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Chapter 4: Writing Rules 25

$(wildcard *.c)

We can change the list of C source ﬁles into a list of object ﬁles by replacing the ‘.c’

suﬃx with ‘.o’ in the result, like this:

$(patsubst %.c,%.o,$(wildcard *.c))

(Here we have used another function, patsubst. See Section 8.2 [Functions for String

Substitution and Analysis], page 84.)

Thus, a makeﬁle to compile all C source ﬁles in the directory and then link them together

could be written as follows:

objects := $(patsubst %.c,%.o,$(wildcard *.c))

foo : $(objects)

cc -o foo $(objects)

(This takes advantage of the implicit rule for compiling C programs, so there is no need to

write explicit rules for compiling the ﬁles. See Section 6.2 [The Two Flavors of Variables],

page 60, for an explanation of ‘:=’, which is a variant of ‘=’.)

4.4 Searching Directories for Prerequisites

For large systems, it is often desirable to put sources in a separate directory from the

binaries. The directory search features of make facilitate this by searching several directories

automatically to ﬁnd a prerequisite. When you redistribute the ﬁles among directories, you

do not need to change the individual rules, just the search paths.

4.4.1 VPATH: Search Path for All Prerequisites

The value of the make variable VPATH speciﬁes a list of directories that make should search.

Most often, the directories are expected to contain prerequisite ﬁles that are not in the

current directory; however, make uses VPATH as a search list for both prerequisites and

targets of rules.

Thus, if a ﬁle that is listed as a target or prerequisite does not exist in the current

directory, make searches the directories listed in VPATH for a ﬁle with that name. If a ﬁle is

found in one of them, that ﬁle may become the prerequisite (see below). Rules may then

specify the names of ﬁles in the prerequisite list as if they all existed in the current directory.

See Section 4.4.4 [Writing Recipes with Directory Search], page 27.

In the VPATH variable, directory names are separated by colons or blanks. The order in

which directories are listed is the order followed by make in its search. (On MS-DOS and

MS-Windows, semi-colons are used as separators of directory names in VPATH, since the

colon can be used in the pathname itself, after the drive letter.)

For example,

VPATH = src:../headers

speciﬁes a path containing two directories, src and ../headers, which make searches in

that order.

With this value of VPATH, the following rule,

foo.o : foo.c

is interpreted as if it were written like this:

1 2 ... 30 31 32 33 34 35 36 37 38 39 40 ... 211 212

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Roland Ver. 4.5 Información técnica Pagina 35