Re: multi-architecture builds and recursive makes

[Paul D. Smith]

%% "Robert P. J. Day" <address@hidden> writes:

  rpjd> i'm reading paul smith's essay on multi-architecture builds
  rpjd> (http://make.paulandlesley.org/multi-arch.html), but it seems
  rpjd> that that approach wouldn't work if one had a recursive make
  rpjd> structure, would it?

Sure.

  rpjd> that is, say one had the source directory SRCDIR and the
  rpjd> directory in which to build the objects OBJDIR, the *general*
  rpjd> form of the make invocation would be (simplified drastically for
  rpjd> brevity):

  rpjd>   $ cd ${SRCDIR}
  rpjd>   $ make -C ${OBJDIR} -f ${SRCDIR}/Makefile <target>

  rpjd> that would work fine for simple targets, but if the Makefile had
  rpjd> a recursive structure that tried to "make" into SRCDIR's
  rpjd> subdirectories, it seems this would fail as the make (running
  rpjd> effectively in OBJDIR) would try to locate the subdirectories in
  rpjd> OBJDIR, not SRCDIR, would fail to find them, and abort, no?  (a
  rpjd> quick test seems to verify this behaviour.)

No...

The model is this: you run the make in the source directory.  That is
sort of the "master" make.  It will invoke a sub-make in the target
directory in order to build all the local targets.

_BUT_, that sub-make doesn't try to build any subdirectories.  Instead,
once the sub-make is done building the local targets it exits.  Then
it's up to the parent make (in the source directory) to run any
sub-makes.


In short, you want to put any recursion into the section of the makefile
that's invoked in the source directory, not the section invoked in the
target directory.

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