# @(#)README.multiarch	1.1 4/15/91

This file describes a scheme for building versions of ups for multiple
different architectures in one NFS mounted source directory.  This is
switched off by default in the distribution.  You probably only want
to look at enabling this if you are doing development work on ups for
multiple architectures.


The ups makefiles have optional support for multi-architecture compilation.
By default they build .o files in the current directory, but if certain
environment variables are set they will drop .o files in subdirectories.
This way you can have parallel builds for different machine architectures
in a single NFS mounted source directory.

To enable the multi-architecture support, you need to ensure that four
make variables are set.  The variables are:

	OBJDIR		a path from this directory to where you want
			.o files to go.

	SRCDIR		path that takes you back from ${OBJDIR} to this
			source directory.
	
	SLASH		set to the single character string `/'.

	IN_OBJDIR	set to 'cd ${OBJDIR} && '

The last two are ugly, but are necessary to make this scheme drop
back to a normal build if no variables are set.

Locally I like to have all object files below a directory obj with
subdirectories for the various machine types.  So on a Sun 4 I have
the following set:

	OBJDIR		"obj/sun4_sunos4"
	SRCDIR		"../.."
	SLASH		"/"
	IN_OBJDIR 	"cd ${OBJDIR} && "

On machines where make imports environment variables you can just
setenv these in your .login file.  If you have a command like Sun's
arch utility you can say something like "setenv OBJDIR obj/`arch`"
and wherever you go the object files will get dropped in the right
place.

This scheme can also be used to keep gcc and cc built object files
separate - I have a makegcc shell script which builds things with gcc.