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From: Ismail Donmez <ismail AT i10z DOT com>
Date: Wed, 4 May 2016 20:21:00 +0300
Message-ID: <CAFo71_4uBbNZ6JakbNE3mJ3HgvFRnFa-dK+GSrNdpmds1iXzow@mail.gmail.com>
Subject: Re: Deterministic builds
To: cygwin AT cygwin DOT com
Content-Type: text/plain; charset=UTF-8
X-IsSubscribed: yes

Hi,

On Wed, May 4, 2016 at 4:38 PM, Ken Brown <kbrown AT cornell DOT edu> wrote:
> Is it possible to build an executable on Cygwin so that subsequent builds
> (with no change in source) produce identical results?  Currently, the
> timestamp embedded in executables prevents this.  (I don't know if that's
> the only obstacle.)
>
> For example:
>
> $ cat hello.c
> #include <stdio.h>
> int
> main ()
> {
>  printf("Hello, world!\n");
>  return 0;
> }
>
> $ gcc hello.c -o hello1
>
> $ gcc hello.c -o hello2
>
> $ objdump -p hello1.exe | grep Time/Date
> Time/Date               Wed May  4 09:20:24 2016
>
> $ objdump -p hello2.exe | grep Time/Date
> Time/Date               Wed May  4 09:20:29 2016

You can easily disable this feature:

latte ~ > gcc -Wl,--no-insert-timestamp hello.c
latte ~ > objdump -p a.exe | grep Time/Date
Time/Date               Thu Jan  1 03:31:53 1970
latte ~ > gcc -Wl,--no-insert-timestamp hello.c
latte ~ > objdump -p a.exe | grep Time/Date
Time/Date               Thu Jan  1 03:31:53 1970

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