Re: substitution vs expansion in Makefile.am

[John Calcote]

Erik,

I believe I understand Harlan's method. My understanding is that make
actually prefixes all targets not found relative to the current
directory with each path (relative or absolute) specified in VPATH,
until it finds the file (or not). To use my original example, here's
my directory structure:

    project
        common
            mySleep.c
        server
            registrar.c
        dbg-build
            common
            server
                Makefile <--

The dbg-build directory is one I created from which to build a debug
version of my code. The indicated Makefile contains:

    VPATH=../../server

    registrarTest_SOURCES = registrar.c ../common/mySleep.c

Of course, make is able to find registrar.c in project/server because
of the VPATH. It didn't find it in the current directory, so it looked
(effectively) in $(VPATH)/registrar.c. Obviously VPATH is more than
just a variable, but I'm using it in this manner here for the sake of
illustration, because it contains only one component.

But what about mySleep.c? Well it works the same way. It doesn't find
../common/mySleep.c relative to the current directory, so it looks in
$(VPATH)/../common/mySleep.c, which resolves to
../../server/../common/mySleep.c, which finally resolves to
../../common/mySleep.c.

hth
John


Harlan Stenn wrote:

> > You can use: ../common/mySleep.c in your foo_SOURCES list.

If the sources are in /home/user/src and you go to /home/usr/build
and do "../src/configure" the above will be completely wrong.

The correct way to do it is to use "$(top_srcdir)/common/mySleep.c"
which will work under all circumstances.

Erik

On Tue, Mar 4, 2008 at 4:29 PM, Harlan Stenn <address@hidden> wrote:
> John,
>
>
>  > Bob, server/Makefile's VPATH only contains the expansion of
>  > @top_srcdir@/server, which in this case is ../../server. This means
>  > that make won't be able to find any sources listed that exist in
>  > directories other than ../../server. So I think I HAVE to use
>  > $(top_srcdir)/common/mySleep.c, don't I, as it's in a different source
>  > directory?
>
>  You can use: ../common/mySleep.c in your foo_SOURCES list.
>
>  H
>