I have a written piece of code in assembly and at some points of it, I want to jump to a label in C
. So I have the following code (shortened version but still, I am having the same problem):
#include <stdio.h>
#define JE asm volatile("jmp end");
int main(){
printf("hi\n");
JE
printf("Invisible\n");
end:
printf("Visible\n");
return 0;
}
This code compiles, but there is no end
label in the disassembled version of the code.
If I change the label name from end
to any other thing (let's say l1
, both in asm code(jmp l1
) and in the C
code), the compiler says that
main.c:(.text+0x6b): undefined reference to `l1'
collect2: error: ld returned 1 exit status
Makefile:2: recipe for target 'main' failed
make: *** [main] Error 1
I have tried different things(different length, different cases, upper, lower, etc.) and I think it only compiles with end
label. And with end
label, I am receiving segmentation fault because, there is no end
label in the disassembled version.
Compiled with: gcc -O0 main.c -o main
Disassembled code:
000000000000063a <main>:
63a: 55 push %rbp
63b: 48 89 e5 mov %rsp,%rbp
63e: 48 8d 3d af 00 00 00 lea 0xaf(%rip),%rdi # 6f4 <_IO_stdin_used+0x4>
645: e8 c6 fe ff ff callq 510 <puts@plt>
64a: e9 c9 09 20 00 jmpq 201018 <_end> # there is no _end label!
64f: 48 8d 3d a1 00 00 00 lea 0xa1(%rip),%rdi # 6f7 <_IO_stdin_used+0x7>
656: e8 b5 fe ff ff callq 510 <puts@plt>
65b: 48 8d 3d 9f 00 00 00 lea 0x9f(%rip),%rdi # 701 <_IO_stdin_used+0x11>
662: e8 a9 fe ff ff callq 510 <puts@plt>
667: b8 00 00 00 00 mov $0x0,%eax
66c: 5d pop %rbp
66d: c3 retq
66e: 66 90 xchg %ax,%ax
So, the questions are:
- Am I doing something wrong? I have seen this kind of jumps (from assembly to C) in codes. I can provide example links.
- Why the compiler/linker cannot find
l1
but can findend
?