Re: Makefile logic to create Guix documentation

[Ludovic Courtès]

Hi,

Chris Marusich <cmmarusich@gmail.com> skribis:

> First, consider this snippet from doc/local.mk:
>
> # We cannot add new dependencies to `%D%/guix.pdf' & co. (info "(automake)
> # Extending").  Using the `-local' rules is imperfect, because they may be
> # triggered after the main rule.  Oh, well.
> pdf-local: $(DOT_FILES=%.dot=$(top_srcdir)/%.pdf)
> info-local: $(DOT_FILES=%.dot=$(top_srcdir)/%.png)
> ps-local: $(DOT_FILES=%.dot=$(top_srcdir)/%.eps)              \
>         $(top_srcdir)/%D%/images/coreutils-size-map.eps
> dvi-local: ps-local
>
>
> What is this syntax called?  I checked the Make, Automake, and Autoconf
> manuals, but I couldn't find anything.  I'm talking about this syntax:
>
>   info-local: $(DOT_FILES=%.dot=$(top_srcdir)/%.png)

These are GNU Make substitutions (info "(make) Substitution Refs").

> It looks like when you added this, you intended to add a *.png
> prerequisite to the info-local target for every equivalent *.dot file
> that exists.  My guess is you want to ensure that the PNG files are
> generated before the info page gets created, since the PNG files are
> required in order to build the info page.  However, is it possible you
> meant to write it like the following instead?  (The first "=" has been
> replaced with a ":".)
>
>   info-local: $(DOT_FILES:%.dot=$(top_srcdir)/%.png)
>                          
> When using ":", I recognize this syntax as a "substitution reference"
> (see: (make) Substitution Refs).  However, I do not know what it is
> supposed to be when the ":" is replaced with a "=".  Is it a typo?

Ah yes, definitely!  I didn’t even notice when reading it above.
You’re welcome to make that change if nothing bad happens!

> Second, I noticed some rules like the following:
>
> .dot.eps:
>       $(AM_V_DOT)$(DOT) -Teps $(DOT_OPTIONS) < "$<" > "$(srcdir)/$@.tmp"; \
>       mv "$(srcdir)/$@.tmp" "$(srcdir)/$@"

Julien already replied; this is POSIX make notation.

Thanks,
Ludo’.