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doc: update quoting example

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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 <eblake@redhat.com>
This commit is contained in:
Eric Blake 2011-06-14 07:45:29 -06:00
parent 2105ae9700
commit 1a956c4b1e
3 changed files with 20 additions and 5 deletions
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7
ChangeLog
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@ -1,3 +1,10 @@
2011-06-14 Eric Blake <eblake@redhat.com>
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 <eblake@redhat.com>
doc: document dash bug with positional parameters

1
THANKS
View File

@ -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

17
doc/autoconf.texi
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@ -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