File: autoconf.info,  Node: Changed Quotation,  Next: New Macros,  Up: Autoconf 2.13

18.6.1 Changed Quotation
------------------------

The most important changes are invisible to you: the implementation of
most macros have completely changed.  This allowed more factorization of
the code, better error messages, a higher uniformity of the user's
interface etc.  Unfortunately, as a side effect, some construct which
used to (miraculously) work might break starting with Autoconf 2.50.
The most common culprit is bad quotation.

   For instance, in the following example, the message is not properly
quoted:

     AC_INIT
     AC_CHECK_HEADERS(foo.h, ,
       AC_MSG_ERROR(cannot find foo.h, bailing out))
     AC_OUTPUT

Autoconf 2.13 simply ignores it:

     $ autoconf-2.13; ./configure --silent
     creating cache ./config.cache
     configure: error: cannot find foo.h
     $

while Autoconf 2.50 produces a broken ‘configure’:

     $ autoconf-2.50; ./configure --silent
     configure: error: cannot find foo.h
     ./configure: exit: bad non-numeric arg `bailing'
     ./configure: exit: bad non-numeric arg `bailing'
     $

   The message needs to be quoted, and the ‘AC_MSG_ERROR’ invocation
too!

     AC_INIT([Example], [1.0], [bug-example@example.org])
     AC_CHECK_HEADERS([foo.h], [],
       [AC_MSG_ERROR([cannot find foo.h, bailing out])])
     AC_OUTPUT

   Many many (and many more) Autoconf macros were lacking proper
quotation, including no less than... ‘AC_DEFUN’ itself!

     $ cat configure.in
     AC_DEFUN([AC_PROG_INSTALL],
     [# My own much better version
     ])
     AC_INIT
     AC_PROG_INSTALL
     AC_OUTPUT
     $ autoconf-2.13
     autoconf: Undefined macros:
     ***BUG in Autoconf--please report*** AC_FD_MSG
     ***BUG in Autoconf--please report*** AC_EPI
     configure.in:1:AC_DEFUN([AC_PROG_INSTALL],
     configure.in:5:AC_PROG_INSTALL
     $ autoconf-2.50
     $