configure: Compile with -Wimplicit-fallthrough=2

Coverity always complains about switch-case statements that fall through
the next one when there is no comment in between - which could indicate
a forgotten "break" statement. Instead of handling these issues after
they have been committed, it would be better to avoid them in the build
process already. Thus let's enable the -Wimplicit-fallthrough warning now.
The "=2" level seems to be a good compromise between being too strict and
too generic about the possible comments, so we'll start with "=2" for now.

Signed-off-by: Thomas Huth <thuth@redhat.com>
Reviewed-by: Chen Qun <kuhn.chenqun@huawei.com>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Message-Id: <20201211152426.350966-13-thuth@redhat.com>
Signed-off-by: Thomas Huth <thuth@redhat.com>

diff --git a/configure b/configure
index c228f7c21e7578a06f70723fd4d26781b4b7ec59..881af4b6beaa5d7ee6953a5f82aa14f64ee55ec1 100755 (executable)
--- a/configure
+++ b/configure
@@ -2023,6 +2023,7 @@ add_to warn_flags -Wempty-body
 add_to warn_flags -Wnested-externs
 add_to warn_flags -Wendif-labels
 add_to warn_flags -Wexpansion-to-defined
+add_to warn_flags -Wimplicit-fallthrough=2
 
 nowarn_flags=
 add_to nowarn_flags -Wno-initializer-overrides