Fix unsafe pointer conversions caught by Go 1.14 checkptr

bolt_386.go

@@ -5,6 +5,3 @@ const maxMapSize = 0x7FFFFFFF // 2GB
 
 // maxAllocSize is the size used when creating array pointers.
 const maxAllocSize = 0xFFFFFFF
-
-// Are unaligned load/stores broken on this arch?
-var brokenUnaligned = false

bolt_amd64.go

@@ -5,6 +5,3 @@ const maxMapSize = 0xFFFFFFFFFFFF // 256TB
 
 // maxAllocSize is the size used when creating array pointers.
 const maxAllocSize = 0x7FFFFFFF
-
-// Are unaligned load/stores broken on this arch?
-var brokenUnaligned = false

bolt_arm.go

@@ -7,22 +7,3 @@ const maxMapSize = 0x7FFFFFFF // 2GB
 
 // maxAllocSize is the size used when creating array pointers.
 const maxAllocSize = 0xFFFFFFF
-
-// Are unaligned load/stores broken on this arch?
-var brokenUnaligned bool
-
-func init() {
-	// Simple check to see whether this arch handles unaligned load/stores
-	// correctly.
-
-	// ARM9 and older devices require load/stores to be from/to aligned
-	// addresses. If not, the lower 2 bits are cleared and that address is
-	// read in a jumbled up order.
-
-	// See http://infocenter.arm.com/help/index.jsp?topic=/com.arm.doc.faqs/ka15414.html
-
-	raw := [6]byte{0xfe, 0xef, 0x11, 0x22, 0x22, 0x11}
-	val := *(*uint32)(unsafe.Pointer(uintptr(unsafe.Pointer(&raw)) + 2))
-
-	brokenUnaligned = val != 0x11222211
-}

bolt_arm64.go

@@ -7,6 +7,3 @@ const maxMapSize = 0xFFFFFFFFFFFF // 256TB
 
 // maxAllocSize is the size used when creating array pointers.
 const maxAllocSize = 0x7FFFFFFF
-
-// Are unaligned load/stores broken on this arch?
-var brokenUnaligned = false

bolt_mips64x.go

@@ -7,6 +7,3 @@ const maxMapSize = 0x8000000000 // 512GB
 
 // maxAllocSize is the size used when creating array pointers.
 const maxAllocSize = 0x7FFFFFFF
-
-// Are unaligned load/stores broken on this arch?
-var brokenUnaligned = false

bolt_mipsx.go

@@ -7,6 +7,3 @@ const maxMapSize = 0x40000000 // 1GB
 
 // maxAllocSize is the size used when creating array pointers.
 const maxAllocSize = 0xFFFFFFF
-
-// Are unaligned load/stores broken on this arch?
-var brokenUnaligned = false

bolt_ppc.go

@@ -7,6 +7,3 @@ const maxMapSize = 0x7FFFFFFF // 2GB
 
 // maxAllocSize is the size used when creating array pointers.
 const maxAllocSize = 0xFFFFFFF
-
-// Are unaligned load/stores broken on this arch?
-var brokenUnaligned = false

bolt_ppc64.go

@@ -7,6 +7,3 @@ const maxMapSize = 0xFFFFFFFFFFFF // 256TB
 
 // maxAllocSize is the size used when creating array pointers.
 const maxAllocSize = 0x7FFFFFFF
-
-// Are unaligned load/stores broken on this arch?
-var brokenUnaligned = false

bolt_ppc64le.go

@@ -7,6 +7,3 @@ const maxMapSize = 0xFFFFFFFFFFFF // 256TB
 
 // maxAllocSize is the size used when creating array pointers.
 const maxAllocSize = 0x7FFFFFFF
-
-// Are unaligned load/stores broken on this arch?
-var brokenUnaligned = false

bolt_riscv64.go

@@ -7,6 +7,3 @@ const maxMapSize = 0xFFFFFFFFFFFF // 256TB
 
 // maxAllocSize is the size used when creating array pointers.
 const maxAllocSize = 0x7FFFFFFF
-
-// Are unaligned load/stores broken on this arch?
-var brokenUnaligned = true

bolt_s390x.go

@@ -7,6 +7,3 @@ const maxMapSize = 0xFFFFFFFFFFFF // 256TB
 
 // maxAllocSize is the size used when creating array pointers.
 const maxAllocSize = 0x7FFFFFFF
-
-// Are unaligned load/stores broken on this arch?
-var brokenUnaligned = false

bucket.go

@@ -123,10 +123,12 @@ func (b *Bucket) Bucket(name []byte) *Bucket {
 func (b *Bucket) openBucket(value []byte) *Bucket {
 	var child = newBucket(b.tx)
 
-	// If unaligned load/stores are broken on this arch and value is
+	// Unaligned access requires a copy to be made.
-	// unaligned simply clone to an aligned byte array.
+	const unalignedMask = unsafe.Alignof(struct {
-	unaligned := brokenUnaligned && uintptr(unsafe.Pointer(&value[0]))&3 != 0
+		bucket
-
+		page
+	}{}) - 1
+	unaligned := uintptr(unsafe.Pointer(&value[0]))&unalignedMask != 0
 	if unaligned {
 		value = cloneBytes(value)
 	}
@@ -409,7 +411,7 @@ func (b *Bucket) Stats() BucketStats {
 
 			if p.count != 0 {
 				// If page has any elements, add all element headers.
-				used += leafPageElementSize * int(p.count-1)
+				used += leafPageElementSize * uintptr(p.count-1)
 
 				// Add all element key, value sizes.
 				// The computation takes advantage of the fact that the position
@@ -417,16 +419,16 @@ func (b *Bucket) Stats() BucketStats {
 				// of all previous elements' keys and values.
 				// It also includes the last element's header.
 				lastElement := p.leafPageElement(p.count - 1)
-				used += int(lastElement.pos + lastElement.ksize + lastElement.vsize)
+				used += uintptr(lastElement.pos + lastElement.ksize + lastElement.vsize)
 			}
 
 			if b.root == 0 {
 				// For inlined bucket just update the inline stats
-				s.InlineBucketInuse += used
+				s.InlineBucketInuse += int(used)
 			} else {
 				// For non-inlined bucket update all the leaf stats
 				s.LeafPageN++
-				s.LeafInuse += used
+				s.LeafInuse += int(used)
 				s.LeafOverflowN += int(p.overflow)
 
 				// Collect stats from sub-buckets.
@@ -447,13 +449,13 @@ func (b *Bucket) Stats() BucketStats {
 
 			// used totals the used bytes for the page
 			// Add header and all element headers.
-			used := pageHeaderSize + (branchPageElementSize * int(p.count-1))
+			used := pageHeaderSize + (branchPageElementSize * uintptr(p.count-1))
 
 			// Add size of all keys and values.
 			// Again, use the fact that last element's position equals to
 			// the total of key, value sizes of all previous elements.
-			used += int(lastElement.pos + lastElement.ksize)
+			used += uintptr(lastElement.pos + lastElement.ksize)
-			s.BranchInuse += used
+			s.BranchInuse += int(used)
 			s.BranchOverflowN += int(p.overflow)
 		}
 
@@ -593,7 +595,7 @@ func (b *Bucket) inlineable() bool {
 	// our threshold for inline bucket size.
 	var size = pageHeaderSize
 	for _, inode := range n.inodes {
-		size += leafPageElementSize + len(inode.key) + len(inode.value)
+		size += leafPageElementSize + uintptr(len(inode.key)) + uintptr(len(inode.value))
 
 		if inode.flags&bucketLeafFlag != 0 {
 			return false
@@ -606,8 +608,8 @@ func (b *Bucket) inlineable() bool {
 }
 
 // Returns the maximum total size of a bucket to make it a candidate for inlining.
-func (b *Bucket) maxInlineBucketSize() int {
+func (b *Bucket) maxInlineBucketSize() uintptr {
-	return b.tx.db.pageSize / 4
+	return uintptr(b.tx.db.pageSize / 4)
 }
 
 // write allocates and writes a bucket to a byte slice.

db_test.go

@@ -1358,7 +1358,7 @@ func ExampleDB_View() {
 	// John's last name is doe.
 }
 
-func ExampleDB_Begin_ReadOnly() {
+func ExampleDB_Begin() {
 	// Open the database.
 	db, err := bolt.Open(tempfile(), 0666, nil)
 	if err != nil {

freelist.go

@@ -2,6 +2,7 @@ package bbolt
 
 import (
 	"fmt"
+	"reflect"
 	"sort"
 	"unsafe"
 )
@@ -71,7 +72,7 @@ func (f *freelist) size() int {
 		// The first element will be used to store the count. See freelist.write.
 		n++
 	}
-	return pageHeaderSize + (int(unsafe.Sizeof(pgid(0))) * n)
+	return int(pageHeaderSize) + (int(unsafe.Sizeof(pgid(0))) * n)
 }
 
 // count returns count of pages on the freelist
@@ -93,8 +94,24 @@ func (f *freelist) pending_count() int {
 	return count
 }
 
-// copyall copies into dst a list of all free ids and all pending ids in one sorted list.
+// copyallunsafe copies a list of all free ids and all pending ids in one sorted list.
 // f.count returns the minimum length required for dst.
+func (f *freelist) copyallunsafe(dstptr unsafe.Pointer) { // dstptr is []pgid data pointer
+	m := make(pgids, 0, f.pending_count())
+	for _, txp := range f.pending {
+		m = append(m, txp.ids...)
+	}
+	sort.Sort(m)
+	fpgids := f.getFreePageIDs()
+	sz := len(fpgids) + len(m)
+	dst := *(*[]pgid)(unsafe.Pointer(&reflect.SliceHeader{
+		Data: uintptr(dstptr),
+		Len:  sz,
+		Cap:  sz,
+	}))
+	mergepgids(dst, fpgids, m)
+}
+
 func (f *freelist) copyall(dst []pgid) {
 	m := make(pgids, 0, f.pending_count())
 	for _, txp := range f.pending {
@@ -267,17 +284,21 @@ func (f *freelist) read(p *page) {
 	}
 	// If the page.count is at the max uint16 value (64k) then it's considered
 	// an overflow and the size of the freelist is stored as the first element.
-	idx, count := 0, int(p.count)
+	var idx, count uintptr = 0, uintptr(p.count)
 	if count == 0xFFFF {
 		idx = 1
-		count = int(((*[maxAllocSize]pgid)(unsafe.Pointer(&p.ptr)))[0])
+		count = uintptr(*(*pgid)(unsafe.Pointer(uintptr(unsafe.Pointer(p)) + unsafe.Sizeof(*p))))
 	}
 
 	// Copy the list of page ids from the freelist.
 	if count == 0 {
 		f.ids = nil
 	} else {
-		ids := ((*[maxAllocSize]pgid)(unsafe.Pointer(&p.ptr)))[idx : idx+count]
+		ids := *(*[]pgid)(unsafe.Pointer(&reflect.SliceHeader{
+			Data: uintptr(unsafe.Pointer(p)) + unsafe.Sizeof(*p) + idx*unsafe.Sizeof(pgid(0)),
+			Len:  int(count),
+			Cap:  int(count),
+		}))
 
 		// copy the ids, so we don't modify on the freelist page directly
 		idsCopy := make([]pgid, count)
@@ -315,11 +336,11 @@ func (f *freelist) write(p *page) error {
 		p.count = uint16(lenids)
 	} else if lenids < 0xFFFF {
 		p.count = uint16(lenids)
-		f.copyall(((*[maxAllocSize]pgid)(unsafe.Pointer(&p.ptr)))[:])
+		f.copyallunsafe(unsafe.Pointer(uintptr(unsafe.Pointer(p)) + unsafe.Sizeof(*p)))
 	} else {
 		p.count = 0xFFFF
-		((*[maxAllocSize]pgid)(unsafe.Pointer(&p.ptr)))[0] = pgid(lenids)
+		*(*pgid)(unsafe.Pointer(uintptr(unsafe.Pointer(p)) + unsafe.Sizeof(*p))) = pgid(lenids)
-		f.copyall(((*[maxAllocSize]pgid)(unsafe.Pointer(&p.ptr)))[1:])
+		f.copyallunsafe(unsafe.Pointer(uintptr(unsafe.Pointer(p)) + unsafe.Sizeof(*p) + unsafe.Sizeof(pgid(0))))
 	}
 
 	return nil

freelist_test.go

@@ -262,7 +262,7 @@ func TestFreelist_read(t *testing.T) {
 	page.count = 2
 
 	// Insert 2 page ids.
-	ids := (*[3]pgid)(unsafe.Pointer(&page.ptr))
+	ids := (*[3]pgid)(unsafe.Pointer(uintptr(unsafe.Pointer(page)) + unsafe.Sizeof(*page)))
 	ids[0] = 23
 	ids[1] = 50
 

go.mod

@@ -1,3 +1,5 @@
 module go.etcd.io/bbolt
 
 go 1.12
+
+require golang.org/x/sys v0.0.0-20200202164722-d101bd2416d5

go.sum

@@ -0,0 +1,2 @@
+golang.org/x/sys v0.0.0-20200202164722-d101bd2416d5 h1:LfCXLvNmTYH9kEmVgqbnsWfruoXZIrh4YBgqVHtDvw0=
+golang.org/x/sys v0.0.0-20200202164722-d101bd2416d5/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=

node.go

@@ -3,6 +3,7 @@ package bbolt
 import (
 	"bytes"
 	"fmt"
+	"reflect"
 	"sort"
 	"unsafe"
 )
@@ -41,19 +42,19 @@ func (n *node) size() int {
 	sz, elsz := pageHeaderSize, n.pageElementSize()
 	for i := 0; i < len(n.inodes); i++ {
 		item := &n.inodes[i]
-		sz += elsz + len(item.key) + len(item.value)
+		sz += elsz + uintptr(len(item.key)) + uintptr(len(item.value))
 	}
-	return sz
+	return int(sz)
 }
 
 // sizeLessThan returns true if the node is less than a given size.
 // This is an optimization to avoid calculating a large node when we only need
 // to know if it fits inside a certain page size.
-func (n *node) sizeLessThan(v int) bool {
+func (n *node) sizeLessThan(v uintptr) bool {
 	sz, elsz := pageHeaderSize, n.pageElementSize()
 	for i := 0; i < len(n.inodes); i++ {
 		item := &n.inodes[i]
-		sz += elsz + len(item.key) + len(item.value)
+		sz += elsz + uintptr(len(item.key)) + uintptr(len(item.value))
 		if sz >= v {
 			return false
 		}
@@ -62,7 +63,7 @@ func (n *node) sizeLessThan(v int) bool {
 }
 
 // pageElementSize returns the size of each page element based on the type of node.
-func (n *node) pageElementSize() int {
+func (n *node) pageElementSize() uintptr {
 	if n.isLeaf {
 		return leafPageElementSize
 	}
@@ -207,39 +208,39 @@ func (n *node) write(p *page) {
 	}
 
 	// Loop over each item and write it to the page.
-	b := (*[maxAllocSize]byte)(unsafe.Pointer(&p.ptr))[n.pageElementSize()*len(n.inodes):]
+	bp := uintptr(unsafe.Pointer(p)) + unsafe.Sizeof(*p) + n.pageElementSize()*uintptr(len(n.inodes))
 	for i, item := range n.inodes {
 		_assert(len(item.key) > 0, "write: zero-length inode key")
 
 		// Write the page element.
 		if n.isLeaf {
 			elem := p.leafPageElement(uint16(i))
-			elem.pos = uint32(uintptr(unsafe.Pointer(&b[0])) - uintptr(unsafe.Pointer(elem)))
+			elem.pos = uint32(bp - uintptr(unsafe.Pointer(elem)))
 			elem.flags = item.flags
 			elem.ksize = uint32(len(item.key))
 			elem.vsize = uint32(len(item.value))
 		} else {
 			elem := p.branchPageElement(uint16(i))
-			elem.pos = uint32(uintptr(unsafe.Pointer(&b[0])) - uintptr(unsafe.Pointer(elem)))
+			elem.pos = uint32(bp - uintptr(unsafe.Pointer(elem)))
 			elem.ksize = uint32(len(item.key))
 			elem.pgid = item.pgid
 			_assert(elem.pgid != p.id, "write: circular dependency occurred")
 		}
 
-		// If the length of key+value is larger than the max allocation size
+		// Create a slice to write into of needed size and advance
-		// then we need to reallocate the byte array pointer.
+		// byte pointer for next iteration.
-		//
-		// See: https://github.com/boltdb/bolt/pull/335
 		klen, vlen := len(item.key), len(item.value)
-		if len(b) < klen+vlen {
+		sz := klen + vlen
-			b = (*[maxAllocSize]byte)(unsafe.Pointer(&b[0]))[:]
+		b := *(*[]byte)(unsafe.Pointer(&reflect.SliceHeader{
-		}
+			Data: bp,
+			Len:  sz,
+			Cap:  sz,
+		}))
+		bp += uintptr(sz)
 
 		// Write data for the element to the end of the page.
-		copy(b[0:], item.key)
+		l := copy(b, item.key)
-		b = b[klen:]
+		copy(b[l:], item.value)
-		copy(b[0:], item.value)
-		b = b[vlen:]
 	}
 
 	// DEBUG ONLY: n.dump()
@@ -247,7 +248,7 @@ func (n *node) write(p *page) {
 
 // split breaks up a node into multiple smaller nodes, if appropriate.
 // This should only be called from the spill() function.
-func (n *node) split(pageSize int) []*node {
+func (n *node) split(pageSize uintptr) []*node {
 	var nodes []*node
 
 	node := n
@@ -270,7 +271,7 @@ func (n *node) split(pageSize int) []*node {
 
 // splitTwo breaks up a node into two smaller nodes, if appropriate.
 // This should only be called from the split() function.
-func (n *node) splitTwo(pageSize int) (*node, *node) {
+func (n *node) splitTwo(pageSize uintptr) (*node, *node) {
 	// Ignore the split if the page doesn't have at least enough nodes for
 	// two pages or if the nodes can fit in a single page.
 	if len(n.inodes) <= (minKeysPerPage*2) || n.sizeLessThan(pageSize) {
@@ -312,18 +313,18 @@ func (n *node) splitTwo(pageSize int) (*node, *node) {
 // splitIndex finds the position where a page will fill a given threshold.
 // It returns the index as well as the size of the first page.
 // This is only be called from split().
-func (n *node) splitIndex(threshold int) (index, sz int) {
+func (n *node) splitIndex(threshold int) (index, sz uintptr) {
 	sz = pageHeaderSize
 
 	// Loop until we only have the minimum number of keys required for the second page.
 	for i := 0; i < len(n.inodes)-minKeysPerPage; i++ {
-		index = i
+		index = uintptr(i)
 		inode := n.inodes[i]
-		elsize := n.pageElementSize() + len(inode.key) + len(inode.value)
+		elsize := n.pageElementSize() + uintptr(len(inode.key)) + uintptr(len(inode.value))
 
 		// If we have at least the minimum number of keys and adding another
 		// node would put us over the threshold then exit and return.
-		if i >= minKeysPerPage && sz+elsize > threshold {
+		if index >= minKeysPerPage && sz+elsize > uintptr(threshold) {
 			break
 		}
 
@@ -356,7 +357,7 @@ func (n *node) spill() error {
 	n.children = nil
 
 	// Split nodes into appropriate sizes. The first node will always be n.
-	var nodes = n.split(tx.db.pageSize)
+	var nodes = n.split(uintptr(tx.db.pageSize))
 	for _, node := range nodes {
 		// Add node's page to the freelist if it's not new.
 		if node.pgid > 0 {
@@ -587,9 +588,11 @@ func (n *node) dump() {
 
 type nodes []*node
 
-func (s nodes) Len() int           { return len(s) }
+func (s nodes) Len() int      { return len(s) }
-func (s nodes) Swap(i, j int)      { s[i], s[j] = s[j], s[i] }
+func (s nodes) Swap(i, j int) { s[i], s[j] = s[j], s[i] }
-func (s nodes) Less(i, j int) bool { return bytes.Compare(s[i].inodes[0].key, s[j].inodes[0].key) == -1 }
+func (s nodes) Less(i, j int) bool {
+	return bytes.Compare(s[i].inodes[0].key, s[j].inodes[0].key) == -1
+}
 
 // inode represents an internal node inside of a node.
 // It can be used to point to elements in a page or point

node_test.go

@@ -39,7 +39,7 @@ func TestNode_read_LeafPage(t *testing.T) {
 	page.count = 2
 
 	// Insert 2 elements at the beginning. sizeof(leafPageElement) == 16
-	nodes := (*[3]leafPageElement)(unsafe.Pointer(&page.ptr))
+	nodes := (*[3]leafPageElement)(unsafe.Pointer(uintptr(unsafe.Pointer(page)) + unsafe.Sizeof(*page)))
 	nodes[0] = leafPageElement{flags: 0, pos: 32, ksize: 3, vsize: 4}  // pos = sizeof(leafPageElement) * 2
 	nodes[1] = leafPageElement{flags: 0, pos: 23, ksize: 10, vsize: 3} // pos = sizeof(leafPageElement) + 3 + 4
 

page.go

@@ -3,16 +3,17 @@ package bbolt
 import (
 	"fmt"
 	"os"
+	"reflect"
 	"sort"
 	"unsafe"
 )
 
-const pageHeaderSize = int(unsafe.Offsetof(((*page)(nil)).ptr))
+const pageHeaderSize = unsafe.Sizeof(page{})
 
 const minKeysPerPage = 2
 
-const branchPageElementSize = int(unsafe.Sizeof(branchPageElement{}))
+const branchPageElementSize = unsafe.Sizeof(branchPageElement{})
-const leafPageElementSize = int(unsafe.Sizeof(leafPageElement{}))
+const leafPageElementSize = unsafe.Sizeof(leafPageElement{})
 
 const (
 	branchPageFlag   = 0x01
@@ -32,7 +33,6 @@ type page struct {
 	flags    uint16
 	count    uint16
 	overflow uint32
-	ptr      uintptr
 }
 
 // typ returns a human readable page type string used for debugging.
@@ -51,13 +51,13 @@ func (p *page) typ() string {
 
 // meta returns a pointer to the metadata section of the page.
 func (p *page) meta() *meta {
-	return (*meta)(unsafe.Pointer(&p.ptr))
+	return (*meta)(unsafe.Pointer(uintptr(unsafe.Pointer(p)) + unsafe.Sizeof(*p)))
 }
 
 // leafPageElement retrieves the leaf node by index
 func (p *page) leafPageElement(index uint16) *leafPageElement {
-	n := &((*[0x7FFFFFF]leafPageElement)(unsafe.Pointer(&p.ptr)))[index]
+	off := uintptr(index) * unsafe.Sizeof(leafPageElement{})
-	return n
+	return (*leafPageElement)(unsafe.Pointer(uintptr(unsafe.Pointer(p)) + unsafe.Sizeof(*p) + off))
 }
 
 // leafPageElements retrieves a list of leaf nodes.
@@ -65,12 +65,17 @@ func (p *page) leafPageElements() []leafPageElement {
 	if p.count == 0 {
 		return nil
 	}
-	return ((*[0x7FFFFFF]leafPageElement)(unsafe.Pointer(&p.ptr)))[:]
+	return *(*[]leafPageElement)(unsafe.Pointer(&reflect.SliceHeader{
+		Data: uintptr(unsafe.Pointer(p)) + unsafe.Sizeof(*p),
+		Len:  int(p.count),
+		Cap:  int(p.count),
+	}))
 }
 
 // branchPageElement retrieves the branch node by index
 func (p *page) branchPageElement(index uint16) *branchPageElement {
-	return &((*[0x7FFFFFF]branchPageElement)(unsafe.Pointer(&p.ptr)))[index]
+	off := uintptr(index) * unsafe.Sizeof(branchPageElement{})
+	return (*branchPageElement)(unsafe.Pointer(uintptr(unsafe.Pointer(p)) + unsafe.Sizeof(*p) + off))
 }
 
 // branchPageElements retrieves a list of branch nodes.
@@ -78,12 +83,20 @@ func (p *page) branchPageElements() []branchPageElement {
 	if p.count == 0 {
 		return nil
 	}
-	return ((*[0x7FFFFFF]branchPageElement)(unsafe.Pointer(&p.ptr)))[:]
+	return *(*[]branchPageElement)(unsafe.Pointer(&reflect.SliceHeader{
+		Data: uintptr(unsafe.Pointer(p)) + unsafe.Sizeof(*p),
+		Len:  int(p.count),
+		Cap:  int(p.count),
+	}))
 }
 
 // dump writes n bytes of the page to STDERR as hex output.
 func (p *page) hexdump(n int) {
-	buf := (*[maxAllocSize]byte)(unsafe.Pointer(p))[:n]
+	buf := *(*[]byte)(unsafe.Pointer(&reflect.SliceHeader{
+		Data: uintptr(unsafe.Pointer(p)),
+		Len:  n,
+		Cap:  n,
+	}))
 	fmt.Fprintf(os.Stderr, "%x\n", buf)
 }
 
@@ -102,8 +115,11 @@ type branchPageElement struct {
 
 // key returns a byte slice of the node key.
 func (n *branchPageElement) key() []byte {
-	buf := (*[maxAllocSize]byte)(unsafe.Pointer(n))
+	return *(*[]byte)(unsafe.Pointer(&reflect.SliceHeader{
-	return (*[maxAllocSize]byte)(unsafe.Pointer(&buf[n.pos]))[:n.ksize]
+		Data: uintptr(unsafe.Pointer(n)) + uintptr(n.pos),
+		Len:  int(n.ksize),
+		Cap:  int(n.ksize),
+	}))
 }
 
 // leafPageElement represents a node on a leaf page.
@@ -116,14 +132,20 @@ type leafPageElement struct {
 
 // key returns a byte slice of the node key.
 func (n *leafPageElement) key() []byte {
-	buf := (*[maxAllocSize]byte)(unsafe.Pointer(n))
+	return *(*[]byte)(unsafe.Pointer(&reflect.SliceHeader{
-	return (*[maxAllocSize]byte)(unsafe.Pointer(&buf[n.pos]))[:n.ksize:n.ksize]
+		Data: uintptr(unsafe.Pointer(n)) + uintptr(n.pos),
+		Len:  int(n.ksize),
+		Cap:  int(n.ksize),
+	}))
 }
 
 // value returns a byte slice of the node value.
 func (n *leafPageElement) value() []byte {
-	buf := (*[maxAllocSize]byte)(unsafe.Pointer(n))
+	return *(*[]byte)(unsafe.Pointer(&reflect.SliceHeader{
-	return (*[maxAllocSize]byte)(unsafe.Pointer(&buf[n.pos+n.ksize]))[:n.vsize:n.vsize]
+		Data: uintptr(unsafe.Pointer(n)) + uintptr(n.pos) + uintptr(n.ksize),
+		Len:  int(n.vsize),
+		Cap:  int(n.vsize),
+	}))
 }
 
 // PageInfo represents human readable information about a page.

tx.go

@@ -4,6 +4,7 @@ import (
 	"fmt"
 	"io"
 	"os"
+	"reflect"
 	"sort"
 	"strings"
 	"time"
@@ -527,7 +528,7 @@ func (tx *Tx) write() error {
 		offset := int64(p.id) * int64(tx.db.pageSize)
 
 		// Write out page in "max allocation" sized chunks.
-		ptr := (*[maxAllocSize]byte)(unsafe.Pointer(p))
+		ptr := uintptr(unsafe.Pointer(p))
 		for {
 			// Limit our write to our max allocation size.
 			sz := size
@@ -536,7 +537,11 @@ func (tx *Tx) write() error {
 			}
 
 			// Write chunk to disk.
-			buf := ptr[:sz]
+			buf := *(*[]byte)(unsafe.Pointer(&reflect.SliceHeader{
+				Data: ptr,
+				Len:  sz,
+				Cap:  sz,
+			}))
 			if _, err := tx.db.ops.writeAt(buf, offset); err != nil {
 				return err
 			}
@@ -552,7 +557,7 @@ func (tx *Tx) write() error {
 
 			// Otherwise move offset forward and move pointer to next chunk.
 			offset += int64(sz)
-			ptr = (*[maxAllocSize]byte)(unsafe.Pointer(&ptr[sz]))
+			ptr += uintptr(sz)
 		}
 	}
 
@@ -571,7 +576,11 @@ func (tx *Tx) write() error {
 			continue
 		}
 
-		buf := (*[maxAllocSize]byte)(unsafe.Pointer(p))[:tx.db.pageSize]
+		buf := *(*[]byte)(unsafe.Pointer(&reflect.SliceHeader{
+			Data: uintptr(unsafe.Pointer(p)),
+			Len:  tx.db.pageSize,
+			Cap:  tx.db.pageSize,
+		}))
 
 		// See https://go.googlesource.com/go/+/f03c9202c43e0abb130669852082117ca50aa9b1
 		for i := range buf {