Re: Question about use of $(wildcard) and $(foreach)

[Rick Flower]

Mike Shal wrote:
> On 4/16/07, Rick Flower <address@hidden> wrote:
> > I took a different approach and listed all of the possible paths in a
> > variable called "OBJDIRS" and wanted to write some makefile 'code' that
> > could pick out the only one that exists for the directory tree where
> > Make was invoked from.. Below is what I was trying but found that it
> > would only return a valid OBJDIR when the valid directory was at the end
> > of the list (IIRC) or other odd conditions:
> >
> > OBJDIR =
> > OBJDIRS := \
> >            ../../${proc}/obj/${target) \
> >            ../../${target}/obj \
> >            ../../obj/${target}
>
> First: note that you have "${target)" - you should probably use either
> "${target}" or "$(target)", rather than mix and match your parens :).

Hmm.. Good catch.. I hadn't noticed that before.. I think that was one 
of the problems I had..

> > find_files  = $(if $(wildcard $(dir)),OBJDIR=${dir})
> > OBJDIR := $(foreach dir,$(OBJDIRS),$(find_files))
>
> $(wildcard) already operates separately on each element in the list,
> so you don't need to wrap it with a $(foreach) in this case. Also, you
> wouldn't want OBJDIR= in the $(if) statement, since you aren't
> actually executing statements there.
>
> Anyway, this could probably be much simplified by just doing:
>
> OBJDIR := $(firstword $(wildcard $(OBJDIRS)))

I tried that w/o the above fix for the typo in place and it didn't work 
(nor did John's suggestion either).. Once I fixed the typo above to have 
matching open/closing braces then it started working.. I wonder if this 
could be caught during the parsing phase and have an error issued.. I 
certainly didn't see it and it obviously had side effects..

> The $(firstword) is used in case more than one directory exists - this
> would just pick the first one. You probably also want to check if no
> match was found and print an error, like:
>
> ifeq (,$(OBJDIR))
>  $(error No directory found)
> endif

Thanks.. I'll put that catch-all statement in as well.. Thanks again to 
both Mike and John for quick answers!

-- Rick