Re: [PATCH v2 3/5] doc: remove unnecessary rm instances

[Felipe Contreras <felipe.contreras@gmail.com>]

Jeff King wrote:
> On Fri, May 14, 2021 at 06:56:29AM -0500, Felipe Contreras wrote:
> 
> > Commits 50cff52f1a (When generating manpages, delete outdated targets
> > first., 2007-08-02) and f9286765b2 (Documentation/Makefile: remove
> > cmd-list.made before redirecting to it., 2007-08-06) created these rm
> > instances for a very rare corner-case: building as root by mistake.
> > 
> > It's odd to have workarounds here, but nowhere else in the Makefile--
> > which already fails in this stuation, starting from
> > Documentation/technical/.
> 
> Aren't there tons more that you end up removing in the next patch? E.g.:
> 
>    doc.dep : $(docdep_prereqs) $(DOC_DEP_TXT) build-docdep.perl
>   -       $(QUIET_GEN)$(RM) $@+ $@ && \
>   -       $(PERL_PATH) ./build-docdep.perl >$@+ $(QUIET_STDERR) && \
>   -       mv $@+ $@
>   +       $(QUIET_GEN)$(PERL_PATH) ./build-docdep.perl >$@ $(QUIET_STDERR)
> 
> That does differ in that it removes $@+, too, but the premise is the
> same (we know that $@+ could not be a problem, as we're about to
> clobber it anyway).
> 
> I'm OK with getting rid of all of them, but it seems like it ought to be
> happening all in this patch.

Yeah, but the rationale is different.

  1. $(RM) $@: these remove the target file because of permissions
     (i.e. root owned)
  2. $(RM) $@+ $@ && $(CODE) && mv $@+ $@: these are for interrupted builds

To get rid of #2 we need an alternative solution, like .DELETE_ON_ERROR,
to get rid of #1 we don't, we can just do it.

-- 
Felipe Contreras