[PATCH weston] configure.ac: make use of wayland-scanner.pc

[Pekka Paalanen]

On Sat, 21 Feb 2015 12:10:43 -0800
Bryce Harrington <bryce at osg.samsung.com> wrote:

> On Sat, Feb 21, 2015 at 11:04:13AM +0000, Emil Velikov wrote:
> > Hi Bryce
> > 
> > On 20 February 2015 at 23:26, Bryce Harrington <bryce at osg.samsung.com> wrote:
> > > On Tue, Feb 17, 2015 at 03:13:32PM +0000, Emil Velikov wrote:
> > >> Currently we use the wayland-scanner executable as found with
> > >> AC_PATH_PROG, and then check the presence of wayland-scanner.pc
> > >>
> > >> Currently the latter is unused even if AC_PATH_PROG fails to find the
> > >> binary. Rework things to use the pkg-config variable as a fall-back.
> > >
> > > Sorry to have to ask some rather stupid questions, but I want to make
> > > sure I understand the effects of this before landing.
> > >
> > >> Cc: Andrew Oakley <aoakley at espial.com>
> > >> Cc: Bill Spitzak <spitzak at gmail.com>
> > >> Cc: Daniel Stone <daniel at fooishbar.org>
> > >> Signed-off-by: Emil Velikov <emil.l.velikov at gmail.com>
> > >> ---
> > >>  configure.ac | 5 ++---
> > >>  1 file changed, 2 insertions(+), 3 deletions(-)
> > >>
> > >> diff --git a/configure.ac b/configure.ac
> > >> index 1db9f79..b44675f 100644
> > >> --- a/configure.ac
> > >> +++ b/configure.ac
> > >> @@ -503,11 +503,10 @@ AM_CONDITIONAL(HAVE_LCMS, [test "x$have_lcms" = xyes])
> > >>
> > >>  AC_PATH_PROG([wayland_scanner], [wayland-scanner])
> > >>  if test x$wayland_scanner = x; then
> > >> -     AC_MSG_ERROR([wayland-scanner is needed to compile weston])
> > >
> > > Shouldn't there still be an error message generated if the $PKG_CONFIG
> > > run (below) fails?
> > >
> > The macro has an optional [action-if-not-found]. If it's missing (as
> > below) we will error out by default.
> > 
> > >> +     PKG_CHECK_MODULES(WAYLAND_SCANNER, [wayland-scanner])
> > >
> > > Here's where I think I'm confused.  The main purpose of
> > > PKG_CHECK_MODULES as I understand it is to define CFLAGS and LIBS
> > > variables, so this would be e.g. WAYLAND_SCANNER_CFLAGS and
> > > WAYLAND_SCANNER_LIBS.  Yet I'm not spotting where either of these are
> > > actually used.  We only need the binary, not the library stuff, right?
> > > Is it declaring any other variables or doing other work we need?
> > >
> > Afaik the macro does three things
> >  1 Check for the presence of the required package(s)
> >  2 Sets the relevant _CFLAGS and _LIBS variables.
> >  3 Errors out with a very informative message, when
> > action-if-not-found is not set.
> > 
> > Here we're using it for 1 & 3. One can use PKG_CHECK_EXISTS() and then
> > manually add the error message, but that is rather uncommon afaict.
> > 
> > Hope that clears things up a bit.
> 
> Thank you, yes that does.
> 
> I'll give Bill and Daniels a chance to comment, but meanwhile:
> 
> Reviewed-by: Bryce Harrington <bryce at osg.samsung.com>

Hi,

yeah, this looks good to me, particularly after Andrew Oakley first
pointed out the cross-compilation case, and then accepted this revision.
Cross-compilation would've been my major concern.


Thanks,
pq