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authorJan Beulich <JBeulich@novell.com>2009-09-22 16:43:52 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2009-09-23 07:39:29 -0700
commit8c87df457cb58fe75b9b893007917cf8095660a0 (patch)
tree32446b329e4b83ae6158fa1505c36634a75dbfe8 /include
parent1fe72eaa0f46a0fa4cdcd8f3f7853b6d39469784 (diff)
BUILD_BUG_ON(): fix it and a couple of bogus uses of it
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. [akpm@linux-foundation.org: make arch/sparc/include/asm/vio.h compile] [akpm@linux-foundation.org: more nonsensical assertions in tpm.c..] Signed-off-by: Jan Beulich <jbeulich@novell.com> Cc: Andi Kleen <andi@firstfloor.org> Cc: Rusty Russell <rusty@rustcorp.com.au> Cc: Catalin Marinas <catalin.marinas@arm.com> Cc: "David S. Miller" <davem@davemloft.net> Cc: Rajiv Andrade <srajiv@linux.vnet.ibm.com> Cc: Mimi Zohar <zohar@us.ibm.com> Cc: James Morris <jmorris@namei.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'include')
-rw-r--r--include/linux/gfp.h2
-rw-r--r--include/linux/kernel.h8
-rw-r--r--include/linux/kmemcheck.h2
-rw-r--r--include/linux/virtio_config.h3
4 files changed, 9 insertions, 6 deletions
diff --git a/include/linux/gfp.h b/include/linux/gfp.h
index f53e9b868c2..557bdad320b 100644
--- a/include/linux/gfp.h
+++ b/include/linux/gfp.h
@@ -220,7 +220,7 @@ static inline enum zone_type gfp_zone(gfp_t flags)
((1 << ZONES_SHIFT) - 1);
if (__builtin_constant_p(bit))
- BUILD_BUG_ON((GFP_ZONE_BAD >> bit) & 1);
+ MAYBE_BUILD_BUG_ON((GFP_ZONE_BAD >> bit) & 1);
else {
#ifdef CONFIG_DEBUG_VM
BUG_ON((GFP_ZONE_BAD >> bit) & 1);
diff --git a/include/linux/kernel.h b/include/linux/kernel.h
index 55723afa097..63dcaece1ac 100644
--- a/include/linux/kernel.h
+++ b/include/linux/kernel.h
@@ -678,13 +678,17 @@ struct sysinfo {
};
/* Force a compilation error if condition is true */
-#define BUILD_BUG_ON(condition) ((void)sizeof(char[1 - 2*!!(condition)]))
+#define BUILD_BUG_ON(condition) ((void)BUILD_BUG_ON_ZERO(condition))
+
+/* Force a compilation error if condition is constant and true */
+#define MAYBE_BUILD_BUG_ON(cond) ((void)sizeof(char[1 - 2 * !!(cond)]))
/* Force a compilation error if condition is true, but also produce a
result (of value 0 and type size_t), so the expression can be used
e.g. in a structure initializer (or where-ever else comma expressions
aren't permitted). */
-#define BUILD_BUG_ON_ZERO(e) (sizeof(char[1 - 2 * !!(e)]) - 1)
+#define BUILD_BUG_ON_ZERO(e) (sizeof(struct { int:-!!(e); }))
+#define BUILD_BUG_ON_NULL(e) ((void *)sizeof(struct { int:-!!(e); }))
/* Trap pasters of __FUNCTION__ at compile-time */
#define __FUNCTION__ (__func__)
diff --git a/include/linux/kmemcheck.h b/include/linux/kmemcheck.h
index 136cdcdf92e..e880d4cf9e2 100644
--- a/include/linux/kmemcheck.h
+++ b/include/linux/kmemcheck.h
@@ -152,7 +152,7 @@ static inline bool kmemcheck_is_obj_initialized(unsigned long addr, size_t size)
\
_n = (long) &((ptr)->name##_end) \
- (long) &((ptr)->name##_begin); \
- BUILD_BUG_ON(_n < 0); \
+ MAYBE_BUILD_BUG_ON(_n < 0); \
\
kmemcheck_mark_initialized(&((ptr)->name##_begin), _n); \
} while (0)
diff --git a/include/linux/virtio_config.h b/include/linux/virtio_config.h
index e547e3c8ee9..0093dd7c1d6 100644
--- a/include/linux/virtio_config.h
+++ b/include/linux/virtio_config.h
@@ -109,8 +109,7 @@ static inline bool virtio_has_feature(const struct virtio_device *vdev,
unsigned int fbit)
{
/* Did you forget to fix assumptions on max features? */
- if (__builtin_constant_p(fbit))
- BUILD_BUG_ON(fbit >= 32);
+ MAYBE_BUILD_BUG_ON(fbit >= 32);
if (fbit < VIRTIO_TRANSPORT_F_START)
virtio_check_driver_offered_feature(vdev, fbit);