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(autoconf.info)Package Options

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Choosing Package Options
========================

   If a software package has optional compile-time features, the user
can give `configure' command line options to specify whether to compile
them.  The options have one of these forms:

     --enable-FEATURE[=ARG]
     --disable-FEATURE

   These options allow users to choose which optional features to build
and install.  `--enable-FEATURE' options should never make a feature
behave differently or cause one feature to replace another.  They
should only cause parts of the program to be built rather than left out.

   The user can give an argument by following the feature name with `='
and the argument.  Giving an argument of `no' requests that the feature
_not_ be made available.  A feature with an argument looks like
`--enable-debug=stabs'.  If no argument is given, it defaults to `yes'.
`--disable-FEATURE' is equivalent to `--enable-FEATURE=no'.

   `configure' scripts do not complain about `--enable-FEATURE' options
that they do not support.  This behavior permits configuring a source
tree containing multiple packages with a top-level `configure' script
when the packages support different options, without spurious error
messages about options that some of the packages support.  An
unfortunate side effect is that option spelling errors are not
diagnosed.  No better approach to this problem has been suggested so
far.

   For each optional feature, `configure.in' should call
`AC_ARG_ENABLE' to detect whether the `configure' user asked to include
it.  Whether each feature is included or not by default, and which
arguments are valid, is up to you.

 - Macro: AC_ARG_ENABLE (FEATURE, HELP-STRING [, ACTION-IF-GIVEN [,
          ACTION-IF-NOT-GIVEN]])
     If the user gave `configure' the option `--enable-FEATURE' or
     `--disable-FEATURE', run shell commands ACTION-IF-GIVEN.  If
     neither option was given, run shell commands ACTION-IF-NOT-GIVEN.
     The name FEATURE indicates an optional user-level facility.  It
     should consist only of alphanumeric characters and dashes.

     The option's argument is available to the shell commands
     ACTION-IF-GIVEN in the shell variable `enableval', which is
     actually just the value of the shell variable `enable_FEATURE',
     with any `-' characters changed into `_'.  You may use that
     variable instead, if you wish.  The HELP-STRING argument is like
     that of `AC_ARG_WITH' (Note: External Software).

 - Macro: AC_ENABLE (FEATURE, ACTION-IF-GIVEN [, ACTION-IF-NOT-GIVEN])
     This is an obsolete version of `AC_ARG_ENABLE' that does not
     support providing a help string.