On 09/10/2012 06:14 PM, Eric Blake wrote:
Recent spec file changes ensure that in distro situations, netcf and libvirt will link against the same libnl in order to avoid dumping core. But for every-day development, if you are F17 and have the libnl3-devel headers available, libvirt was blindly linking against libnl3 even though F17 netcf still links against libnl1, making testing a self-built binary on F17 impossible.
By making configure a little bit smarter, we can avoid this situation - we merely skip the probe of libnl-3 if we can prove that netcf is still using libnl-1. I intentionally wrote the test so that we still favor libnl-3 if netcf is not installed or if we couldn't use ldd to determine things.
Defaults being what they are, someone will invariably complain that our smarts were wrong. Never fear - in that case, just run ./configure LIBNL_CFLAGS=..., where the fact that you set LIBNL_CFLAGS (even to the empty string) will go back to probing for libnl-3, regardless of netcf's choice.
This method of forcing libnl-3 is a bit obscure, but it will be used infrequently enough (possibly never? :-P) that I'm okay doing it that way, as long as you add a comment to configure.ac briefly explaining it (as you've done in the commit message). ACK with that added.
* configure.ac (LIBNL): Don't probe libnl3 if netcf doesn't use it. ---
v2: check for libnetcf.so, in usual suspect locations; and document a way to override things if the guess is wrong.
configure.ac | 34 +++++++++++++++++++++++++--------- 1 file changed, 25 insertions(+), 9 deletions(-)
diff --git a/configure.ac b/configure.ac index 47a72b9..6a96bf3 100644 --- a/configure.ac +++ b/configure.ac @@ -2902,14 +2902,30 @@ LIBNL_LIBS="" have_libnl=no
if test "$with_linux" = "yes"; then - PKG_CHECK_MODULES([LIBNL], [libnl-3.0], [ - have_libnl=yes - AC_DEFINE([HAVE_LIBNL3], [1], [Use libnl-3.0]) - AC_DEFINE([HAVE_LIBNL], [1], [whether the netlink library is available]) - PKG_CHECK_MODULES([LIBNL_ROUTE3], [libnl-route-3.0]) - LIBNL_CFLAGS="$LIBNL_CFLAGS $LIBNL_ROUTE3_CFLAGS" - LIBNL_LIBS="$LIBNL_LIBS $LIBNL_ROUTE3_LIBS" - ], [PKG_CHECK_MODULES([LIBNL], [libnl-1 >= $LIBNL_REQUIRED], [ + # When linking with netcf, we must ensure that we pick the same version + # of libnl that netcf picked. Prefer libnl-3 unless we can prove + # netcf linked against libnl-1, or unless the user set LIBNL_CFLAGS. + libnl_ldd= + for dir in /usr/lib64 /usr/lib; do + if test -f $dir/libnetcf.so; then + libnl_ldd=`(ldd $dir/libnetcf.so) 2>&1` + break + fi + done + case $libnl_ldd:${LIBNL_CFLAGS+set} in + *libnl.so.1*:) ;; + *) + PKG_CHECK_MODULES([LIBNL], [libnl-3.0], [ + have_libnl=yes + AC_DEFINE([HAVE_LIBNL3], [1], [Use libnl-3.0]) + AC_DEFINE([HAVE_LIBNL], [1], [whether the netlink library is available]) + PKG_CHECK_MODULES([LIBNL_ROUTE3], [libnl-route-3.0]) + LIBNL_CFLAGS="$LIBNL_CFLAGS $LIBNL_ROUTE3_CFLAGS" + LIBNL_LIBS="$LIBNL_LIBS $LIBNL_ROUTE3_LIBS" + ], []) ;; + esac + if test "$have_libnl" = no; then + PKG_CHECK_MODULES([LIBNL], [libnl-1 >= $LIBNL_REQUIRED], [ have_libnl=yes AC_DEFINE_UNQUOTED([HAVE_LIBNL], [1], [whether the netlink library is available]) @@ -2920,7 +2936,7 @@ if test "$with_linux" = "yes"; then AC_MSG_ERROR([libnl-devel >= $LIBNL_REQUIRED is required for macvtap support]) fi ]) - ]) + fi fi AM_CONDITIONAL([HAVE_LIBNL], [test "$have_libnl" = "yes"])