[PATCH, v3] Potential solution to librt issue.

[Paolo Bonzini]

Chris Fairles wrote:
> Uses AC_SEARCH_LIB to check if clock_gettime is in -lrt or -lposix4
> (the latter for some Solaris archs). If its available, "-lrt" is
> assigned to GLIBCXX_LIBS which is AC_SUBST'd so its available in
> Makefile.am's as $(GLIBCXX_LIBS). I've just tacked it onto the LDFLAGS
> for libstdc++.so/a. There might be a more appropriate var to tack it
> onto (ldadd??).

Yes, something like

libstdc___la_LIBADD = $(GLIBCXX_LIBS)
         $(top_builddir)/libmath/libmath.la \
         $(top_builddir)/libsupc++/libsupc++convenience.la \

libstdc___la_DEPENDENCIES = ${version_dep} \
         $(top_builddir)/libmath/libmath.la \
         $(top_builddir)/libsupc++/libsupc++convenience.la

> There's at least one issue: if clock_gettime is a builtin (i.e.
> doesn't require an external lib) then GLIBCXX_LIBS will hold the
> string "none required" which will obviously cause failures during
> linking.

Better to do

AC_SEARCH_LIBS(clock_gettime, [rt posix4])
case "$ac_cv_search_clock_gettime" in
   -l*) GLIBCXX_LIBS=$ac_cv_search_clock_gettime ;;
esac

Ok with those changes.

Paolo