[PATCH 6/6] kbuild: Enable -Wtautological-compare

From: Nathan Chancellor
Date: Tue Feb 18 2020 - 23:54:47 EST

Currently, we disable -Wtautological-compare, which in turn disables a
bunch of more specific tautological comparison warnings that are useful
for the kernel (see clang's documentation below). Now that all of the
major/noisy warnings have been fixed, enable -Wtautological-compare so
that more issues can be caught at build time.

-Wtautological-constant-out-of-range-compare is kept disabled because
there are places in the kernel where a constant or variable size can
change based on the kernel configuration; these are not fixed in a
clean/concise way and they are almost always harmless so this one
subwarning is kept disabled.

Link: https://github.com/ClangBuiltLinux/linux/issues/488
Link: http://releases.llvm.org/9.0.0/tools/clang/docs/DiagnosticsReference.html#wtautological-compare
Signed-off-by: Nathan Chancellor <natechancellor@xxxxxxxxx>
Makefile | 3 +--
1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/Makefile b/Makefile
index b954c304c479..99080c57a1cb 100644
--- a/Makefile
+++ b/Makefile
@@ -742,8 +742,7 @@ ifdef CONFIG_CC_IS_CLANG
KBUILD_CPPFLAGS += -Qunused-arguments
KBUILD_CFLAGS += -Wno-format-invalid-specifier
-# Quiet clang warning: comparison of unsigned expression < 0 is always false
-KBUILD_CFLAGS += -Wno-tautological-compare
+KBUILD_CFLAGS += -Wno-tautological-constant-out-of-range-compare
# CLANG uses a _MergedGlobals as optimization, but this breaks modpost, as the
# source of a reference will be _MergedGlobals and not on of the whitelisted names.
# See modpost pattern 2