Re: Help needed for writing a rule

On Fri, 2022-11-25 at 15:26 +0100, Patrick Begou wrote:
> How can I write a generic rule for building TOTO_M.mod from
> toto_m.f90 source and put it in the LIB folder ?

There is no way to do this using "straightforward" pattern rules. 
Pattern rules always rely on the stem (the "%" part) being an identical
string (including case) in the target and prerequisite.  That cannot be
changed.

> Of course,the following lines will not work as the "%" token will be
> in uppercase on the right hand side.
> 
> # building only the mod file
> LIB/%_M.mod: %_m.f90
>          @echo "building $*_M.mod"
>          touch $@

The only thing I can think of is to use secondary expansion:

  .SECONDEXPANSION:

  # building only the mod file
  LIB/%_M.mod: $$(shell echo $$* | tr A-Z a-z)_m.f90
          @echo "building $*_M.mod"
          touch $@

Note the doubled-"$" here.

If this doesn't work then it's not possible to create an implicit rule
in your situation and you'll just have to create explicit rules for all
your targets.  You can use a foreach / eval loop to do it if you don't
want to write it all out by hand.