[Spice-devel] [PATCH spice-common v2 1/2] spice-deps: Make LZ4 check depending on function

[Pavel Grunt]

On Thu, 2016-11-24 at 09:33 -0500, Frediano Ziglio wrote:
> > 
> > LZ4 changed versioning scheme from r131 to v1.7.3 making our
> > configure
> > fail with (1.7.3 < 129).
> > 
> > Switch from version checking to checking that the necessary
> > function
> > is available.
> > ---
> > v2: Added some comments, Switched to AC_CHECK_FUNC
> > ---
> >  m4/spice-deps.m4 | 22 ++++++++++++++++++----
> >  1 file changed, 18 insertions(+), 4 deletions(-)
> > 
> > diff --git a/m4/spice-deps.m4 b/m4/spice-deps.m4
> > index adedec4..6827c7f 100644
> > --- a/m4/spice-deps.m4
> > +++ b/m4/spice-deps.m4
> > @@ -185,12 +185,26 @@ AC_DEFUN([SPICE_CHECK_LZ4], [
> >  
> >      have_lz4="no"
> >      if test "x$enable_lz4" != "xno"; then
> > -      PKG_CHECK_MODULES([LZ4], [liblz4 >= 129], [have_lz4="yes"],
> > [have_lz4="no"])
> > +      # LZ4_compress_default is available in liblz4 >= 129,
> > however liblz
> > has changed
> > +      # versioning scheme making the check failing. Rather check
> > for
> > function definition
> > +      PKG_CHECK_MODULES([LZ4], [liblz4], [have_lz4="yes"],
> > [have_lz4="no"])
> >  
> >        if test "x$have_lz4" = "xyes"; then
> > -        AC_DEFINE(USE_LZ4, [1], [Define to build with lz4
> > support])
> > -      elif test "x$enable_lz4" = "xyes"; then
> > -        AC_MSG_ERROR([lz4 support requested but liblz4 could not
> > be found])
> > +        # For cross-compilers may be necessary to save & restore
> > LIBS and
> > CFLAGS before AC_SEARCH_LIBS
> > +        old_LIBS="$LIBS"
> > +        old_CFLAGS="$CFLAGS"
> > +        CFLAGS="$CFLAGS $LZ4_CFLAGS"
> > +        LIBS="$LIBS $LZ4_LIBS"
> > +
> > +        AC_CHECK_FUNC([LZ4_compress_default], [
> > +            AC_DEFINE(USE_LZ4, [1], [Define to build with lz4
> > support])],
> > +            [have_lz4="no"])
> > +
> > +        LIBS="$old_LIBS"
> > +        CFLAGS="$old_CFLAGS"
> > +      fi
> > +      if test "x$enable_lz4" = "xyes" && test "x$have_lz4" =
> > "xno"; then
> 
> I think this xyes/xno it's kind of a fix for shell bug quite long
> ago, a
> 
>    if test "$enable_lz4" = yes -a "$have_lz4" = no; then
> 
> will work. Even [ is more readable leading to
> 
>    if [ "$enable_lz4" = yes -a "$have_lz4" = no ]; then
> 
> configure try to use very old style to make sure compatibility is
> good
> but this lead to really ugly syntax sometimes.

it is a style used in all our configure.ac and m4 files. It may be
ugly/not easy to follow but I don't think it is worth spending time on
improving it everywhere... 


> 
> > +        AC_MSG_ERROR([lz4 support requested but liblz4 >= 129
> > could not be
> > found])
> >        fi
> >      fi
> >      AM_CONDITIONAL(HAVE_LZ4, test "x$have_lz4" = "xyes")
> 
> Frediano