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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>
1 parent 1fe72ea commit 8c87df457cb58fe75b9b893007917cf8095660a0 Jan Beulich committed with Sep 22, 2009
@@ -258,7 +258,7 @@ static inline void *vio_dring_entry(struct vio_dring_state *dr,
static inline u32 vio_dring_avail(struct vio_dring_state *dr,
unsigned int ring_size)
{
- BUILD_BUG_ON(!is_power_of_2(ring_size));
+ MAYBE_BUILD_BUG_ON(!is_power_of_2(ring_size));
return (dr->pending -
((dr->prod - dr->cons) & (ring_size - 1)));
View
@@ -696,7 +696,7 @@ int __tpm_pcr_read(struct tpm_chip *chip, int pcr_idx, u8 *res_buf)
cmd.header.in = pcrread_header;
cmd.params.pcrread_in.pcr_idx = cpu_to_be32(pcr_idx);
- BUILD_BUG_ON(cmd.header.in.length > READ_PCR_RESULT_SIZE);
+ BUG_ON(cmd.header.in.length > READ_PCR_RESULT_SIZE);
rc = transmit_cmd(chip, &cmd, cmd.header.in.length,
"attempting to read a pcr value");
@@ -760,7 +760,7 @@ int tpm_pcr_extend(u32 chip_num, int pcr_idx, const u8 *hash)
return -ENODEV;
cmd.header.in = pcrextend_header;
- BUILD_BUG_ON(be32_to_cpu(cmd.header.in.length) > EXTEND_PCR_SIZE);
+ BUG_ON(be32_to_cpu(cmd.header.in.length) > EXTEND_PCR_SIZE);
cmd.params.pcrextend_in.pcr_idx = cpu_to_be32(pcr_idx);
memcpy(cmd.params.pcrextend_in.hash, hash, TPM_DIGEST_SIZE);
rc = transmit_cmd(chip, &cmd, cmd.header.in.length,
View
@@ -5615,7 +5615,7 @@ static void niu_init_tx_mac(struct niu *np)
/* The XMAC_MIN register only accepts values for TX min which
* have the low 3 bits cleared.
*/
- BUILD_BUG_ON(min & 0x7);
+ BUG_ON(min & 0x7);
if (np->flags & NIU_FLAGS_XMAC)
niu_init_tx_xmac(np, min, max);
View
@@ -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);
View
@@ -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__)
@@ -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)
@@ -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);

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