From 37f000c5aa76613e644cf3e5b1ec7bd2df6f7451 Mon Sep 17 00:00:00 2001 From: Ned Bass Date: Wed, 26 Dec 2012 14:56:41 -0800 Subject: [PATCH] Fix gcc array subscript above bounds warning In a debug build, certain GCC versions flag an array bounds warning in the below code from dnode_sync.c } else { int i; ASSERT(dn->dn_next_nblkptr[txgoff] < dnp->dn_nblkptr); /* the blkptrs we are losing better be unallocated */ for (i = dn->dn_next_nblkptr[txgoff]; i < dnp->dn_nblkptr; i++) ASSERT(BP_IS_HOLE(&dnp->dn_blkptr[i])); This usage is in fact safe, since the ASSERT ensures the index does not exceed to maximum possible number of block pointers. However gcc can't determine that the assignment 'i = dn->dn_next_nblkptr[txgoff];' falls within the array bounds so it issues a warning. To avoid this, initialize i to zero to make gcc happy but skip the elements before dn->dn_next_nblkptr[txgoff] in the loop body. Since a dnode contains at most 3 block pointers this overhead should be negligible. Signed-off-by: Brian Behlendorf Closes #950 --- module/zfs/dnode_sync.c | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-) diff --git a/module/zfs/dnode_sync.c b/module/zfs/dnode_sync.c index af636dcdb..f2dda867d 100644 --- a/module/zfs/dnode_sync.c +++ b/module/zfs/dnode_sync.c @@ -666,9 +666,10 @@ dnode_sync(dnode_t *dn, dmu_tx_t *tx) int i; ASSERT(dn->dn_next_nblkptr[txgoff] < dnp->dn_nblkptr); /* the blkptrs we are losing better be unallocated */ - for (i = dn->dn_next_nblkptr[txgoff]; - i < dnp->dn_nblkptr; i++) - ASSERT(BP_IS_HOLE(&dnp->dn_blkptr[i])); + for (i = 0; i < dnp->dn_nblkptr; i++) { + if (i >= dn->dn_next_nblkptr[txgoff]) + ASSERT(BP_IS_HOLE(&dnp->dn_blkptr[i])); + } #endif } mutex_enter(&dn->dn_mtx);