Re: usage of ac_check_header

[Keith Marshall]

On Tuesday 24 July 2007 10:44, Joao Miguel Ferreira wrote:
> >   AC_CHECK_HEADER([libxml2/libxml/xpath.h],,
> >     [AC_MSG_ERROR([cannot find xml headers])])
>
> Well... I'm unable to get my system to work as yours... it seems to
> me your system is not refusing to look into
> /usr/include/libxml2/..... mine is...

Nope.  I *told* AC_CHECK_HEADER to look in <default-path>/libxml2; you 
did not.

> In order to get this to work I had to explicitlly 'ask' ./configure
> dig into the libxml2 dir.... check this out (configure.ac)
>
> ----------------------------------------------
> XTRAINCPATHS="-I/usr/include/libxml2/"
> CFLAGS="$CFLAGS $XTRAINCPATHS"
> CPPFLAGS="$CPPFLAGS $XTRAINCPATHS"
> #now that we got the include paths right lets check
>
> AC_CHECK_HEADERS([libxml/xmlreader.h
> libxml/xpath.h],,AC_MSG_ERROR([cannot find headers for libxml2]))

Notice that your example would be equivalent, in respect of the search 
path determination, to...

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

...whereas I explicitly made it relative to *any* default include path 
searched by the compiler...

  AC_CHECK_HEADER([libxml2/libxml/xpath.h],,
    [AC_MSG_ERROR([cannot find xml headers])])

In my case, that default search path is /usr/include; if the same 
doesn't work for you, then the only conclusion that can be drawn is 
that /usr/include is not a default include path, in your compiler 
configuration.

Regards,
Keith.