fix Go 1.7 pointer reference bug

This commit fixes a bug where page end-of-header pointers were being
converted to byte slices even when the pointer did not point to
allocated memory. This occurs with pages that have a `page.count`
of zero.

Note: This was not an issue in Go 1.6 but the new Go 1.7 SSA backend
handles `nil` checks differently.

See https://github.com/golang/go/issues/16772

1 files changed, 6 insertions, 0 deletions

diff --git a/page.go b/page.go
index 4a55528..7651a6b 100644
--- a/page.go
+++ b/page.go
@@ -62,6 +62,9 @@ func (p *page) leafPageElement(index uint16) *leafPageElement {
 
 // leafPageElements retrieves a list of leaf nodes.
 func (p *page) leafPageElements() []leafPageElement {
+	if p.count == 0 {
+		return nil
+	}
 	return ((*[0x7FFFFFF]leafPageElement)(unsafe.Pointer(&p.ptr)))[:]
 }
 
@@ -72,6 +75,9 @@ func (p *page) branchPageElement(index uint16) *branchPageElement {
 
 // branchPageElements retrieves a list of branch nodes.
 func (p *page) branchPageElements() []branchPageElement {
+	if p.count == 0 {
+		return nil
+	}
 	return ((*[0x7FFFFFF]branchPageElement)(unsafe.Pointer(&p.ptr)))[:]
 }