From 1a956c4b1e8f52b55a2225ace6422c4739f1e43e Mon Sep 17 00:00:00 2001 From: Eric Blake Date: Tue, 14 Jun 2011 07:45:29 -0600 Subject: [PATCH] doc: update quoting example MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit The existing example triggers an autoconf warning, due to the change in AC_COMPILE_IFELSE probing for an AC_LANG_SOURCE use. * doc/autoconf.texi (Autoconf Language): Add AC_LANG_SOURCE use. * THANKS: Update. Reported by Křištof Želechovski. Signed-off-by: Eric Blake --- ChangeLog | 7 +++++++ THANKS | 1 + doc/autoconf.texi | 17 ++++++++++++----- 3 files changed, 20 insertions(+), 5 deletions(-) diff --git a/ChangeLog b/ChangeLog index 1fca7bbf..03541e04 100644 --- a/ChangeLog +++ b/ChangeLog @@ -1,3 +1,10 @@ +2011-06-14 Eric Blake + + doc: update quoting example + * doc/autoconf.texi (Autoconf Language): Add AC_LANG_SOURCE use. + * THANKS: Update. + Reported by Křištof Želechovski. + 2011-05-05 Eric Blake doc: document dash bug with positional parameters diff --git a/THANKS b/THANKS index 7679b054..e125ebe4 100644 --- a/THANKS +++ b/THANKS @@ -235,6 +235,7 @@ Kevin Ryde user42@zip.com.au Klee Dienes kdienes@apple.com Koji Arai JCA02266@nifty.ne.jp Kristian Kvilekval kris@cs.ucsb.edu +Křištof Želechovski giecrilj@stegny.2a.pl Kurt D. Zeilenga kurt@openldap.org Larry Jones larry.jones@sdrc.com Larry Schmitt larry@mail.haleakalawebdesigns.com diff --git a/doc/autoconf.texi b/doc/autoconf.texi index 7ff693f5..99b1fd1f 100644 --- a/doc/autoconf.texi +++ b/doc/autoconf.texi @@ -1288,19 +1288,26 @@ has been continually misunderstood@enddots{} The rule of thumb is that i.e., expect one level of quotes to be lost. For instance: @example -AC_COMPILE_IFELSE([char b[10];], [], [AC_MSG_ERROR([you lose])]) +AC_COMPILE_IFELSE(AC_LANG_SOURCE([char b[10];]), [], + [AC_MSG_ERROR([you lose])]) @end example @noindent -is incorrect: here, the first argument of @code{AC_COMPILE_IFELSE} is +is incorrect: here, the first argument of @code{AC_LANG_SOURCE} is @samp{char b[10];} and is expanded once, which results in -@samp{char b10;}. (There was an idiom common in Autoconf's past to +@samp{char b10;}; and the @code{AC_LANG_SOURCE} is also expanded prior +to being passed to @code{AC_COMPILE_IFELSE}. (There was an idiom common +in Autoconf's past to address this issue via the M4 @code{changequote} primitive, but do not use it!) Let's take a closer look: the author meant the first argument -to be understood as a literal, and therefore it must be quoted twice: +to be understood as a literal, and therefore it must be quoted twice; +likewise, the intermediate @code{AC_LANG_SOURCE} macro should be quoted +once so that it is only expanded after the rest of the body of +@code{AC_COMPILE_IFELSE} is in place: @example -AC_COMPILE_IFELSE([[char b[10];]], [], [AC_MSG_ERROR([you lose])]) +AC_COMPILE_IFELSE([AC_LANG_SOURCE([[char b[10];]])], [], + [AC_MSG_ERROR([you lose])]) @end example @noindent -- 2.47.2