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Article View: comp.os.msdos.programmer
Article #1477

Re: studying executables

#1477
From: Duncan Murdoch
Date: Sun, 13 Sep 1992 02:42
53 lines
2989 bytes
In article <2186.2AB2264A@catpe.alt.za> Louis.Mandelstam@p2.f42.n7101.z5.fidonet.org (Louis Mandelstam) 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.
>
>Any court that accepts THAT as evidence needs a 1 exavolt discharge 
>in the right place..
>
>What if the programmer created the executable in DEBUG, hand-changed some 
>of the bytes in the executable after linking or <gulp> did it in machine 
>language?

The actual claim (quoted from the A86 docs) is this:

6. A86 takes advantage of situations in which more than one set
   of opcodes can be generated for the same instruction.  (For
   example, MOV AX,BX can be generated using either an 89 or 8B
   opcode, by reversing fields in the following ModRM byte.  Both
   forms are absolutely identical in functionality and execution
   speed.)  A86 adopts an unusual mix of choices in such
   situations.  This creates a code-generation "footprint" that
   occupies no space in your program file, but will enable me to
   tell, and to demonstrate in a court of law, if a non-trivial
   object file has been produced by A86. The specification for
   this "footprint" is sufficiently obscure and complicated that
   it would be impossible to duplicate by accident.  I claim
   exclusive rights to the particular "footprint" I have chosen,
   and prohibit anyone from duplicating it.  This has at least
   two specific implications:

   a. Any assembler that duplicates the "footprint" is mine.  If
      it is not identified as mine and issued under these terms,
      then those who sell or distribute the assembler will be
      subject to prosecution.

   b. Any program marked with the "footprint" has been produced
      by my assembler.  It is subject to condition 5 above.


I don't know if he's ever tried to enforce this. It's pretty much moot these 
days, as other assemblers have come down in price a lot since A86 came out, 
and surpassed its capabilities in a lot of areas.  I still use A86 a bit, 
because I like its language definition better than MASM's or TASM's, 
but more often just use the inline assembler in Turbo Pascal (which is 
a MASM subset, but a lot more convenient than a separate assembler).

Duncan Murdoch
dmurdoch@mast.queensu.ca
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From: dmurdoch@mast.queensu.ca (Duncan Murdoch)
Subject: Re: studying executables
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Date: Sun, 13 Sep 1992 02:42:33 GMT