Date: Mon, 30 Oct 1995 13:25:08 -0500
From: kagel AT quasar DOT bloomberg DOT com
To: sorinb AT sky DOT dsp DOT pub DOT ro
Cc: djgpp AT sun DOT soe DOT clarkson DOT edu
Subject: Re: Weird stuff in COFF files
Reply-To: kagel AT ts1 DOT bloomberg DOT com

   Date: Fri, 27 Oct 1995 14:46:20 --200
   From: sorinb AT sky DOT dsp DOT pub DOT ro (Balea Mihai Sorin)


     I was playing around with djgpp 1.12m4 ( gcc 2.6.3 ) when I noticed
     something
   quite strange. The resulting COFF file was different, although I compiled
   the same source file ( about 30 lines long ) under *the same* conditions (
   meaning the same command line and the same environment ).Further browsing of

The COFF header contains compile time so cmp or comp will report a difference
anytime the source is recompiled. 

   the output revealed even stranger things. The end of COFF file was filled
   with a lot of apparently unnecessary stuff like functions identifiers and
   assembly labels.  Even worse : in some cases I found a partial copy of my
   directory tree and/or pieces of C source. Worth mentioning : my program
   behaves identically each time I build it. And also, I did not include any
   debug info !


Some of this is symbol table space and basic debug records, the rest is slack
space at the end of the file filled with garbage either from disk or from
memory.  DJGPP does not null fill the file out to the next sector boundary.  In
any case this is not loaded into memory when the .exe is read so, of course,
this garbase has no effect on your run-time behavior.


     Is there anyone who can tell me why this happens and how it can be stopped
   ( if possible ) ?

     Is there any on line description of COFF file format ? I wonder if an
     executable file compressor ( something like PKLITE or LZEXE ) would be
     possible
   ( I'm not sure if protected mode allows it ).

     Thanks in advance !
-- 
Art S. Kagel, kagel AT ts1 DOT bloomberg DOT com

Variety is the soul of pleasure.  --  Aphra Behn