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of The GNU Make Manual, for GNU make version 3.81.
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<title>GNU make: 13. Incompatibilities and Missing Features</title>
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<h1 class="chapter"> 13. Incompatibilities and Missing Features </h1>
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<p>The <code>make</code> programs in various other systems support a few features
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that are not implemented in GNU <code>make</code>. The POSIX.2 standard
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(<cite>IEEE Standard 1003.2-1992</cite>) which specifies <code>make</code> does not
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require any of these features.
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A target of the form ‘<samp><var>file</var>((<var>entry</var>))</samp>’ stands for a member
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of archive file <var>file</var>. The member is chosen, not by name, but by
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being an object file which defines the linker symbol <var>entry</var>.
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<p>This feature was not put into GNU <code>make</code> because of the
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nonmodularity of putting knowledge into <code>make</code> of the internal
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format of archive file symbol tables.
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See section <a href="make_11.html#SEC131">Updating Archive Symbol Directories</a>.
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Suffixes (used in suffix rules) that end with the character ‘<samp>~</samp>’
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have a special meaning to System V <code>make</code>;
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they refer to the SCCS file that corresponds
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to the file one would get without the ‘<samp>~</samp>’. For example, the
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suffix rule ‘<samp>.c~.o</samp>’ would make the file ‘<tt><var>n</var>.o</tt>’ from
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the SCCS file ‘<tt>s.<var>n</var>.c</tt>’. For complete coverage, a whole
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series of such suffix rules is required.
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See section <a href="make_10.html#SEC126">Old-Fashioned Suffix Rules</a>.
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<p>In GNU <code>make</code>, this entire series of cases is handled by two
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pattern rules for extraction from SCCS, in combination with the
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general feature of rule chaining.
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See section <a href="make_10.html#SEC117">Chains of Implicit Rules</a>.
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In System V and 4.3 BSD <code>make</code>, files found by <code>VPATH</code> search
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(see section <a href="make_4.html#SEC38">Searching Directories for Prerequisites</a>) have their names changed inside command
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strings. We feel it is much cleaner to always use automatic variables
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and thus make this feature obsolete.
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In some Unix <code>make</code>s, the automatic variable <code>$*</code> appearing in
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the prerequisites of a rule has the amazingly strange “feature” of
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expanding to the full name of the <em>target of that rule</em>. We cannot
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imagine what went on in the minds of Unix <code>make</code> developers to do
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this; it is utterly inconsistent with the normal definition of <code>$*</code>.
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In some Unix <code>make</code>s, implicit rule search
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(see section <a href="make_10.html#SEC113">Using Implicit Rules</a>) is apparently done for
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<em>all</em> targets, not just those without commands. This means you can
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<table><tr><td> </td><td><pre class="example">foo.o:
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</pre></td></tr></table>
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<p>and Unix <code>make</code> will intuit that ‘<tt>foo.o</tt>’ depends on
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‘<tt>foo.c</tt>’.
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<p>We feel that such usage is broken. The prerequisite properties of
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<code>make</code> are well-defined (for GNU <code>make</code>, at least),
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and doing such a thing simply does not fit the model.
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GNU <code>make</code> does not include any built-in implicit rules for
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compiling or preprocessing EFL programs. If we hear of anyone who is
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using EFL, we will gladly add them.
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It appears that in SVR4 <code>make</code>, a suffix rule can be specified with
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no commands, and it is treated as if it had empty commands
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(see section <a href="make_5.html#SEC73">Using Empty Commands</a>). For example:
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<table><tr><td> </td><td><pre class="example">.c.a:
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</pre></td></tr></table>
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<p>will override the built-in ‘<tt>.c.a</tt>’ suffix rule.
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<p>We feel that it is cleaner for a rule without commands to always simply
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add to the prerequisite list for the target. The above example can be
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easily rewritten to get the desired behavior in GNU <code>make</code>:
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<table><tr><td> </td><td><pre class="example">.c.a: ;
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</pre></td></tr></table>
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Some versions of <code>make</code> invoke the shell with the ‘<samp>-e</samp>’ flag,
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except under ‘<samp>-k</samp>’ (see section <a href="make_9.html#SEC111">Testing the Compilation of a Program</a>). The ‘<samp>-e</samp>’ flag tells the shell to exit as soon as any
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program it runs returns a nonzero status. We feel it is cleaner to
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write each shell command line to stand on its own and not require this
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