Messages in this thread | | | From | David Laight <> | Subject | RE: [PATCH] ARM: delay: avoid clang -Wtautological-constant warning | Date | Wed, 24 Mar 2021 23:14:40 +0000 |
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From: Arnd Bergmann > Sent: 23 March 2021 13:20 > Passing an 8-bit constant into delay() triggers a warning when building > with 'make W=1' using clang: > > drivers/clk/actions/owl-pll.c:182:2: error: result of comparison of constant 2000 with expression of > type 'u8' (aka 'unsigned char') is always false [-Werror,-Wtautological-constant-out-of-range-compare] > udelay(pll_hw->delay); > ^~~~~~~~~~~~~~~~~~~~~ > arch/arm/include/asm/delay.h:84:9: note: expanded from macro 'udelay' > ((n) > (MAX_UDELAY_MS * 1000) ? __bad_udelay() : \ > ~~~ ^ ~~~~~~~~~~~~~~~~~~~~~~ > arch/arm/mach-omap2/wd_timer.c:89:3: error: result of comparison of constant 2000 with expression of > type 'u8' (aka 'unsigned char') is always false [-Werror,-Wtautological-constant-out-of-range-compare] > udelay(oh->class->sysc->srst_udelay); > ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ > > Shut up the warning by adding a cast to a 64-bit number. A cast to 'int' > would usually be sufficient, but would fail to cause a link-time error > for large 64-bit constants.
Adding 0u probably has the desired effect - without any side effects of a cast.
David
> > Signed-off-by: Arnd Bergmann <arnd@arndb.de> > --- > arch/arm/include/asm/delay.h | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/arch/arm/include/asm/delay.h b/arch/arm/include/asm/delay.h > index 4f80b72372b4..1bb6417a3a83 100644 > --- a/arch/arm/include/asm/delay.h > +++ b/arch/arm/include/asm/delay.h > @@ -81,7 +81,7 @@ extern void __bad_udelay(void); > > #define udelay(n) \ > (__builtin_constant_p(n) ? \ > - ((n) > (MAX_UDELAY_MS * 1000) ? __bad_udelay() : \ > + ((u64)(n) > (MAX_UDELAY_MS * 1000) ? __bad_udelay() : \ > __const_udelay((n) * UDELAY_MULT)) : \ > __udelay(n)) > > -- > 2.29.2
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