Re: [bug #61226] A regression prevents generation of missing included dependency files.

[Alejandro Colomar (man-pages)]

On 10/26/21 3:20 PM, Alejandro Colomar (man-pages) wrote:
> Hi Paul and Dmitry,
>
> On 10/26/21 1:16 AM, Paul Smith wrote:
> > On Mon, 2021-10-25 at 17:51 -0400, Dmitry Goncharov via Bug reports and
> > discussion for GNU make wrote:
> > > On Monday, October 25, 2021, Alejandro Colomar (man-pages) <
> > > alx.manpages@gmail.com> wrote:
> > > > Why do I do this?  Because, if you remove a file from your tree, an
> > > > old .d file will require that file and make your build fail,
> > > > requiring you to clean before making again.
> > >
> > > This has been solved long ago. Check the awesome advanced dependency
> > > generation article by Paul.
> >
> > FYI:
> >
> >    
> > http://make.mad-scientist.net/papers/advanced-auto-dependency-generation/
> >
> > The issue you raise (as well as others) is discussed, hopefully
> > clearly, in this article [*].
> >
> >
> > [*] 
> > http://make.mad-scientist.net/papers/advanced-auto-dependency-generation/#depdelete 
>
> Thanks for sharing that great article!
>
> I'll definitely have to have a look at many or all of the articles in 
> that website!
>
> I've already applied some of the improvements there, reducing no-op make 
> times to 0.7 s in single-process and 0.35 with 'make -j'.  I'll keep 
> adding the other improvements too.

In the end, I couldn't use all of the features that the article shows.

Since I do a lot of static analysis to the files, I also have 
*.checkpatch.touch (and similar) targets created in the dependencies 
files, and since those tools can't generate dependencies files as side 
effects, I need an explicit rule for creating them.  Otherwise, if I 
create all of them at the compilation stage, it is very likely that at 
some point I only run static analysis and not compilation, and I'll have 
outdated dependencies files the next time I run static analysis, and I 
won't notice.

Maybe I could overcome this with some complicated workaround, but I 
don't think it's worth it: 0.7 s is already a very acceptable time :-) 
And it would probably be a bit obscure and maybe slower for full builds.

So I'm forced to create dependencies files not as side effects, but as 
real targets:


DEPTARGETS = -MT $<.checkpatch.touch -MT $<.clang-tidy.touch \
             -MT $<.cppcheck.touch -MT $<.cpplint.touch
DEPHTARGETS = $(DEPTARGETS) -MT $<.gch
DEPCTARGETS = $(DEPTARGETS) -MT $(builddir_)/$*.i
$(UNITS_h_d):   $(builddir)/%.d: $(INCLUDEDIR)/% $(mk) | $$(@D)/.
        $(CC)  $(CFLAGS)   -I $(INCLUDEDIR) -M -MP $(DEPHTARGETS) -MF $@ $<
$(UNITS_hxx_d): $(builddir)/%.d: $(INCLUDEDIR)/% $(mk) | $$(@D)/.
        $(CXX) $(CXXFLAGS) -I $(INCLUDEDIR) -M -MP $(DEPHTARGETS) -MF $@ $<

$(UNITS_c_d):   $(builddir_)/%.d: $(SRCDIR)/% $(mk) | $$(@D)/.
        $(CC)  $(CFLAGS)   -I $(INCLUDEDIR) -M -MP $(DEPCTARGETS) -MF $@ $<
$(UNITS_cxx_d): $(builddir_)/%.d: $(SRCDIR)/% $(mk) | $$(@D)/.
        $(CXX) $(CXXFLAGS) -I $(INCLUDEDIR) -M -MP $(DEPCTARGETS) -MF $@ $<

<https://github.com/alejandro-colomar/libalx>



Thanks!

Alex

> Cheers,
>
> Alex


--
Alejandro Colomar
Linux man-pages comaintainer; https://www.kernel.org/doc/man-pages/
http://www.alejandro-colomar.es/