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According to santilistas on 8/9/2009 11:08 AM:
[finally getting to this thread]
> By the way, is this the correct list to send this remarks?
>
> In section 3.1.2 The Autoconf language, there is the example on Iron
> Maiden and AC_DC.
>
> @example
> echo "Hard rock was here! --[AC_DC]"
> @end example
in configure.ac
>
> which results in:
>
> @example
> echo "Hard rock was here! --AC_DC"
> @end example
in configure
> that demonstrates the losing of the quotation. However, a little bit
> below there is this example:
>
> @example
> AC_MSG_WARN([[AC_DC stinks --Iron Maiden]])
> @end example
in configure.ac
which leads to something roughly like:
$as_echo "AC_DC stinks --Iron Maiden"
in configure.
>
> which tries to show that the quotation is lost, but there is no quotation.
There WAS quotation - the double quotes were around the entire sentence,
rather than just the problematic section. But I can improve the example
to mention which file we are looking at, and show both quoting styles:
> @example
> [echo "Hard rock was here! --AC_DC"] dnl style 1
> echo "Hard rock was here! --[AC_DC]" dnl style 2
> @end example
in configure.ac, leads to:
> @example
> echo "Hard rock was here! --AC_DC"
> echo "Hard rock was here! --AC_DC"
> @end example
in configure.
>
> Shouldn't it be written like this?:
>
> @example
> AC_MSG_WARN([[AC_DC stinks --[Iron Maiden] ]])
> @end example
No, unless we want [] in configure, which is NOT what the first example
was doing.
> --santilín
Do you have a full name that you'd like to be credited as in the THANKS
file? Other than that, here's what I'm thinking of pushing.
- --
Don't work too hard, make some time for fun as well!
Eric Blake ebb9@xxxxxxx
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>From 881638c743d349a62ab32664d6d27e7bd26f4d9e Mon Sep 17 00:00:00 2001
From: Eric Blake <ebb9@xxxxxxx>
Date: Thu, 10 Sep 2009 20:47:50 -0600
Subject: [PATCH] Improve documentation on quoting.
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit
* doc/autoconf.texi (Autoconf Language): Clarify quoting example.
* THANKS: Update.
Reported by santilÃn.
Signed-off-by: Eric Blake <ebb9@xxxxxxx>
---
ChangeLog | 5 +++++
doc/autoconf.texi | 23 ++++++++++++++++++++---
2 files changed, 25 insertions(+), 3 deletions(-)
diff --git a/ChangeLog b/ChangeLog
index 9ea4ed6..97bed79 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,10 @@
2009-09-10 Eric Blake <ebb9@xxxxxxx>
+ Improve documentation on quoting.
+ * doc/autoconf.texi (Autoconf Language): Clarify quoting example.
+ * THANKS: Update.
+ Reported by santilÃn.
+
Document that AS_INIT is automatically used.
* doc/autoconf.texi (Initialization Macros) <AS_INIT>: Add words
to clarify that only bare-bones scripts need a direct AS_INIT.
diff --git a/doc/autoconf.texi b/doc/autoconf.texi
index 4203cd0..50583f5 100644
--- a/doc/autoconf.texi
+++ b/doc/autoconf.texi
@@ -1177,29 +1177,46 @@ Autoconf Language
In other cases, you may have to use text that also resembles a macro
call. You must quote that text even when it is not passed as a macro
-argument:
+argument. For example, these two approaches in @file{configure.ac}
+(quoting just the potential problems, or quoting the entire line) will
+protect your script in case autoconf ever adds a macro @code{AC_DC}:
@example
echo "Hard rock was here! --[AC_DC]"
+[echo "Hard rock was here! --AC_DC"]
@end example
@noindent
-which results in:
+which results in this text in @file{configure}:
@example
echo "Hard rock was here! --AC_DC"
+echo "Hard rock was here! --AC_DC"
@end example
@noindent
When you use the same text in a macro argument, you must therefore have
an extra quotation level (since one is stripped away by the macro
substitution). In general, then, it is a good idea to @emph{use double
-quoting for all literal string arguments}:
+quoting for all literal string arguments}, either around just the
+problematic portions, or over the entire argument:
@example
+AC_MSG_WARN([[AC_DC] stinks --Iron Maiden])
AC_MSG_WARN([[AC_DC stinks --Iron Maiden]])
@end example
+However, the above example triggers a warning about a possibly
+unexpanded macro when running @command{autoconf}, because it collides
+with the namespace of macros reserved for the Autoconf language. To be
+really safe, you can use additional escaping (either a quadrigraph, or
+creative shell constructs) to silence that particular warning:
+
+@example
+echo "Hard rock was here! --AC""_DC"
+AC_MSG_WARN([[AC@@&t@@_DC stinks --Iron Maiden]])
+@end example
+
You are now able to understand one of the constructs of Autoconf that
has been continually misunderstood@enddots{} The rule of thumb is that
@emph{whenever you expect macro expansion, expect quote expansion};
--
1.6.3.3.334.g916e1
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