z/OS V1R9.0 UNIX System Services Command ... - Christian Grothoff

Order of Rule Generation
Since transitive closure allows make to generate new rules, it is important to
understand the order in which this is done:
Suffix Rules
1. make searches for explicit rules in the order in which they appear, so explicit
rules always take precedence.
2. make reads metarules in the order in which they appear in the makefile. The
first rule that appears in the makefile is the first one checked.
3. New explicit metarules (as distinct from metarules generated by transitive
closure) replace old ones. In other words, if your makefile contains an explicit
rule like this one, it replaces the default rule in startup.mk:
%$O : %.c
rule1
If you use the –v option, make prints a warning when it replaces a metarule.
4. When transitive closure is calculated, the new metarules generated are added
to the end of the list of possible metarules. Thus, make always finds the explicit
rules first, so they take precedence over generated rules. You can use the –v
option to see what rules make generates and the order in which they appear.
5. make performs two passes through the rules. On the first pass it tries to find a
match with an explicit rule in the makefile; if this does not succeed, make
performs a second pass to find a match with an existing file.
make treats targets that begin with a period and contain no slashes or percent
signs as suffix rules. If there is only one period in the target, it is a single suffix
inference rule. Targets with two periods are double-suffix inference rules. Suffix
rules do not have prerequisites but do have commands associated with them.
When make finds no explicit rule to update a target, it checks the suffix of the
target (.s1) to be built against the suffix rules. make examines a prerequisite based
on the basename of the target with the second suffix (.s2) appended, and if the
target is out of date with respect to this prerequisite, make runs the recipe for that
inference rule.
Metarules take precedence over suffix rules.
If the target to be built does not contain a suffix and there is no rule for the target,
make checks the single suffix inference rules. The single suffix inference rules
define how to build a target if make finds a rule with one of the single suffixes
appended. A rule with one suffix .s2 defines how to build target from target.s2.
make treats the other suffix (.s1) as null.
For a suffix rule to work, the component suffixes must appear in the prerequisite list
of the .SUFFIXES special target. You can turn off suffix rules by placing the following
in your makefile:
.SUFFIXES:
This clears the prerequisites of the .SUFFIXES target, which prevents suffix rules
from being enacted. The order that the suffixes appear in the .SUFFIXES rule
determines the order in which make checks the suffix rules.
The search algorithm used for suffix rules depends on whether the .POSIX special
target is specified. When .POSIX is specified, the following steps describe the
search algorithm for suffix rules:
make
Chapter 2. Shell command descriptions 401