Re: Flag --no-builtin-rules etc. just for this makefile (no flag inheritance)

[Kaz Kylheku (gmake)]

On 2020-04-20 03:04, R. Diez wrote:
> Hallo Paul:
>
> I have been investigating Kaz Kylheku's suggestion about adding flags
> to MAKEFLAGS inside the makefile.
>
> I believe that adding --no-builtin-variables has no effect. It is
> probably too late to do that inside the makefile.
>
> That means that option '--no-builtin-rules' does not get automatically
> enabled either.

It can be verified with a minimal Makefile that "make --print-data-base"
shows an absence of built-in rules if MAKEFLAGS += --no-builtin-rules is
present, and likewise that --no-builtin-variables causes the variables
to disappear.

However, environment variables do not disappear. If CC or whatever
is coming down as an environment variable, then of course it stays.

About this other business of calculating a variable inside a recipe
to be used by dependent recipe, the path of least resistance would
be to make it a shell variable.

   base-recipe:
     ...
     heavy-program --option > .base-recipe-var

   dependent-recipe: base-recipe
     VAR=$$(cat .base-recipe-var) ; command $$VAR; ... ; ...

The dependent recipe now just has to read a file rather than execute
heavy-program.

If the datum is small enough, it could be stored in a symlink. Symlinks
whose targets are small enough are stored entirely in the inode 
structure
by some Unix-like file systems.

   base-recipe:
     ...
     ln -sf (heavy-program --show-important-path) .base-recipe-symlink

If the datum is a path, that symlink could be used directly:

   dependent-recipe: base-recipe
     IMPORTANT_PATH=.base-recipe-symlink ; command $$IMPORTANT_PATH ; 
...

Or it could be resolved, if the commands need the original item:

   dependent-recipe: base-recipe
     IMPORTANT_PATH=$(readlink .base-recipe-symlink) ; command 
$$IMPORTANT_PATH ; ...