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libvirt/m4/virt-linker-no-undefined.m4
Daniel P. Berrangé a1f6030def build: passing the "-z defs" linker flag to prevent undefined symbols
Undefined symbols are a bad thing in general because they can get
resolved in unexpected ways at runtime if multiple sources provide the
same symbol name. For example both glibc and libtirpc may provide XDR
symbols and we want to ensure that we resolve to libtirpc if that's what
we originally built against.

The toolchain maintainers thus strongly recommend that all applications
use the '-z defs' linker flag to prevent undefined symbols. This is
shortly becoming part of the default linker flags for RPMs. As an added
benefit this aligns Linux builds with Windows builds, where the linker
has never permitted undefined symbols.

Signed-off-by: Daniel P. Berrange <berrange@redhat.com>
2018-02-09 11:05:10 +00:00

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dnl
dnl Check for -z defs linker flag
dnl
dnl Copyright (C) 2013-2018 Red Hat, Inc.
dnl
dnl This library is free software; you can redistribute it and/or
dnl modify it under the terms of the GNU Lesser General Public
dnl License as published by the Free Software Foundation; either
dnl version 2.1 of the License, or (at your option) any later version.
dnl
dnl This library is distributed in the hope that it will be useful,
dnl but WITHOUT ANY WARRANTY; without even the implied warranty of
dnl MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
dnl Lesser General Public License for more details.
dnl
dnl You should have received a copy of the GNU Lesser General Public
dnl License along with this library. If not, see
dnl <http://www.gnu.org/licenses/>.
dnl
AC_DEFUN([LIBVIRT_LINKER_NO_UNDEFINED],[
AC_MSG_CHECKING([for how to stop undefined symbols at link time])
NO_UNDEFINED_LDFLAGS=
ld_help=`$LD --help 2>&1`
case $ld_help in
*"-z defs"*) NO_UNDEFINED_LDFLAGS="-Wl,-z -Wl,defs" ;;
esac
AC_SUBST([NO_UNDEFINED_LDFLAGS])
AC_MSG_RESULT([$NO_UNDEFINED_LDFLAGS])
])