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Message-ID:	<001201c2a820$26daf9a0$6fc82486@medschool.dundee.ac.uk>
Reply-To:	<fergus AT bonhard DOT uklinux DOT net>
From:	<fergus AT bonhard DOT uklinux DOT net>
To:	<cygwin AT cygwin DOT com>
Cc:	<fergus AT bonhard DOT uklinux DOT net>
Subject:	Repeated gcc yields differing .exe files
Date:	Fri, 20 Dec 2002 12:05:56 -0000
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I found this just now. I'm afraid I don't know enough about gcc to deduce
whether this is just yet another symptom of problems already reported or
something else, that genuinely matters (I think it does) and that can be
mended (I hope it can).

I just repeatedly used gcc with hello.c attached to get this:

~/tmp> gcc -o hello hello.c; md5sum hello.exe
15fbfaadc53cede5d797eb544dae032e *hello.exe
~/tmp> gcc -o hello hello.c; md5sum hello.exe
3a7d9a1536e0b3dcb4fa8557a2933ffb *hello.exe
~/tmp> gcc -o hello hello.c; md5sum hello.exe
952a3bee8d35b627a92c679640e1d1df *hello.exe

The fact that hello.exe alters seems a bit non-optimal to me, given that
md5sums are a pretty standard way for people like you and me to check that
we're running the same stuff, intended to do the same thing. Incidentally,
it's always the same two bytes that alter:

~/tmp> cmp -l hello.exe hello1.exe
  137  74 254
  217  33 213
~/tmp> cmp -l hello.exe hello2.exe
  137  74 257
  217  33 216
~/tmp> cmp -l hello.exe hello3.exe
  137  74 262
  217  33 221

I had an earlier problem with a _long_ myfile.c giving variant myfile.exe. I
knew you wouldn't like to be bothered with myfile.c which is why I looked at
hello.c. The variations in successive copies of myfile.exe were again in
bytes 137 and 217.

Fergus

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Content-Type: application/octet-stream;
	name="hello.c"
Content-Transfer-Encoding: quoted-printable
Content-Disposition: attachment;
	filename="hello.c"

=0A=
#include <stdio.h>=0A=
main()=0A=
{=0A=
  (void) printf("Hello World\n");=0A=
  return (0);=0A=
}=0A=


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