make.html

unix 下的C开发手册,还用详细的例程。

<b>SHELL</b>
macro is treated specially.
It is provided by
<i>make</i>
and set to the pathname of the shell command language
interpreter (see
<i><a href="sh.html">sh</a></i>).
The
<i>SHELL</i>
environment variable
will not affect the value of the
<b>SHELL</b>
macro.
If
<b>SHELL</b>
is defined in the makefile or is
specified on the command line, it will replace the original value
of the
<b>SHELL</b>
macro, but will not affect the
<i>SHELL</i>
environment variable.
Other effects of defining
<b>SHELL</b>
in the makefile or on the command line are implementation-dependent.
<h5><a name = "tag_001_014_1377_005">&nbsp;</a>Inference Rules</h5>
<xref type="5" name="infrules"></xref>
Inference rules are formatted as follows:
<pre>
<code>
<i>target</i>:
&lt;tab&gt;<i>command
</i><b>[</b>&lt;tab&gt;<i>command</i><b>]
...

</b><i>line that does not begin with </i>&lt;tab&gt;<i> or </i>#
</code>
</pre>
<p>
The
<i>target</i>
portion must be a valid target name (see
<xref href=mktarg><a href="#tag_001_014_1377_003">
Target Rules
</a></xref>)
of the form
<i>.s2</i>
or
<i>.s1.s2</i>
(where
<i>.s1</i>
and
<i>.s2</i>
are suffixes that have been given as prerequisites of the
<b>.SUFFIXES</b>
special target and
<i>s1</i>
and
<i>s2</i>
do not contain any slashes or periods.)
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.
Inference rules can have only one target before the colon.
<p>
The makefile must not specify prerequisites for inference rules;
no characters other than white space can follow the colon
in the first line,
except when creating the
<i>empty rule,</i>
described below.
Prerequisites are inferred, as described below.
<p>
Inference rules can be redefined.
A target that matches an existing
inference rule will overwrite the old inference rule.
An empty rule can be created with a command
consisting of simply a semicolon
(that is, the rule still exists and is found during inference rule
search, but since it is empty, execution has no effect).
The empty rule also can be formatted as follows:
<pre>
<code>
<i>rule</i>: ;
</code>
</pre>
where zero or more
blank characters
separate the colon and semicolon.
<p>
The
<i>make</i>
utility uses the suffixes of targets and their prerequisites to infer
how a target can be made up-to-date.
A list of inference rules
defines the commands to be executed.
By default,
<i>make</i>
contains a built-in set of inference rules.
Additional rules can be specified in the
makefile.
<p>
The special target
<b>.SUFFIXES</b>
contains as its prerequisites a
list of suffixes that are to be used by the inference rules.
The order in which the suffixes are specified defines the order
in which the inference rules for the suffixes are used.
New suffixes will be appended to the current list by specifying a
<b>.SUFFIXES</b>
special target in the
makefile.
A
<b>.SUFFIXES</b>
target with no
prerequisites will clear the list of suffixes.
An empty
<b>.SUFFIXES</b>
target followed by a new
<b>.SUFFIXES</b>
list is required to change the order of the suffixes.
<p>
Normally, the user would provide an inference rule for each suffix.
The inference rule to update a target with a suffix
<i>.s1</i>
from a prerequisite with a suffix
<i>.s2</i>
is specified as a target
<i>.s2.s1</i>.
The internal macros provide the means to specify general inference rules.
(See
<xref href=mkimacs><a href="#tag_001_014_1377_007">
Internal Macros
</a></xref>.)
<p>
When no target rule is found to update a target, the inference
rules are checked.
The suffix of the target
(<i>.s1</i>)
to be built is compared to the list of suffixes specified by the
<b>.SUFFIXES</b>
special targets.
If the
<i>.s1</i>
suffix is found in
<b>.SUFFIXES</b>,
the inference rules are searched in the order defined for the first
<i>.s2.s1</i>
rule whose prerequisite file
(<b>$*</b><i>.s2</i>)
exists.
If the target is out-of-date with
respect to this prerequisite, the commands for that inference rule
are executed.
<p>
If the target to be built does not contain a suffix and
there is no rule for the target, the single
suffix inference rules will be checked.
The single-suffix inference rules define how to build
a target if a file is found with a name that
matches the target name with one of the single
suffixes appended.
A rule with one suffix
<i>.s2</i>
is the definition of how to build
<i>target</i>
from
<i>target.s2</i>.
The other suffix
(<i>.s1</i>)
is treated as null.
<p>
A tilde
(~)
in the above rules refers to an SCCS file in the current directory.
Thus, the rule
<b>.c~.o</b>
would transform an SCCS C-language source file into an
object file
(<b>.o</b>).
Because the
<b>s.</b>
of the SCCS files is a prefix,
it is incompatible with
<i>make</i>'s
suffix point of view.
Hence, the  ~ is a way of changing any file
reference into an SCCS file reference.
<h5><a name = "tag_001_014_1377_006">&nbsp;</a>Libraries</h5>
If a target or prerequisite contains parentheses, it will be treated
as a member of an archive library.
For the <i>lib</i><b>(</b><i>member</i><b>.o)</b> expression
<i>lib</i>
refers to the name of the archive library and
<i>member</i>.o
to the member name.
The member must be an object file with the
<b>.o</b>
suffix.
The modification time of the expression is the modification time
for the member as kept in the archive library.
See
<i><a href="ar.html">ar</a></i>.
The
<b>.a</b>
suffix refers to an archive library.
The
<i>.s2</i><b>.a</b>
rule is used
to update a member in the library from a file with a suffix
<i>.s2</i>.
<h5><a name = "tag_001_014_1377_007">&nbsp;</a>Internal Macros</h5>
<xref type="5" name="mkimacs"></xref>
The
<i>make</i>
utility maintains five internal macros that can
be used in target and inference rules.
In order to clearly
define the meaning of these macros, some clarification of the
terms
<i>target rule</i>,
<i>inference rule</i>,
<i>target</i>
and
<i>prerequisite</i>
is necessary.
<p>
Target rules are specified by the user in a makefile for a
particular target.
Inference rules are user- or
<i>make</i>-specified
rules for a particular class of target names.
Explicit prerequisites are those prerequisites
specified in a makefile on target lines.
Implicit prerequisites are those prerequisites
that are generated when inference rules are used.
Inference rules are applied to implicit prerequisites or to explicit
prerequisites that do not have target rules defined for them in
the makefile.
Target rules are applied to targets specified in the makefile.
<p>
Before any target in the makefile is updated, each of its
prerequisites (both explicit and implicit) will be updated.
This is accomplished by recursively processing each prerequisite.
Upon recursion, each prerequisite becomes a target itself.
Its prerequisites in turn
are processed recursively until a target is found that has no
prerequisites, at which point the recursion stops.
The recursion then backs up, updating each target as it goes.
<p>
In the definitions that follow, the word
<i>target</i>
refers to one of:
<ul>
<p>
<li>
a target specified in the makefile
<p>
<li>
an explicit prerequisite specified in the
makefile that becomes the target when
<i>make</i>
processes it during recursion
<p>
<li>
an implicit prerequisite that becomes a target when
<i>make</i>
processes it during recursion.
<p>
</ul>
<p>
In the definitions that follow, the word
<i>prerequisite</i>
refers to one o the following:
<ul>
<p>
<li>
an explicit prerequisite specified in the makefile
for a particular target
<p>
<li>
an implicit prerequisite
generated as a result of locating an appropriate inference rule
and corresponding file that matches the suffix of the target.
<p>
</ul>
<br>
<p>
The five internal macros are:
<dl compact>

<dt>$@<dd>The $@ evaluates to the full target name
of the current target, or the archive filename
part of a library archive target.
It is evaluated for both target and inference rules.

For example, in the
<b>.c.a</b>
inference rule, $@ represents the out-of-date
<b>.a</b>
file to be built.
Similarly, in a makefile target rule to build
<b>lib.a</b>
from
<b>file.c</b>,
$@ represents the out-of-date
<b>lib.a</b>.

<dt>$%<dd>The $% macro is evaluated only when the current
target is an archive library member of the form
<i>libname</i>(<i>member</i><b>.o</b>).
In these cases, $@ evaluates to
<i>libname</i>
and $%
evaluates to
<i>member</i><b>.o</b>.
The $% macro is evaluated for both target and inference rules.

For example, in a makefile target rule to build
<b>lib.a(file.o)</b>,
$% represents
<b>file.o</b>
 as opposed to $@, which represents
<b>lib.a</b>.

<dt>$?<dd>The $? macro evaluates to the list of
prerequisites that are newer than the current target.
It is evaluated for both target and inference rules.

For example, in a makefile target rule to build
<b>prog</b>
from
<b>file1.o</b>,
<b>file2.o</b>
and
<b>file3.o</b>,
and where
<b>prog</b>
is not out of date with respect to
<b>file1.o</b>,
but is out of date with respect to
<b>file2.o</b>
and
<b>file3.o</b>,
$? represents
<b>file2.o</b>
and
<b>file3.o</b>.

<dt>$&lt;<dd>In an inference rule, $&lt; evaluates to the filename
whose existence allowed the inference rule to be chosen for the target.
In the
<b>.DEFAULT</b>
rule, the $&lt; macro evaluates to the current target name.
The $&lt; macro is evaluated only for inference rules.

For example, in the
<b>.c.a</b>
inference rule, $&lt; represents the prerequisite
<b>.c</b>
file.

<dt>$*<dd>The $* macro evaluates to the current target
name with its suffix deleted.
It is evaluated at least for inference rules.

For example, in the
<b>.c.a</b>
inference rule, $*.o represents the out-of-date
<b>.o</b>
file that corresponds to the prerequisite
<b>.c</b>
file.

</dl>
<p>
Each of the internal macros has an alternative form.
When an upper-case
D
or
F
is appended to any of the macros, the meaning
is changed to the
<i>directory part</i>
for
D
and
<i>filename part</i>
for
F.
The directory part is the path prefix of the file without a trailing slash;
for the current directory, the directory part is &quot;.&quot;.
When the $? macro contains more than one prerequisite filename, the
$(?D)
and
$(?F)
(or
${?D}
and
${?F})
macros expand to a list of directory name
parts and filename parts respectively.
<p>
For the target <i>lib</i><b>(</b><i>member</i><b>.o)</b> and the
<b>s2.a</b>
rule, the internal macros are defined as:
<dl compact>

<dt>$&lt;<dd><i>member</i><b>.s2</b>

<dt>$*<dd><i>member</i>

<dt>$@<dd><i>lib</i>

<dt>$?<dd><i>member</i><b>.s2</b>

<dt>$%<dd><i>member</i><b>.o</b>

</dl>
<h5><a name = "tag_001_014_1377_008">&nbsp;</a>Default Rules</h5>
<xref type="5" name="mkdefr"></xref>
The default rules for
<i>make</i>
achieve results that are the same
as if the following were used.
Implementations that do not support
FORTRAN may omit
<b>FC</b>,
<b>FFLAGS</b>
and the
.f
inference rules.
Implementations may provide additional macros and rules.
<pre>
<code>
<i>SPECIAL TARGETS</i>

.SCCS_GET: sccs $(SCCSFLAGS) get $(SCCSGETFLAGS) $@     

.SUFFIXES: .o .c .y .l .a .sh .f .c~ .y~ .l~ .sh~ .f~      

<i>MACROS</i>

MAKE=make
AR=ar
ARFLAGS=-rv
YACC=yacc
YFLAGS=
LEX=lex
LFLAGS=
LDFLAGS=
CC=c89
CFLAGS=-O
FC=fort77
FFLAGS=-O 1
GET=get
GFLAGS=
SCCSFLAGS=
SCCSGETFLAGS=-s

<i>SINGLE SUFFIX RULES</i>

.c: