LCC-- How to stop debugger from breaking at the start of the application?

Question

I'm not sure of how many users there are out there that use the LCC C compiler and the WEdit GUI for Windows but it has a "feature" that is can get to be quite annoying. When you start an application with the debugger, it breaks the application at the start of the Main function. How can I cut this off so that the debugger immediately executes the code until I halt it or it hits a break point that I've created?

Answer 1

Wow, people still use LCC... Last time I used it was ~10 years ago.

I decompiled wedit.exe and can confirm there is no official way to disable this behavior.

I patched the binary if that works for you. I uploaded it here.

To those who concerned about viruses and such I patched wedit taken from here. About box says it's version 4.0 compiled at Sep 16 2009.

Here is patched function to those who interested:

int __cdecl sub_44CF0D(HANDLE hProcess)
{
  int result; // eax@1
  int v2; // ST0C_4@10
  int v3; // eax@20
  int v4; // eax@23
  int v5; // eax@25
  int v6; // [sp+10h] [bp-68h]@11
  int v7; // [sp+14h] [bp-64h]@1
  struct _DEBUG_EVENT DebugEvent; // [sp+18h] [bp-60h]@1

  v7 = 1;
  result = WaitForDebugEvent(&DebugEvent, dwMilliseconds);
  if ( result )
  {
    sub_44C67A(&DebugEvent);
    if ( DebugEvent.dwDebugEventCode == 1 )
    {
      if ( DebugEvent.u.Exception.ExceptionRecord.ExceptionCode == EXCEPTION_ACCESS_VIOLATION
        && !(dword_482860 & 1)
        && !dword_484328
        && DebugEvent.u.Exception.dwFirstChance )
      {
        sub_44E1A5(0);
        sub_44CEB2(v2);
        return ContinueDebugEvent(DebugEvent.dwProcessId, DebugEvent.dwThreadId, 0x80010001u);
      }
      v6 = 0;
      v7 = sub_44D2C4((int)&DebugEvent, hProcess, (int)&v6);
      if ( v6 && DebugEvent.u.Exception.dwFirstChance )
        return ContinueDebugEvent(DebugEvent.dwProcessId, DebugEvent.dwThreadId, 0x80010001u);
      goto LABEL_41;
    }
    if ( DebugEvent.dwDebugEventCode == 3 )
    {
      if ( dword_483C94 )
      {
        dword_48428C = 1;
LABEL_41:
        if ( dword_483C6C )
          sub_44ECDC();
        if ( v7 )
        {
          result = ContinueDebugEvent(DebugEvent.dwProcessId, DebugEvent.dwThreadId, 0x10002u);
        }
        else
        {
          dword_49BF68 = 1;
          ResetEvent(dword_484AE4);
          dword_4843C8 = DebugEvent.dwThreadId;
          result = sub_4524CD();
        }
        return result;
      }
      Sleep(0x32u);
      dword_49BF64 = 1;
      dword_49BF68 = 1;
      qword_483C74 = __PAIR__(
                       (unsigned int)DebugEvent.u.Exception.ExceptionRecord.ExceptionAddress,
                       DebugEvent.u.Exception.ExceptionRecord.ExceptionInformation[2]);
      if ( dword_484288 )
        ::hProcess = (HANDLE)DebugEvent.u.Exception.ExceptionRecord.ExceptionFlags;
      else
        ::hProcess = hProcess;
      dword_483C84 = DebugEvent.dwProcessId;
      hThread = DebugEvent.u.Exception.ExceptionRecord.ExceptionRecord;
      dword_483C9C = (HANDLE)DebugEvent.u.Exception.ExceptionRecord.ExceptionCode;
      dwThreadId = DebugEvent.dwThreadId;
      dword_483C94 = 0;
      if ( sub_45A83A() )
      {
        v4 = sub_4026A6(28);
        dword_484330 = v4;
        *(_DWORD *)(v4 + 4) = hThread;
        *(_DWORD *)(v4 + 8) = dwThreadId;
        if ( dword_484288 )
        {
          sub_455B58();
        }
        else
        {
          Sleep(0x64u);
          v5 = sub_45AAFC();
          if ( !v5 )
            return PostMessageA(dword_4849EC, 0x111u, 0x64u, 0);
          if ( dword_484354 )
            goto LABEL_50;
          sub_455B58();
          if ( dword_483C70 && *(_DWORD *)(dword_483C70 + 52) )
            *(_DWORD *)(*(_DWORD *)(dword_483C70 + 52) + 36) = sub_451577(**(_DWORD **)(dword_483C70 + 52), 1u);
          v5 = *(_DWORD *)(dword_483C70 + 52);
          if ( v5 && *(_DWORD *)(v5 + 36) )
          {
LABEL_50:
            if ( !dword_483C6C )
              sub_44E92A(v5);
            sub_44CC3D();
            sub_451600();
            PostMessageA(dword_4849EC, 0x111u, 0x154u, 0);
          }
          else
          {
            sub_4029CA("Imposible to find %s\nRunning without source display", *(_DWORD *)(dword_483C70 + 20));
            dword_484344 = 1;
            v7 = 1;
            PostMessageA(dword_4849EC, 0x111u, 0x154u, 0);
          }
        }
        goto LABEL_41;
      }
      dword_484338 = 1;
      v3 = sub_44DB56(qword_483C74);
      if ( v3 )
        *(_BYTE *)(v3 + 29) &= 0xFDu;
      result = ContinueDebugEvent(DebugEvent.dwProcessId, DebugEvent.dwThreadId, 0x10002u);
    }
    else
    {
      if ( DebugEvent.dwDebugEventCode != 5 )
        goto LABEL_41;
      if ( DebugEvent.dwProcessId != dword_483C84 )
      {
        v7 = 1;
        goto LABEL_41;
      }
      dword_49BF64 = 0;
      dword_49BF68 = 1;
      dword_481614 = 0;
      result = sub_402A32(4520, SLOBYTE(DebugEvent.u.Exception.ExceptionRecord.ExceptionCode));
      if ( !dword_483C6C )
        result = sub_40B155(lpCmdLine);
    }
  }
  else
  {
    if ( dword_483C6C )
      result = sub_44ECDC();
  }
  return result;
}

if under LABEL_50 is what I patched (from 0x75 to 0xEB).

It was easy to spot the place because I expected WriteProcessMemory to be used to write 0xCC at entry-point of application that is being debugged.