On Wed, 29 Nov 2017, Alex Richardson wrote:
Log:
Don't fail the build due to clang integer constant range warnings
This warning checks whether a constant is out of range of the integer
type. An example is `comparison of 'u_int' > 4294967295 is always false`
and in this case the warning makes sense.
However, when the type is a typedef that can be either 64 or 32 bits the
if condition is only tautological in some configurations so this should
not be a warning that fails the build.
Even when the type is not a typedef, its limits are MD (except POSIX
specifies precise limits for unsigned char and signed char).
Reviewed by: dim
Approved by: jhb (mentor)
Differential Revision: https://reviews.freebsd.org/D12912
Modified:
head/share/mk/bsd.sys.mk
Modified: head/share/mk/bsd.sys.mk
==============================================================================
--- head/share/mk/bsd.sys.mk Wed Nov 29 20:44:40 2017 (r326374)
+++ head/share/mk/bsd.sys.mk Wed Nov 29 21:16:14 2017 (r326375)
@@ -81,6 +81,9 @@ CWARNFLAGS.clang+= -Wno-unused-local-typedef
.if ${COMPILER_TYPE} == "clang" && ${COMPILER_VERSION} >= 40000
CWARNFLAGS.clang+= -Wno-address-of-packed-member
.endif
+.if ${COMPILER_TYPE} == "clang" && ${COMPILER_VERSION} >= 60000
+CWARNFLAGS.clang+= -Wno-error=tautological-constant-compare
+.endif
.endif # WARNS <= 3
.if ${WARNS} <= 2
CWARNFLAGS.clang+= -Wno-switch -Wno-switch-enum -Wno-knr-promoted-parameter
But this breaks the warning in all cases.
There are related problems for signedness, especially for typedefed
types and plain char. Robust code must not assume any particular
signedness unless the type is documented as unsigned integral, so it
checks for < 0. Then if compilers warn about tautological comparisons
with 0, the warnings are usually "fixed" by removing the checks. Then
if the type or typedef is changed to signed, the code breaks. It is
better to break the warning as above.
Bruce
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