Re: usage of ac_check_header

[Ralf Wildenhues]

Hello Joao,

a small side point regarding M4 quotation: instead of

* Joao Miguel Ferreira wrote on Mon, Jul 23, 2007 at 10:18:08PM CEST:
> AC_CHECK_HEADER(xpath.h,,AC_MSG_ERROR([cannot find headers for libxml2]))

it's better to write this:

AC_CHECK_HEADER(xpath.h,,[AC_MSG_ERROR([cannot find headers for libxml2])])

(quoting the first argument of AC_CHECK_HEADER would be prudent, too).

It was very painful before the last Autoconf release to fix AC_MSG_ERROR
to not rely on this (it cannot because there is loads of old macro code
that has this underquotation, but that doesn't mean we shouldn't advise
against it for new code).

Cheers,
Ralf