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From: schaefer@ogcvax.UUCP (Barton E. Schaefer)
Newsgroups: comp.unix.questions
Subject: Re: Using subdirectories from make
Message-ID: <1433@ogcvax.UUCP>
Date: Sat, 26-Sep-87 16:08:21 EDT
Article-I.D.: ogcvax.1433
Posted: Sat Sep 26 16:08:21 1987
Date-Received: Wed, 30-Sep-87 00:56:29 EDT
References: <831@ektools.UUCP> <204@tut.cis.ohio-state.edu> <ihlpm.1413>
Reply-To: schaefer@ogcvax.UUCP (Barton E. Schaefer)
Organization: Oregon Graduate Center, Beaverton, OR
Lines: 43

In article <ihlpm.1413> snafu@ihlpm.ATT.COM (Wallis) writes:
}In article <204@tut.cis.ohio-state.edu>, mdf@tut.cis.ohio-state.edu (Mark D. Freeman) writes:
}>In <831@ektools.UUCP> jim@ektools.UUCP (James Hugh Moore) writes:
}>>... a way of keeping source in one directory and objects in another and
}>>using one makefile.  
}> 
}> I am in need of similar advice.
}> 
}On UNIX, the following should work. I'll base the example on the following
}directory structure ...
}----
}SOURCE_DIR = $(BASE)/src
}INC_DIR = $(BASE)/include
}OBJ_DIR = $(BASE)/obj
} [...]
}$(OBJ_DIR)/foo.o: $(SRC_DIR)/foo.c $(INC_DIR)/hdr.h
}		$(CC) $(CFLAGS) $(SRC_DIR)/foo.c

This works OK, but what if there are several dozen source files and
corresponding objects?  Do you really want to specify every single one of those
dependencies and compilation commands, where the only thing that changes from
line to line is the basename of the file?

The VPATH variable (found in 4.3BSD make, among others) helps a little, but
can't specify different object directories and leaves something to be desired
even in terms of local objects depending on "remote" sources.  For example,
given the dependency

foo : foo.o
	$(CC) $(CFLAGS) foo.o -o foo

where foo.c is in a VPATH-specified directory, the "right " thing happens if
you say "make foo".  But if you type "make foo.o" (which works under the
default ".c.o:" dependency if foo.c is in the same directory) simply does
nothing -- doesn't even complain that it can't make foo.c.

Is there any way to handle this?

-- 
Bart Schaefer			CSNET:	schaefer@Oregon-Grad
				UUCP:	...{tektronix,verdix}!ogcvax!schaefer
"This area is like heaven, and they want to turn it into California."
		-- Joseph Cook, Amish farmer, protesting highway construction