Re: [Tinycc-devel] [BUG] The main function parameter is missing.

[grischka]

On 07.06.2024 15:03, Edward Gynt wrote:
> I am having trouble reproducing your issue. My .exe files output the correct information. 
> The "C file" code you mention doesn't mark main as a __thiscall, but your 
> decompiled function lists sub_401000 as __thiscall. Why?
> I don't own IDA so I can't reproduce with IDA.

Hi Ed,

honestly there are several issues with your patch.
- thiscall_nb_regs uninitialized :
     causes compiled code crash mostly
- load(get_reg(RC_ECX), vtop) :
     ECX may get overwritten when other params are loaded
- too much code and funny variables (int func_call2) anyway seen that
  FUNC_THISCALL is identical to FUNC_FASTCALLW except fastcall_nb_regs = 1;
  instead of = 2;

So you'd really better go along the route that's already proven to
work instead of trying to be smart ;)

-- gr

> What I do notice is that using i386-win32-tcc.exe (compiled with gcc or tcc) I 
> get identical output to before my commit.
> With tcc.exe (compiled with gcc or tcc, which in turns was built with 
> build-tcc.bat -x), I get the situation that ecx is stored in the stack and then 
> moved into eax. Very strange.
> So the x86_64 build is affected. Before I start digging into the code 
> (misplaced #ifdef somewhere?) I want to verify the byte code with you to make 
> sure we are talking about the same issue.
> Can you post yours (objdump -D) ?
>
> Compiled with version on branch mob after my commit:
>
> 00401000 <.text>:
>    401000:       55                      push   %ebp
>    401001:       89 e5                   mov    %esp,%ebp
>    401003:       81 ec 04 00 00 00       sub    $0x4,%esp
>    401009:       90                      nop
>    40100a:       89 4d fc                mov    %ecx,-0x4(%ebp)
>    40100d:       8b 45 fc                mov    -0x4(%ebp),%eax
>    401010:       50                      push   %eax
>    401011:       b8 00 20 40 00          mov    $0x402000,%eax
>    401016:       50                      push   %eax
>    401017:       e8 54 02 00 00          call   0x401270
>    40101c:       83 c4 08                add    $0x8,%esp
>    40101f:       b8 0b 20 40 00          mov    $0x40200b,%eax
>    401024:       50                      push   %eax
>    401025:       e8 4e 02 00 00          call   0x401278
>    40102a:       83 c4 04                add    $0x4,%esp
>    40102d:       b8 00 00 00 00          mov    $0x0,%eax
>    401032:       c9                      leave
>    401033:       c3                      ret
>
> Compiled with version on branch mob before my commit:
>
> 00401000 <.text>:
>    401000:       55                      push   %ebp
>    401001:       89 e5                   mov    %esp,%ebp
>    401003:       81 ec 00 00 00 00       sub    $0x0,%esp
>    401009:       90                      nop
>    40100a:       8b 45 08                mov    0x8(%ebp),%eax
>    40100d:       50                      push   %eax
>    40100e:       b8 00 20 40 00          mov    $0x402000,%eax
>    401013:       50                      push   %eax
>    401014:       e8 57 02 00 00          call   0x401270
>    401019:       83 c4 08                add    $0x8,%esp
>    40101c:       b8 0b 20 40 00          mov    $0x40200b,%eax
>    401021:       50                      push   %eax
>    401022:       e8 51 02 00 00          call   0x401278
>    401027:       83 c4 04                add    $0x4,%esp
>    40102a:       b8 00 00 00 00          mov    $0x0,%eax
>    40102f:       c9                      leave
>    401030:       c3                      ret
>
>
>
> On Thu, Jun 6, 2024 at 5:30 PM HarukaMomono via Tinycc-devel <tinycc-devel@nongnu.org 
> <mailto:tinycc-devel@nongnu.org>> wrote:
>
>     commit:3b943bec5de423e234b5f92d9a8f110ad66a85a1
>     author:Gynt <Gynt@users.noreply.github.com 
> <mailto:Gynt@users.noreply.github.com>>
>                 Mon, 3 Jun 2024 19:52:34 +0800 (3 13:52 +0200)
>     committer:Gynt <Gynt@users.noreply.github.com 
> <mailto:Gynt@users.noreply.github.com>>
>                      Mon, 3 Jun 2024 19:56:32 +0800 (3 13:56 +0200)
>     tree:3c7fd4f944e9417b6bf2c95c21c9e8c9ee671b11
>     parent:8cd21e91ccee3baf15ad2f8cba9cbc4b618695a0
>
>     envs: windows 10; gcc version 14.1.0 (MinGW-W64 x86_64-ucrt-posix-seh, 
> built by Brecht Sanders, r1)
>
>     In this branch, I built it using gcc, the build command: build-tcc.bat -x
>
>     C file:
>     #include <stdio.h>
>     #include <stdlib.h>
>
>     int main(int argc, const char **argv, const char **envp) {
>     printf("argc = %d\n", argc);
>     system("pause");
>     return 0;
>     }
>
>     Compile Commands:
>     tcc.exe -std=c11 -m32 -o test.exe test.c
>
>     result:
>     argc = 9908136
>
>     Decompile using IDA:
>     int __thiscall sub_401000(void *this)
>     {
>        printf("arg num = %d\n", this);
>        system("pause");
>        return 0;
>     }
>
>     There are missing parameters.
>
>     
> ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
>
>     百野悠
>     antisnow@qq.com
>
>     
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