Re: How to use wildcard for different 'stem' values

[Paul D. Smith]

%% address@hidden writes:

  hpvl> %process/gen.out : $(addprefix %, $(wildcard cmd/*.tcl)) 
  hpvl>         commands... 

As I mentioned before, all variables and functions in target and
prerequisite lists (for all types of rules) are expanded _FIRST_, and
only once, as the makefile is read in.

Patterns are evaluated later, while make is attempting to find rules to
satisfy a target build requirement.

Information on when variables and functions are expanded is available in
the GNU make manual section "How 'make' Reads A Makefile".

So, in the above example $(wildcard cmd/*.tcl) is expanded immediately,
then the prefix "%" is appended to the results of that expansion.

  hpvl> What I would achieve is to have the wildcard command done for
  hpvl> each value of %.  So for each value of % the dependency could be
  hpvl> different.  Does someone know how I can do that?

This is not easy at all.  You will have to have a different explicit
rule for each possible target.  So, you will have to either write them
out by hand or find a way to automatically generate them.

There are two ways to do the latter: the "old" way, which works with
almost any version of GNU make, is to write a rule that generates a
makefile fragment containing the targets you want, then include that
fragment.  GNU make has a special feature where it tries to remake every
included makefile and, if it succeeds, it will re-exec itself to read
that new makefile.

The "new" way is to use the $(eval ...) function, which is only
available in GNU make 3.80, and in that version has some bugs that
require patching (or using the latest source from CVS).

-- 
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