[SCM] GNU Autoconf source repository branch, master, updated. v2.69-103-gbefa527

[Eric Blake]

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- Log -----------------------------------------------------------------
commit befa52738c41e126cb9a5a7d4523912ed68b4e3a
Author: Eric Blake <***@redhat.com>
Date: Thu Sep 5 14:14:55 2013 -0600

doc: mention how to set early defaults

Jonathan Lebon reported an issue to me off-list about a regression
in libvirt's configure script, which I traced to a patch that
rearranged code that was checking $with_library compared to the
AC_ARG_WITH that actually set $with_library [1]. As the whole point
of the libvirt patch was to refactor code to make maintenance
easier by hiding the AC_ARG_WITH in a helper macro for a net
reduction in lines, it makes sense to actually document how to
check what value a variable has prior to the AC_ARG_WITH usage.

Alas, although the functionality for this has been present in
autoconf for ages, the documentation has been lacking.

[1] libvirt.org/git/?p=libvirt.git;a=commitdiff;h=654c709

* doc/autoconf.texi (Diversion support) <m4_divert_text>: Add
anchor.
(External Software) <AC_ARG_WITH>: Demonstrate how to use DEFAULTS
diversion, for earlier defaults.
(Package Options) <AC_ARG_ENABLE>: Likewise.
* THANKS: Add Jonathan Lebon.

Signed-off-by: Eric Blake <***@redhat.com>

-----------------------------------------------------------------------

Summary of changes:
THANKS | 1 +
doc/autoconf.texi | 19 ++++++++++++++++++-
2 files changed, 19 insertions(+), 1 deletions(-)

diff --git a/THANKS b/THANKS
index 1e3e5ef..f41f16c 100644
--- a/THANKS
+++ b/THANKS
@@ -210,6 +210,7 @@ John Interrante ***@uluru.stanford.edu
John R. Cary ***@txcorp.com
John W. Eaton ***@bevo.che.wisc.edu
Jonathan Kamens ***@kamens.brookline.ma.us
+Jonathan Lebon ***@redhat.com
Josef Tran ***@timetrackertechnology.com
Josef Vukovic ***@googlemail.com
Joseph S. Myers ***@cam.ac.uk
diff --git a/doc/autoconf.texi b/doc/autoconf.texi
index 3c559a5..26e7b17 100644
--- a/doc/autoconf.texi
+++ b/doc/autoconf.texi
@@ -11997,6 +11997,7 @@ stack, and issues an error if there is not a matching pop for every
push.
@end defmac

+@anchor{m4_divert_text}
@defmac m4_divert_text (@var{diversion}, @ovar{content})
@msindex{divert_text}
Output @var{content} and a newline into @var{diversion}, without
@@ -22085,6 +22086,14 @@ actually just the value of the shell variable named
@var{package} changed into @samp{_}. You may use that variable instead,
if you wish.

+Note that @var{action-if-not-given} is not expanded until the point that
+@code{AC_ARG_WITH} was expanded. If you need the value of
+@code{***@var{package}} set to a default value by the time argument
+parsing is completed, use @code{m4_divert_text} to the @code{DEFAULTS}
+diversion (@pxref{m4_divert_text}) (if done as an argument to
+@code{AC_ARG_WITH}, also provide non-diverted text to avoid a shell
+syntax error).
+
The argument @var{help-string} is a description of the option that
looks like this:
@example
@@ -22111,7 +22120,7 @@ AC_ARG_WITH([readline],
[AS_HELP_STRING([--with-readline],
[support fancy command line editing @@<:@@default=check@@:>@@])],
[],
- [with_readline=check])
+ [: m4_divert_text([DEFAULTS], [with_readline=check])])

LIBREADLINE=
AS_IF([test "x$with_readline" != xno],
@@ -22238,6 +22247,14 @@ actually just the value of the shell variable named
if you wish. The @var{help-string} argument is like that of
@code{AC_ARG_WITH} (@pxref{External Software}).

+Note that @var{action-if-not-given} is not expanded until the point that
+@code{AC_ARG_ENABLE} was expanded. If you need the value of
+@code{***@var{feature}} set to a default value by the time argument
+parsing is completed, use @code{m4_divert_text} to the @code{DEFAULTS}
+diversion (@pxref{m4_divert_text}) (if done as an argument to
+@code{AC_ARG_ENABLE}, also provide non-diverted text to avoid a shell
+syntax error).
+
You should format your @var{help-string} with the macro
@code{AS_HELP_STRING} (@pxref{Pretty Help Strings}).



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