Roland Ver. 4.5 Technical Information PDF herunterladen (Seite 30)

20 GNU make

tively. In the third they will have values foo.1, foo.1 bar.1 foo.2 bar.2, and foo.1

bar.1 foo.2 bar.2 foo.1 foo.1 bar.1 foo.1 bar.1 respectively.

Rules undergo secondary expansion in makeﬁle order, except that the rule with the

recipe is always evaluated last.

The variables $$? and $$* are not available and expand to the empty string.

Secondary Expansion of Static Pattern Rules

Rules for secondary expansion of static pattern rules are identical to those for explicit rules,

above, with one exception: for static pattern rules the $$* variable is set to the pattern

stem. As with explicit rules, $$? is not available and expands to the empty string.

Secondary Expansion of Implicit Rules

As make searches for an implicit rule, it substitutes the stem and then performs secondary

expansion for every rule with a matching target pattern. The value of the automatic vari-

ables is derived in the same fashion as for static pattern rules. As an example:

.SECONDEXPANSION:

foo: bar

foo foz: fo%: bo%

%oo: $$< $$^ $$+ $$*

When the implicit rule is tried for target foo, $$< expands to bar, $$^ expands to bar

boo, $$+ also expands to bar boo, and $$* expands to f.

Note that the directory preﬁx (D), as described in Section 10.8 [Implicit Rule Search

Algorithm], page 127, is appended (after expansion) to all the patterns in the prerequisites

list. As an example:

.SECONDEXPANSION:

/tmp/foo.o:

%.o: $$(addsuffix /%.c,foo bar) foo.h

@echo $^

The prerequisite list printed, after the secondary expansion and directory preﬁx recon-

struction, will be /tmp/foo/foo.c /tmp/bar/foo.c foo.h. If you are not interested in this

reconstruction, you can use $$* instead of % in the prerequisites list.

1 2 ... 25 26 27 28 29 30 31 32 33 34 35 ... 211 212

Keine Kommentare

Roland Ver. 4.5 Technical Information Seite 30