Philip Herron <redbrain@xxxxxxxxxxx> wrote:
> On 25 December 2010 09:59, ali hagigat <hagigatali@xxxxxxxxx> wrote:
>> When we use some functions like printf in Linux C programs, libc.a is
>> linked with our program. Is it linked dynamically or statically?
>> Regards
>>
>
> You could probably google that but its static i am fairly sure you
> could always do gcc -v to see whats going on and try -nostdinc i think
> the option is to not do the standard includes.
>
> Hope this help! Now back to Christmas ;)
>
> --Phil
>
