autoconf: Package Options

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1 15.3 Choosing Package Options
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1 If a software package has optional compile-time features, the user can
1 give `configure' command line options to specify whether to compile
1 them.  The options have one of these forms:
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1      --enable-FEATURE[=ARG]
1      --disable-FEATURE
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1    These options allow users to choose which optional features to build
1 and install.  `--enable-FEATURE' options should never make a feature
1 behave differently or cause one feature to replace another.  They
1 should only cause parts of the program to be built rather than left out.
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1    The user can give an argument by following the feature name with `='
1 and the argument.  Giving an argument of `no' requests that the feature
1 _not_ be made available.  A feature with an argument looks like
1 `--enable-debug=stabs'.  If no argument is given, it defaults to `yes'.
1 `--disable-FEATURE' is equivalent to `--enable-FEATURE=no'.
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1    Normally `configure' scripts complain about `--enable-PACKAGE'
1 options that they do not support.  ⇒Option Checking, for
1 details, and for how to override the defaults.
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1    For each optional feature, `configure.ac' should call
1 `AC_ARG_ENABLE' to detect whether the `configure' user asked to include
1 it.  Whether each feature is included or not by default, and which
1 arguments are valid, is up to you.
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1  -- Macro: AC_ARG_ENABLE (FEATURE, HELP-STRING, [ACTION-IF-GIVEN],
1           [ACTION-IF-NOT-GIVEN])
1      If the user gave `configure' the option `--enable-FEATURE' or
1      `--disable-FEATURE', run shell commands ACTION-IF-GIVEN.  If
1      neither option was given, run shell commands ACTION-IF-NOT-GIVEN.
1      The name FEATURE indicates an optional user-level facility.  It
1      should consist only of alphanumeric characters, dashes, plus
1      signs, and dots.
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1      The option's argument is available to the shell commands
1      ACTION-IF-GIVEN in the shell variable `enableval', which is
1      actually just the value of the shell variable named
1      `enable_FEATURE', with any non-alphanumeric characters in FEATURE
1      changed into `_'.  You may use that variable instead, if you wish.
11      The HELP-STRING argument is like that of `AC_ARG_WITH' (⇒
      External Software).
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1      You should format your HELP-STRING with the macro `AS_HELP_STRING'
1      (⇒Pretty Help Strings).
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1      See the examples suggested with the definition of `AC_ARG_WITH'
1      (⇒External Software) to get an idea of possible
1      applications of `AC_ARG_ENABLE'.
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