Re: writing a macro to process subdirectories

[John Graham-Cumming]

On Fri, 2005-01-07 at 06:22, Robert P. J. Day wrote:
>   however, reading the make manual, i see an alternative form of
> processing SUBDIRS that i prefer, since it supports parallel
> processing and subdirectory dependencies:
> 
>   SUBDIRS = d1 d2 d3
> 
>   .PHONY: subdirs ${SUBDIRS}
>   subdirs: ${SUBDIRS}
> 
>   ${SUBDIRS}:
>         ${MAKE} -C $@
> 
>   d1: d2              # potential subdir dependency
> 
> but this second form doesn't accommodate a subdirectory target, such
> as "configure" or "clean".

You could achieve this with a target specific variable like this:

  SUBDIRS = d1 d2 d3

  .PHONY: subdirs ${SUBDIRS} clean configure
  subdirs: ${SUBDIRS}

  ${SUBDIRS}:
          ${MAKE} -C $@ $(SUBDIR_GOAL)

  d1: d2                # potential subdir dependency

  clean: subdirs
  clean: SUBDIR_GOAL=clean

  configure: subdirs
  configure: SUBDIR_GOAL=configure

Target specific variables are available in the prereqs of a target so
SUBDIR_GOAL will be set appropriately by the clean and configure targets
and then can be used in the subdirs.

Or if you know that you are only going to use one of these specific
targets like clean or configure on the command-line you could do:

  SUBDIRS = d1 d2 d3

  .PHONY: subdirs ${SUBDIRS} clean configure
  subdirs: ${SUBDIRS}

  ${SUBDIRS}:
          ${MAKE} -C $@ $(MAKECMDGOALS)

  d1: d2                # potential subdir dependency

  clean: subdirs
  configure: subdirs

John.
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John Graham-Cumming

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