[Top][All Lists]

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: Force a file to be compiled always

From: Dave Hart
Subject: Re: Force a file to be compiled always
Date: Thu, 4 Nov 2010 15:46:50 +0000

On Thu, Nov 4, 2010 at 13:46 UTC, Valentin David
<address@hidden> wrote:
> You probably want to have one object that has symbols for the date and
> the time, and this object to be depending on other objects.

The NTP reference implementation does something along these lines.
Every time any consituent libraries or objects change for a binary, an
updated version.c is generated containing the build timestamp as well
as a generation counter for repeated builds in the same directory.

version.c contains a line like:
char * Version = "ntpd address@hidden Nov 03 19:17:08.92
(UTC-00:00) 2010  (1)" ;

(1) is the generation counter.

This is wired into the by omitting version.c from
program_SOURCES, adding version.o to program_LDADD, and adding a rule
to build it like:

version.o: $(ntpq_OBJECTS) ../libntp/libntp.a Makefile $(top_srcdir)/version
        env CSET=`cat $(top_srcdir)/version` $(top_builddir)/scripts/mkver ntpq
        $(COMPILE) -c version.c

mkver is a shell script which uses the version number from, the repository revision from $CSET, and the current
date/time to produce version.c.

The dependency of version.o on Makefile, combined with the practice of
the NTP build shell script of invoking config.status (which
unconditionally regenerates Makefile) before make, means that a run of
the "build" script always generates updated version.c files with the
current timestamp, even if nothing else has changed.

I am not responsible for inventing this scheme, and I may have missed
an important part.

Dave Hart

reply via email to

[Prev in Thread] Current Thread [Next in Thread]