Adding the assembly by GCC for the same program, for comparison.
On Thu, Aug 1, 2024 at 11:45, Jonathan M. Wilbur <jonathan@wilbur.space> wrote:
> Hello,
>
> When TinyCC compiles a program using nolibc's
> [crt.h](https://github.com/torvalds/linux/blob/21b136cc63d2a9ddd60d4699552b69c214b32964/tools/include/nolibc/crt.h),
> the resulting program always has an argc of 0, but this does not happen with
> GCC. I simply don't have a grasp on assembly enough to see what is wrong, but
> I have attached it if somebody could help me interpret it.
>
> Cheers,
>
> - Jonathan M. Wilbur
0000000000401540 <_start_c>:
401540: f3 0f 1e fa endbr64
401544: 41 55 push %r13
401546: 41 54 push %r12
401548: 4c 8d 67 08 lea 0x8(%rdi),%r12
40154c: 55 push %rbp
40154d: 53 push %rbx
40154e: 50 push %rax
40154f: 48 8b 1f mov (%rdi),%rbx
401552: 4c 8d 6c df 10 lea 0x10(%rdi,%rbx,8),%r13
401557: 4c 89 2d d2 4d 00 00 mov %r13,0x4dd2(%rip) #
406330 <environ>
40155e: 4c 89 e8 mov %r13,%rax
401561: 48 83 c0 08 add $0x8,%rax
401565: 48 83 78 f8 00 cmpq $0x0,-0x8(%rax)
40156a: 75 f5 jne 401561 <_start_c+0x21>
40156c: 48 89 05 b5 4d 00 00 mov %rax,0x4db5(%rip) #
406328 <_auxv>
401573: 48 c7 c5 e0 5f 40 00 mov $0x405fe0,%rbp
40157a: 48 81 fd e0 5f 40 00 cmp $0x405fe0,%rbp
401581: 73 09 jae 40158c <_start_c+0x4c>
401583: ff 55 00 callq *0x0(%rbp)
401586: 48 83 c5 08 add $0x8,%rbp
40158a: eb ee jmp 40157a <_start_c+0x3a>
40158c: 48 c7 c5 e0 5f 40 00 mov $0x405fe0,%rbp
401593: 48 81 fd e0 5f 40 00 cmp $0x405fe0,%rbp
40159a: 73 09 jae 4015a5 <_start_c+0x65>
40159c: ff 55 00 callq *0x0(%rbp)
40159f: 48 83 c5 08 add $0x8,%rbp
4015a3: eb ee jmp 401593 <_start_c+0x53>
4015a5: 89 df mov %ebx,%edi
4015a7: 4c 89 ea mov %r13,%rdx
4015aa: 4c 89 e6 mov %r12,%rsi
4015ad: e8 4e fa ff ff callq 401000 <main>
4015b2: 48 c7 c3 e0 5f 40 00 mov $0x405fe0,%rbx
4015b9: 89 c5 mov %eax,%ebp
4015bb: 48 39 1d 1e 4a 00 00 cmp %rbx,0x4a1e(%rip) #
405fe0 <__fini_array_end>
4015c2: 73 08 jae 4015cc <_start_c+0x8c>
4015c4: 48 83 eb 08 sub $0x8,%rbx
4015c8: ff 13 callq *(%rbx)
4015ca: eb ef jmp 4015bb <_start_c+0x7b>
4015cc: 89 ef mov %ebp,%edi
4015ce: e8 51 1f 00 00 callq 403524 <sys_exit>
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