Re: Getting the target of an implicit rule within the rule

[Ronald Landheer-Cieslak]

Paul D. Smith wrote:

> %% Ronald Landheer-Cieslak <address@hidden> writes:
>
>   rl> %.d : $(srcdir)/$(subst .d,.c,$@)
>   rl>       blah
>
>   rl> $@, however, is empty here (as the docs duely indicate).
>
>   >> Why not just use the obvious:
>   >> 
>   >> %.d : $(srcdir)/%.c
>
>   rl> because the obvious doesn't work if there's a pathname in the
>   rl> target filename (i.e. target == dir/file.d, prereq would become
>   rl> dir/$(srcdir)/file.c because the stem of the pattern is "file",
>   rl> not "dir/file").
>
> Well sure, that won't work, but that's not the example you gave.  It's
> hard to give solutions that work for examples that are not provided :).
OK, let me just give you a wee bit of background, then:

I have a single, partly-generated Makefile that will make entire source 
tree. It is generated by a bootstrap & configure script in two steps: 
Makefile.in.in > (bootstrap) > Makefile.in > (configure) > Makefile
The contents of each is available at 
http://cvs.sf.net/viewcvs.py/jail-ust/config/ with the Makefile.in.in 
itself at 
http://cvs.sf.net/viewcvs.py/jail-ust/config/Makefile.in.in?view=markup

The number of subdirectories to make is variable, so I can't just 
pre-write the rules for each: I want to reduce the re-writing to be done 
for each new module (directory) to the first line on which I enumerate 
them all as bootstrap-replaced variables.

The idea of the setup is that you can do
$ bash bootstrap
$ mkdir .build && cd .build
$ ../configure
$ make

and compile everything in one go, without recursive makes.

The reason for not using recursive makes is double: maintainability and 
make time. Maintainability because I only have to maintain a module.mk 
file per directory, to which I just add the name of a source file 
whenever there's a new source file. Speed of make for the reasons 
stipulated in 
http://cvs.sf.net/viewcvs.py/*checkout*/jail-ust/doc/auug97.pdf

Sorry about not giving this background in the original post: I guess I 
snipped it when I weeded out the "unnecessary" details :(

> Typically what I do is not try to install the srcdir inside the
> pathname but rather have it at the top.  If you have to put it inside
> you'll have to write a different rule for each value of "dir".  You
> can use $(eval ...) (in the newest releases of GNU make) to do this
> without typing it all out.
Now *there's* an idea!

I hadn't gotten around to linking my libraries yet, because I hadn't 
figured out a way to do it generically, but $(eval ...) just might do 
the trick - thanks :)

rlc