Roland Ver. 4.5 Informações Técnicas descarregar pdf (Página 135)

Chapter 10: Using Implicit Rules 125

new rule is deﬁned, the built-in one is replaced. The new rule’s position in the sequence of

implicit rules is determined by where you write the new rule.

You can cancel a built-in implicit rule by deﬁning a pattern rule with the same target

and prerequisites, but no recipe. For example, the following would cancel the rule that runs

the assembler:

%.o : %.s

10.6 Deﬁning Last-Resort Default Rules

You can deﬁne a last-resort implicit rule by writing a terminal match-anything pattern rule

with no prerequisites (see Section 10.5.5 [Match-Anything Rules], page 123). This is just

like any other pattern rule; the only thing special about it is that it will match any target.

So such a rule’s recipe is used for all targets and prerequisites that have no recipe of their

own and for which no other implicit rule applies.

For example, when testing a makeﬁle, you might not care if the source ﬁles contain real

data, only that they exist. Then you might do this:

%::

touch $@

to cause all the source ﬁles needed (as prerequisites) to be created automatically.

You can instead deﬁne a recipe to be used for targets for which there are no rules at

all, even ones which don’t specify recipes. You do this by writing a rule for the target

.DEFAULT. Such a rule’s recipe is used for all prerequisites which do not appear as targets

in any explicit rule, and for which no implicit rule applies. Naturally, there is no .DEFAULT

rule unless you write one.

If you use .DEFAULT with no recipe or prerequisites:

.DEFAULT:

the recipe previously stored for .DEFAULT is cleared. Then make acts as if you had never

deﬁned .DEFAULT at all.

If you do not want a target to get the recipe from a match-anything pattern rule or

.DEFAULT, but you also do not want any recipe to be run for the target, you can give it an

empty recipe (see Section 5.9 [Deﬁning Empty Recipes], page 57).

You can use a last-resort rule to override part of another makeﬁle. See Section 3.6

[Overriding Part of Another Makeﬁle], page 15.

10.7 Old-Fashioned Suﬃx Rules

Suﬃx rules are the old-fashioned way of deﬁning implicit rules for make. Suﬃx rules are

obsolete because pattern rules are more general and clearer. They are supported in GNU

make for compatibility with old makeﬁles. They come in two kinds: double-suﬃx and

single-suﬃx.

A double-suﬃx rule is deﬁned by a pair of suﬃxes: the target suﬃx and the source

suﬃx. It matches any ﬁle whose name ends with the target suﬃx. The corresponding

implicit prerequisite is made by replacing the target suﬃx with the source suﬃx in the ﬁle

name. A two-suﬃx rule whose target and source suﬃxes are ‘.o’ and ‘.c’ is equivalent to

the pattern rule ‘%.o : %.c’.

1 2 ... 130 131 132 133 134 135 136 137 138 139 140 ... 211 212

Sem comentários

Roland Ver. 4.5 Informações Técnicas Página 135