Messages in this thread | | | Date | Thu, 17 Sep 2009 16:24:37 -0700 | From | Andrew Morton <> | Subject | Re: [PATCH] fix BUILD_BUG_ON() and a couple of bogus uses of it |
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On Tue, 18 Aug 2009 16:59:25 +0100 "Jan Beulich" <JBeulich@novell.com> wrote:
> gcc permitting variable length arrays makes the current construct > used for BUILD_BUG_ON() useless, as that doesn't produce any diagnostic > if the controlling expression isn't really constant. Instead, this > patch makes it so that a bit field gets used here. Consequently, those > uses where the condition isn't really constant now also need fixing. > > Note that in the gfp.h, kmemcheck.h, and virtio_config.h cases > MAYBE_BUILD_BUG_ON() really just serves documentation purposes - even > if the expression is compile time constant (__builtin_constant_p() > yields true), the array is still deemed of variable length by gcc, and > hence the whole expression doesn't have the intended effect.
sparc64:
In file included from arch/sparc/kernel/vio.c:17: /usr/src/devel/arch/sparc/include/asm/vio.h: In function `vio_dring_avail': /usr/src/devel/arch/sparc/include/asm/vio.h:261: error: bit-field `<anonymous>' width not an integer constant
static inline u32 vio_dring_avail(struct vio_dring_state *dr, unsigned int ring_size) { BUILD_BUG_ON(!is_power_of_2(ring_size));
return (dr->pending - ((dr->prod - dr->cons) & (ring_size - 1))); }
changing it to MAYBE_BUILD_BUG_ON seems to have fixed it.
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