[Buildroot] autotools, pkg_config and mysql_config

[Kinsella, Ray]

That does help, thanks Thomas.

Ray K

On Fri, 2016-03-25 at 16:38 +0100, Thomas Petazzoni wrote:
> Hello,
> 
> On Thu, 24 Mar 2016 20:25:02 +0000, Kinsella, Ray wrote:
> 
> > SQLite - worked like a dream, with two lines in my configure.ac
> > 
> > PKG_CHECK_MODULES([SQLITE3], [sqlite3], [have_libsqlite3=yes],
> > [have_libsqlite3=no])$
> > AM_CONDITIONAL([LIB_SQLITE3],  [test "$have_libsqlite3" = "yes"])$
> 
> This automake variable should rather be called HAVE_SQLITE3, and not
> LIB_SQLITE3.
> 
> > However mysql, in an effort to be slightly different - doesn't use
> > pkg_config, so you therefore can't use PKG_CHECK_MODULES. Instead
> > it ships its own tool mysql_config.
> > 
> > So I wrote some autoconf, to handle that ...
> > 
> > AX_WITH_PROG([MYSQL_CONFIG], [mysql_config],
> > [AC_MSG_ERROR(mysql_config is required to build)])$
> 
> Why do you use AX_WITH_PROG instead of AC_PATH_PROG ?
> 
> > if test "x$MYSQL_CONFIG" != "x";then$
> >   AC_CHECK_HEADERS([mysql.h mysql/mysql.h])$
> 
> It doesn't seem to make sense to check for MySQL headers before
> fetching the MySQL CFLAGS. Indeed, how can you expect to check the
> MySQL headers if you haven't yet asked mysql_config for the headers?
> 
> I would simply drop this check in fact, and simply rely on whether
> mysql_config exists or not.
> 
> >   if test "x$ac_cv_header_mysql_h" != "xno" -o
> > "x$ac_cv_header_mysql_mysql_h" != "xno" ; then$
> >     MYSQL_CFLAGS=`$MYSQL_CONFIG --cflags`$
> >     MYSQL_LIBS=`$MYSQL_CONFIG --libs`$
> >     AC_SUBST([MYSQL_CFLAGS])$
> >     AC_SUBST([MYSQL_LIBS])$
> >   fi$
> > fi$
> 
> I am not sure why you have a $ at the end of each line.
> 
> > AM_CONDITIONAL([LIB_MYSQL],  [test "x$mysql_config" != "x"])
> 
> Ditto, I would call the variable HAVE_MYSQL.
> 
> > My problem is that, it is continually picking myconfig from my host
> > system. So end up with $MYSQL_CONFIG=/usr/bin/mysql_config instead
> > of target/usr/bin/mysql_config. MYSQL_CFLAGS and MYSQL_LIBS
> > therefore also end up pointing at the host.
> 
> Buildroot will install mysql_config in $(STAGING_DIR)/usr/bin, which
> is
> not in the PATH. So you have to explicitly tell your configure script
> where it is located. If you use AC_PATH_PROG, you simply need to
> pass:
> 
> 	ac_cv_path_MYSQL_CONFIG=$(STAGING_DIR)/usr/bin/mysql_config
> 
> in RADLIB_CONF_ENV.
> 
> Some examples from Buildroot:
> 
> package/directfb/directfb.mk:DIRECTFB_CONF_ENV +=
> ac_cv_path_LIBPNG_CONFIG=$(STAGING_DIR)/usr/bin/libpng-config
> package/directfb/directfb.mk:DIRECTFB_CONF_ENV +=
> ac_cv_path_IMLIB2_CONFIG=$(STAGING_DIR)/usr/bin/imlib2-config
> package/gnupg/gnupg.mk:GNUPG_CONF_ENV +=
> ac_cv_path__libcurl_config=$(STAGING_DIR)/usr/bin/curl-config
> package/gnuplot/gnuplot.mk:    
>  ac_cv_path_GDLIB_CONFIG=$(STAGING_DIR)/usr/bin/gdlib-config
> etc, etc.
> 
> And there's even one example with MySQL:
> 
> package/kodi/kodi.mk:KODI_CONF_ENV +=
> ac_cv_path_MYSQL_CONFIG="$(STAGING_DIR)/usr/bin/mysql_config"
> 
> Hope this helps,
> 
> Thomas