On Saturday 05 February 2005 01:01, Gregorio Guidi wrote:
> So I think we should:
>
> for main problem: encourage the use of AC_ARG_WITH and AC_ARG_ENABLE.
>
> for child problem: provide a standard interpretation of those macros
> (either through a macro that standardizes the use of
> AC_ARG_WITH/AC_ARG_ENABLE, such as the ones I posted at the beginning; or
> through some more precise documentation on their use, so that I can point
> to it when interacting with software developers).
I'm coming back to this problem after trying to write something down.
I think there aren't catch-all solutions for the moment, all that can be done
is extending a bit the autoconf documentation with respect to these macros,
maybe adding a few examples for the most common use cases.
Please take a look at the patch below and say what you think.
Note: as you can see, the patch assumes there will be a solution for the
"AC_REQUIRE in shell conditional" issue.
Gregorio
Index: doc/autoconf.texi
===================================================================
RCS file: /cvsroot/autoconf/autoconf/doc/autoconf.texi,v
retrieving revision 1.879
diff -u -B -r1.879 autoconf.texi
--- doc/autoconf.texi 15 Feb 2005 06:40:21 -0000 1.879
+++ doc/autoconf.texi 15 Feb 2005 17:00:23 -0000
@@ -13222,6 +13222,78 @@
You should format your @var{help-string} with the macro
@code{AS_HELP_STRING} (@pxref{Pretty Help Strings}).
+
+The following example shows how to use the @code{AC_ARG_WITH} macro in
+a very common situation. You want to let the user decide whether to enable
+support for an external library (e.g. the readline library); if the user
+did not specify neither @option{--with-readline} nor
+@option{--without-readline}, you want to enable support for readline only
+if the library is available on the system.
+
+@example
+AC_ARG_WITH(readline,
+ AS_HELP_STRING(--with-readline, [support fancy command line editing @@<:@@default=check@@:>@@]), ,
+ with_readline=check)
+LIBREADLINE=
+if test "x$with_readline" != xno; then
+ AC_CHECK_LIB(readline, main,
+ [
+ LIBREADLINE="-lreadline -lncurses"
+ AC_DEFINE_UNQUOTED(HAVE_LIBREADLINE, 1, [Define if you have libreadline])
+ ],[
+ if test "x$with_readline" != xcheck; then
+ AC_MSG_FAILURE([--with-readline was given, but test for readline failed])
+ fi
+ ], -lncurses)
+fi
+AC_SUBST(LIBREADLINE)
+@end example
+
+The next example shows how to use @code{AC_ARG_WITH} to give the user the
+possibility to enable support for the readline library, in case it is still
+experimental and not well tested, and is therefore disabled by default.
+
+@example
+AC_ARG_WITH(readline,
+ AS_HELP_STRING([--with-readline],[enable experimental support for readline @@<:@@default=disabled@@:>@@]), ,
+ with_readline=no)
+LIBREADLINE=
+if test "x$with_readline" != xno; then
+ AC_CHECK_LIB(readline, main,
+ [
+ LIBREADLINE="-lreadline -lncurses"
+ AC_DEFINE_UNQUOTED(HAVE_LIBREADLINE, 1, [Define if you have libreadline])
+ ],[
+ AC_MSG_FAILURE([--with-readline was given, but test for readline failed])
+ ], -lncurses)
+fi
+AC_SUBST(LIBREADLINE)
+@end example
+
+The last example shows how to use @code{AC_ARG_WITH} to give the user the
+possibility to disable support for the readline library, given that it is
+an important feature and that it should be enabled by default.
+
+@example
+AC_ARG_WITH(readline,
+ AS_HELP_STRING([--without-readline],[disable support for readline @@<:@@default=enabled@@:>@@]), ,
+ with_readline=yes)
+LIBREADLINE=
+if test "x$with_readline" != xno; then
+ AC_CHECK_LIB(readline, main,
+ [
+ LIBREADLINE="-lreadline -lncurses"
+ AC_DEFINE_UNQUOTED(HAVE_LIBREADLINE, 1, [Define if you have libreadline])
+ ],[
+ AC_MSG_FAILURE([test for readline failed, use --without-readline if you want to force readline support off])
+ ], -lncurses)
+fi
+AC_SUBST(LIBREADLINE)
+@end example
+
+The examples above can be adapted with small effort to the case where
+@code{AC_ARG_ENABLE} should be preferred to @code{AC_ARG_WITH} (see
+@ref{Package Options}).
@end defmac
@defmac AC_WITH (@var{package}, @var{action-if-given}, @ovar{action-if-not-given})
@@ -13292,6 +13364,10 @@
You should format your @var{help-string} with the macro
@code{AS_HELP_STRING} (@pxref{Pretty Help Strings}).
+
+See the examples suggested with the definition of @code{AC_ARG_WITH}
+(@pxref{External Software}) to get an idea of possible utilizations of
+@code{AC_ARG_ENABLE}.
@end defmac
@defmac AC_ENABLE (@var{feature}, @var{action-if-given}, @ovar{action-if-not-given})
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