The Source Integrity Professional Edition User Guide - MKS

Using the MKS Make Utility
For more information on this
process, see the man page for
the make command.
Suffix Rules
If the object file for the executable does not exist, transitive closure
allows MKS Make to infer that it needs to first build the required
object file from source, using this newly generated rule.
When MKS Make finishes the computation for the rule head, it marks
that rule head as transitive closure completed. Since it adds all
possible new rules to the rule set the first time it performs the
computation, MKS Make will not compute transitive closure again;
nothing new can be added to the rule set.
To understand this process best, you might want to experiment on
small makefiles, using the -v option to the make command. This
displays the behavior in detail: which rules it searches, when it
computes transitive closure, and which rules it adds to the set.
MKS Make follows a particular order when attempting to make
inferences.
An older portable form of inference rules, suffix rules use the format
# typical suffix rule
.suf1.suf2:
recipe
MKS Make matches the suffixes against the suffix of a target when it
cannot locate an explicit rule for that target. However, suffix rules are
not as powerful or as intuitive as metarules.
For example, to express the dependence of object files upon source
files, you would need a suffix rule that looked like
.c$O:
$(CC) -c $(CFLAGS) $<
Compare this with the equivalent metarule.
# normal rule
file$O : file.c
$(CC) -c $(CFLAGS) file.c
# metarule
%$O : %.c
$(CC) -c $(CFLAGS) $<
You can see that the construction of the suffix rule seems backwards.
By itself, this gives a good reason to avoid suffix rules; you will find
makefiles with suffix rules much more difficult to read.
286 Source Integrity Professional Edition