Re: [Qemu-devel] [PATCH] configure: Support pkg-config for zlib

["Daniel P. Berrangé" <berrange@redhat.com>]

On Wed, Jul 18, 2018 at 06:59:25PM +0200, Stefan Weil wrote:
> Am 18.07.2018 um 18:21 schrieb Daniel P. Berrangé:
> > On Thu, Jul 12, 2018 at 09:26:03PM +0200, Stefan Weil wrote:
> >> This is needed for builds with the mingw64-* packages from Cygwin,
> >> but also works for Linux.
> >>
> >> Move the zlib test also more to the end because users should
> >> get information on the really important missing packages
> >> (which also require zlib) first.
> > 
> > According to the zlib Changelog file pkgconfig support was added
> > in 2006 !
> > 
> > [quote]
> > Changes in 1.2.3.1 (16 August 2006)
> > 
> >   - Add pkgconfig support [Weigelt]
> > [/quote]
> > 
> > Given our target build platforms support guidelines
> > 
> >   https://qemu.weilnetz.de/doc/qemu-doc.html#Supported-build-platforms
> > 
> > we can safely say that all supported platforms will have a zlib
> > that contains pkgconfig support, so......
> > 
> >>
> >> Signed-off-by: Stefan Weil <sw@weilnetz.de>
> >> ---
> >>  configure | 40 +++++++++++++++++++++++-----------------
> >>  1 file changed, 23 insertions(+), 17 deletions(-)
> >>
> >> diff --git a/configure b/configure
> >> index 2a7796ea80..dcaab01729 100755
> >> --- a/configure
> >> +++ b/configure
> >> @@ -2140,23 +2140,6 @@ EOF
> >>    fi
> >>  fi
> >>  
> >> -#########################################
> >> -# zlib check
> >> -
> >> -if test "$zlib" != "no" ; then
> >> -    cat > $TMPC << EOF
> >> -#include <zlib.h>
> >> -int main(void) { zlibVersion(); return 0; }
> >> -EOF
> >> -    if compile_prog "" "-lz" ; then
> >> -        :
> >> -    else
> >> -        error_exit "zlib check failed" \
> >> -            "Make sure to have the zlib libs and headers installed."
> >> -    fi
> >> -fi
> >> -LIBS="$LIBS -lz"
> >> -
> >>  ##########################################
> >>  # lzo check
> >>  
> >> @@ -3525,6 +3508,29 @@ if ! compile_prog "$glib_cflags -Werror" "$glib_libs" ; then
> >>      fi
> >>  fi
> >>  
> >> +#########################################
> >> +# zlib check
> >> +
> >> +if test "$zlib" != "no" ; then
> >> +    if $pkg_config --exists zlib; then
> >> +        zlib_cflags=$($pkg_config --cflags zlib)
> >> +        zlib_libs=$($pkg_config --libs zlib)
> >> +        QEMU_CFLAGS="$zlib_cflags $QEMU_CFLAGS"
> >> +        LIBS="$zlib_libs $LIBS"
> >> +    else
> >> +        cat > $TMPC << EOF
> >> +#include <zlib.h>
> >> +int main(void) { zlibVersion(); return 0; }
> >> +EOF
> >> +        if compile_prog "" "-lz" ; then
> >> +            LIBS="$LIBS -lz"
> >> +        else
> >> +            error_exit "zlib check failed" \
> >> +                "Make sure to have the zlib libs and headers installed."
> >> +        fi
> >> +    fi
> > 
> > .... this fallback support for non-pkgconfig scenarios can be entirely
> > deleted, just leaving the error_exit message. 
> 
> I have no objection. Thank you for the investigation of the zlib
> history. Removing old unneeded code is always good, but maybe that's
> something which could be done after release 3.0.
> 
> Or would you suggest to do it now? Then I can either send an updated
> patch (v2), or whoever pulls that patch can make that trivial modification.

If we're ok with adding support for pkg-config in 3.0, I think it is
reasonable to drop the fallback check at the same time.  I think it
this stills qualify as a bug fix patch in terms of our freeze rules,
since we're specificially aiming to fix build problems on one of our
supported platforms.

So personally I'd suggest sending a v2 with the fallback dropped.
for 3.0

Regards,
Daniel
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