3.4. Target Attributes

This attribute causes its shell script to be executed while having no effect on targets that depend on it. This makes the target into a sort of subroutine. An example. Say you have some LISP files that need to be compiled and loaded into a LISP process. To do this, you echo LISP commands into a file and execute a LISP with this file as its input when everything is done. Say also that you have to load other files from another system before you can compile your files and further, that you do not want to go through the loading and dumping unless one of your files has changed. Your makefile might look a little bit like this (remember, this is an educational example, and do not worry about the COMPILE rule, all will soon become clear, grasshopper):

system          : init a.fasl b.fasl c.fasl
	for i in $(.ALLSRC);
	do
		echo -n '(load "' >> input
		echo -n ${i} >> input
		echo '")' >> input
	done
	echo '(dump "$(.TARGET)")' >> input
	lisp < input

a.fasl          : a.l init COMPILE
b.fasl          : b.l init COMPILE
c.fasl          : c.l init COMPILE
COMPILE         : .USE
	echo '(compile "$(.ALLSRC)")' >> input
init            : .EXEC
	echo '(load-system)' > input

This allows you to specify one target as a source for another without the one affecting the other's local variables. Useful if, say, you have a makefile that creates two programs, one of which is used to create the other, so it must exist before the other is created. You could say

prog1           : $(PROG1OBJS) prog2 MAKEINSTALL
prog2           : $(PROG2OBJS) .INVISIBLE MAKEINSTALL

This is another way to avoid performing some operations in parallel while permitting everything else to be done so. Specifically it forces the target's shell script to be executed only if one or more of the sources was out-of-date. In addition, the target's name, in both its .TARGET variable and all the local variables of any target that depends on it, is replaced by the value of its .ALLSRC variable. As an example, suppose you have a program that has four libraries that compile in the same directory along with, and at the same time as, the program. You again have the problem with ranlib that I mentioned earlier, only this time it is more severe: you can not just put the ranlib off to the end since the program will need those libraries before it can be re-created. You can do something like this:

program         : $(OBJS) libraries
	cc -o $(.TARGET) $(.ALLSRC)

libraries       : lib1.a lib2.a lib3.a lib4.a .JOIN
	ranlib $(.OODATE)

The .MAKE attribute marks its target as being a recursive invocation of PMake. This forces PMake to execute the script associated with the target (if it is out-of-date) even if you gave the -n or -t flag. By doing this, you can start at the top of a system and type

pmake -n

By giving a target this attribute, you turn it into PMake's equivalent of a macro. When the target is used as a source for another target, the other target acquires the commands, sources and attributes (except .USE) of the source. If the target already has commands, the .USE target's commands are added to the end. If more than one .USE-marked source is given to a target, the rules are applied sequentially. The typical .USE rule (as I call them) will use the sources of the target to which it is applied (as stored in the .ALLSRC variable for the target) as its “arguments,” if you will. For example, you probably noticed that the commands for creating lib1.a and lib2.a in the example in section Section 3.3 were exactly the same. You can use the .USE attribute to eliminate the repetition, like so:

lib1.a          : $(LIB1OBJS) MAKELIB
lib2.a          : $(LIB2OBJS) MAKELIB

MAKELIB         : .USE
	rm -f $(.TARGET)
	ar cr $(.TARGET) $(.ALLSRC)
	...
	ranlib $(.TARGET)