Hi Philip,
it looks like a good idea. Do you think it worths to be discussed with
automake hackers?
Cheers,
Giuseppe
Philip Guenther <guent...@gmail.com> writes:
> On Fri, Apr 11, 2008 at 2:45 PM, Giuseppe Scrivano<gscriv...@gnu.org> wrote:
>> I could find on this ML archives only a thread about this subject: to
>> consider the file checksum instead of the timestamp.
>> Other systems like scons already support this feature and it would be
>> great to have it for GNU Make too.
>
> This is a long dead thread (it's been sitting in my mailbox for a
> year, ouch), but I'll throw in my two cents that a makefile can
> implement this for itself with pattern rules. Consider:
>
> ----
> %.o: %.c
> %.o.new: %.c
> $(COMPILE.c) -o $@ $<
> %.o: %.o.new
> @{ [ -f $...@.md5 ] && md5sum -c --status $...@.md5; } || \
> { md5sum $< >$...@.md5; cp $< $@; }
>
> .SECONDARY:
> -----
>
> Poof, if you touch a .c file without making changes that affect the
> compiler output, the executable will not be relinked. Indeed, the
> presence of the .SECONDARY target means the only thing that will be
> rerun each time is the md5sum.
>
> Yes, this is non-trivial to use, but it's also completely flexible,
> letting you use whatever checksum comparison you want (need to strip
> comments or RCS/CVS tags from the file before checksumming it? Sure!)
> and can be used Right Now.
>
> Anyway, we now return you to your originally scheduled mailing list.
>
>
> Philip Guenther
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