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   comp.lang.asm.x86      Ahh, the lost art of x86 assembly      4,675 messages   

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   Message 4,246 of 4,675   
   Bernhard Schornak to All   
   Re: Refuting the {Linz, Sipser and Kozen   
   22 Dec 20 11:07:44   
   
   From: schornak@nospicedham.web.de   
      
   olcott wrote:   
      
   _H_Hat:   
   [000005e6](01)  55                  push ebp   
   [000005e7](02)  8bec                mov ebp,esp   
   [000005e9](01)  51                  push ecx   
   [000005ea](03)  8b4508              mov eax,[ebp+08]   
   [000005ed](01)  50                  push eax   
   [000005ee](03)  8b4d08              mov ecx,[ebp+08]   
   [000005f1](01)  51                  push ecx   
   [000005f2](05)  e8effdffff          call 000003e6   
   [000005f7](03)  83c408              add esp,+08   
   [000005fa](03)  8945fc              mov [ebp-04],eax   
   [000005fd](04)  837dfc00            cmp dword [ebp-04],+00   
   [00000601](02)  7404                jz 00000607   
   [00000603](02)  ebfe                jmp 00000603   
   [00000605](02)  eb01                jmp 00000608   
   [00000607](01)  f4                  hlt   
   [00000608](02)  8be5                mov esp,ebp   
   [0000060a](01)  5d                  pop ebp   
   [0000060b](01)  c3                  ret   
      
      
   0603 jumps to itself. Reduce to   
      
   _H-Hat:movl  0x0C(%esp), %eax   
           subl  $0x08,      %esp   
           movl  %eax,       0x00(%esp)   
           movl  %eax,       0x04(%esp)   
           call  _WHATEVER_THAT_IS   
           testl %eax,       %eax   
           je    0f   
       L00:jmp   L00                      # loop forever   
         0:hlt                            # CLI/STI?   
           addl $0x08,       %esp   
           ret   
      
      
      
   As long as the code at 0x03E6 is unknown, it is impossible to tell   
   anything. _H_Hat itself does nothing ... except wasting clocks and   
   electrical power when the returned value is not zero.   
      
   The only thing I can see in your debug trace is that you would run   
   out of stack, if the debugger did not stop your attempts with this   
   error message before ESP reached your stack's bottom. Maybe a good   
   proof the debugger works well, but nothing else... ;)   
      
      
   Merry Winter Solstice!   
      
   Bernhard Schornak   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)   

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