Depending on the platform/architecture, a number of conditionals in libvirt code expand the same on both branches. This is expected behaviour and harmless, so disable the warning to avoid creating unexpected build failures Two examples, mingw32: ../../src/util/vircommand.c: In function 'virCommandWait': ../../src/util/vircommand.c:2562:51: error: this condition has identical branches [-Werror=duplicated-branches] *exitstatus = cmd->rawStatus ? status : WEXITSTATUS(status); ^ and gcc7.1 In file included from util/virobject.c:28:0: util/virobject.c: In function 'virClassNew': util/viratomic.h:176:46: error: this condition has identical branches [-Werror=duplicated-branches] (void)(0 ? *(atomic) ^ *(atomic) : 0); \ ^ util/virobject.c:144:20: note: in expansion of macro 'virAtomicIntInc' klass->magic = virAtomicIntInc(&magicCounter); ^~~~~~~~~~~~~~~ Signed-off-by: Daniel P. Berrange <berrange(a)redhat.com&gt; --- m4/virt-compile-warnings.m4 | 3 +++ 1 file changed, 3 insertions(+) diff --git a/m4/virt-compile-warnings.m4 b/m4/virt-compile-warnings.m4 index 768a5c8..d7bb172 100644 --- a/m4/virt-compile-warnings.m4 +++ b/m4/virt-compile-warnings.m4 @@ -61,6 +61,9 @@ AC_DEFUN([LIBVIRT_COMPILE_WARNINGS],[ dontwarn="$dontwarn -Wenum-compare" # gcc 5.1 -Wformat-signedness mishandles enums, not ready for prime time dontwarn="$dontwarn -Wformat-signedness" + # Several conditionals expand the same on both branches + # depending on the particular platform/architecture + dontwarn="$dontwarn -Wduplicated-branches" # gcc 4.2 treats attribute(format) as an implicit attribute(nonnull), # which triggers spurious warnings for our usage -- 2.9.3