🚀 go-pugleaf

ara@zurich.ai.mit.edu (Allan Adler) writes:
>First, it seems to me that every compiler and every assembler must have its
>own idiosyncratic way of producing the executable. Is that true?

ross@zooid.guild.org (Ross Ridge) writes:
>For compilers yes, for assemblers no.  With assemblers every byte of
>the execuatable is under the programmers control.

mlevis@ringer.cs.utsa.edu (Mike Levis) writes:
>Actually, assemblers have their own way of producing executables, too.
>There is a share-ware assembler (I think it is called A86) that even
>says that it creates opcodes different from other assemblers.  This
>way, the author can sue unregistered owners for not registering.
>There are different ways an assembler can create a "fingerprint".
>One example is ``MOV BX, AX''.  An assembler can generate either
>``89h C3h'' or ``8Bh D8h'' for the opcode (I don't have A86, so I
>don't know which opcode set it uses for ``MOV BX, AX'').

True, this can be used to identify assemblers.  I hadn't thought
of that.  But it isn't of any use in helping you understand
the programme.

>Likewise, an assembler can optimize the code for speed and/or size.
>For example, I have TASM, which converts a far call into the same
>segment into a push cs and near call.
>
>TASM also automatically generates code for you, such as when using
>Language modifiers.  For example, you can call a C function from
>your ASM program.  TASM will push your parameters (using the C
>parameter passing protocol), make the call, then adjust the stack
>for you.

Neither of these examples help you identify the assembler, the code
generated by TASM could've easily been generated explicitly by another 
assembler or even automatically by a compiler.  They're still also fully
under control of the programmer.  The second example however, a programme
using the C language calling convention, whether automatically or not is
something that can be used to gain some insight into the programme.

						Ross Ridge

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