The Source Integrity Professional Edition User Guide - MKS

Here is another example, this time of a makefile employing
metarules.
Using Inference Rules
FILES = main myFunc
# notice the use of the $E macro representing
# the executable file extension
program$E : $(FILES:+$O)
$(CC) $(CFLAGS) -e$@ $&
%$O : %.c
$(CC) -c $(CFLAGS) $<
When MKS Make attempts to rebuild program$E (here the
predefined E macro represents the executable file extension for your
system), it checks the two specified object files to see if they, in turn,
require rebuilding.
MKS Make notes that these files end in the object file extension for
your system, by expanding the O macro. Since these files lack a
particular rule that names them as targets, MKS Make subsequently
checks for any matching metarule. The metarule (the second rule in
the makefile) does match the object file names, so it is used to rebuild
the object files.
Employing the metarule, MKS Make looks for the object files’
matching source files (which end in a .c extension), and runs them
through the compiler.
Note the lack of specific reference to any object file in this makefile.
MKS Make infers the appropriate object files by expanding
$(FILES:+$O), and uses the metarule to match object files with their
associated source.
Here is another example, one that demonstrates the use of another
common metarule.
% .PRECIOUS : rcs/%$V
-co -q $<
The metarule states that any target (file) depends upon a prerequisite
(an associated archive file) located in an rcs subdirectory. MKS Make
matches any archive file to its associated working file. The recipe line
uses the $< runtime macro to represent the prerequisite matching the
target. Notice that it uses the dash command prefix. MKS Make
ignores the failure of the check out (co) command (as it should, for
example, if a revision of the file has already been checked out).
Also, notice that it uses a macro called V to represent the possible
archive file extension for the archive file. On UNIX-based systems,
archive files usually end with a ,v extension. On PC-based systems,
User Guide 283