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From: Ed Prochak on 7 Apr 2010 01:02
On Apr 6, 9:44 pm, Tim Wescott <t...(a)seemywebsite.now> wrote:
> a7yvm109gf...(a)netzero.com wrote:
> > On Apr 6, 7:50 pm, NoEmail...(a)execpc.com (Chris Giese) wrote:
> >> a7yvm109gf...(a)netzero.com wrote:
> >>> Hello
> >>> Back when I was doing assembler on the 8051, I used some compiler
> >>> specific labels to include the date and time of compilation in a
> >>> string. The microcontroller could then send out this information on
> >>> request.
> >>> How could I do this now?
> >> #include <stdio.h>
> >> int main(void) { printf("I was compiled on %s\n", __DATE__); return 0; }
>
> > I'm tickled pink by this, thanks.
> > Was I searching for the wrong term, "timestamp"? This info didn't
> > exactly pop out at me.
>
> Apparently!
>
> Note #1: __TIME__ and __DATE__ are part of the ANSI C standard; while
> I'm sure there are compilers that don't support them, I haven't run into
> one.
>
> Note #2: If you are interested in version control, one of the things
> that you want is for a 'production' build for a particular version of
> software to come out bit-exact each and every time.  You want this,
> because five years down the road when some Very Important Customer wants
> Just One Change, or if you have to track down some Dread Bug, it is
> exceedingly soothing to be able to verify that you can, indeed, check
> out and rebuild some hex file that's going into production hardware.
>
> This rules out using time and date stamping _on production builds_.  My
> preferred process is to have a "version" header or source file that gets
> changed to match the version, and which takes a "development code" flag
> that tells it to insert compile time and date instead.
>
> --
> Tim Wescott
> Control system and signal processing consultingwww.wescottdesign.com

Yes time stamping the source files is better, but it is possible to do
comparison scripts that check all but a small fixed set of bytes
(those bytes being the time/date compiled). Had to do exactly that
back in the late '80s.

So again: do it with source file dates (generated by your Source code
controls system).

Ed
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