GCC 7.1 introduces a new -Wformat-truncation warning flag that reports if it thinks the maximum possible size of the formatted output will exceed the provided fixed buffer. This is enabled automatically by the -Wformat warning flag. There are quite a few places hit by this in libvirt which need rewriting. This is non-trivial work in some places, so temporarily disable the new warning until those fixes can be implemented. Signed-off-by: Daniel P. Berrange <berrange(a)redhat.com&gt; --- m4/virt-compile-warnings.m4 | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/m4/virt-compile-warnings.m4 b/m4/virt-compile-warnings.m4 index d7bb172f3..fa0940fc6 100644 --- a/m4/virt-compile-warnings.m4 +++ b/m4/virt-compile-warnings.m4 @@ -169,6 +169,10 @@ AC_DEFUN([LIBVIRT_COMPILE_WARNINGS],[ wantwarn="$wantwarn -Wno-format" fi + # -Wformat enables this by default, and we should keep it, + # but need to rewrite various areas of code first + wantwarn="$wantwarn -Wno-format-truncation" + # This should be < 256 really. Currently we're down to 4096, # but using 1024 bytes sized buffers (mostly for virStrerror) # stops us from going down further -- 2.13.1