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Re: AC_DEFINE defaulting to 1
From: |
Paul Eggert |
Subject: |
Re: AC_DEFINE defaulting to 1 |
Date: |
Wed, 11 Sep 2002 12:06:36 -0700 (PDT) |
> From: Akim Demaille <address@hidden>
> Date: 11 Sep 2002 17:23:02 +0200
>
> I think the doc should be fixed: I see no reason to prevent someone
> from just defining to nothing :(
I too have been confused by this in the past, so I installed the
following doc patch.
2002-09-11 Paul Eggert <address@hidden>
* doc/autoconf.texi (Defining Symbols): Explain that
AC_DEFINE(var) defaults to 1, but AC_DEFINE(var,,description) does
not; and the AC_DEFINE(var) case is obsolescent.
Index: autoconf.texi
===================================================================
RCS file: /cvsroot/autoconf/autoconf/doc/autoconf.texi,v
retrieving revision 1.671
retrieving revision 1.672
diff -p -u -r1.671 -r1.672
--- autoconf.texi 11 Sep 2002 10:11:27 -0000 1.671
+++ autoconf.texi 11 Sep 2002 19:03:59 -0000 1.672
@@ -6087,8 +6087,7 @@ output.
@defmac AC_DEFINE (@var{variable}, @ovar{value}, @ovar{description})
@acindex DEFINE
-Define C preprocessor variable @var{variable}. If @var{value} is given,
-set @var{variable} to that value (verbatim), otherwise set it to 1.
+Define the C preprocessor variable @var{variable} to @var{value} (verbatim).
@var{value} should not contain literal newlines, and if you are not
using @code{AC_CONFIG_HEADERS} it should not contain any @samp{#}
characters, as @command{make} tends to eat them. To use a shell variable
@@ -6103,6 +6102,12 @@ The following example defines the C prep
@example
AC_DEFINE(EQUATION, "$a > $b")
@end example
+
+If neither @var{value} nor @var{description} are given, then
address@hidden defaults to 1 instead of to the empty string. This is for
+backwards compatiblity with older versions of Autoconf, but this usage
+is obsolescent and may be withdrawn in future versions of Autoconf.
+
@end defmac
@defmac AC_DEFINE_UNQUOTED (@var{variable}, @ovar{value}, @ovar{description})
- Re: AC_DEFINE defaulting to 1,
Paul Eggert <=