handles, merge, odb: changes for Go 1.6 pointer passing rules

See http://tip.golang.org/cmd/cgo/#hdr-Passing_pointers .

handles.go

@@ -52,12 +52,12 @@ func (v *HandleList) Track(pointer interface{}) unsafe.Pointer {
 
 	v.Unlock()
 
-	return unsafe.Pointer(&slot)
+	return unsafe.Pointer(uintptr(slot))
 }
 
 // Untrack stops tracking the pointer given by the handle
 func (v *HandleList) Untrack(handle unsafe.Pointer) {
-	slot := *(*int)(handle)
+	slot := int(uintptr(handle))
 
 	v.Lock()
 
@@ -69,7 +69,7 @@ func (v *HandleList) Untrack(handle unsafe.Pointer) {
 
 // Get retrieves the pointer from the given handle
 func (v *HandleList) Get(handle unsafe.Pointer) interface{} {
-	slot := *(*int)(handle)
+	slot := int(uintptr(handle))
 
 	v.RLock()
 

merge.go

@@ -262,7 +262,7 @@ func (r *Repository) MergeBases(one, two *Oid) ([]*Oid, error) {
 	}
 
 	oids := make([]*Oid, coids.count)
-	hdr := reflect.SliceHeader {
+	hdr := reflect.SliceHeader{
 		Data: uintptr(unsafe.Pointer(coids.ids)),
 		Len:  int(coids.count),
 		Cap:  int(coids.count),
@@ -321,17 +321,21 @@ type MergeFileInput struct {
 }
 
 // populate a C struct with merge file input, make sure to use freeMergeFileInput to clean up allocs
-func populateCMergeFileInput(c *C.git_merge_file_input, input MergeFileInput) {
+func populateCMergeFileInput(c *C.git_merge_file_input, input MergeFileInput) *C.char {
 	c.path = C.CString(input.Path)
+	var toFree *C.char
 	if input.Contents != nil {
-		c.ptr = (*C.char)(unsafe.Pointer(&input.Contents[0]))
+		toFree = C.CString(string(input.Contents))
+		c.ptr = toFree
 		c.size = C.size_t(len(input.Contents))
 	}
 	c.mode = C.uint(input.Mode)
+	return toFree
 }
 
-func freeCMergeFileInput(c *C.git_merge_file_input) {
+func freeCMergeFileInput(c *C.git_merge_file_input, toFree *C.char) {
 	C.free(unsafe.Pointer(c.path))
+	C.free(unsafe.Pointer(toFree))
 }
 
 type MergeFileFlags int
@@ -382,12 +386,12 @@ func MergeFile(ancestor MergeFileInput, ours MergeFileInput, theirs MergeFileInp
 	var cours C.git_merge_file_input
 	var ctheirs C.git_merge_file_input
 
-	populateCMergeFileInput(&cancestor, ancestor)
-	defer freeCMergeFileInput(&cancestor)
-	populateCMergeFileInput(&cours, ours)
-	defer freeCMergeFileInput(&cours)
-	populateCMergeFileInput(&ctheirs, theirs)
-	defer freeCMergeFileInput(&ctheirs)
+	t := populateCMergeFileInput(&cancestor, ancestor)
+	defer freeCMergeFileInput(&cancestor, t)
+	t = populateCMergeFileInput(&cours, ours)
+	defer freeCMergeFileInput(&cours, t)
+	t = populateCMergeFileInput(&ctheirs, theirs)
+	defer freeCMergeFileInput(&ctheirs, t)
 
 	var copts *C.git_merge_file_options
 	if options != nil {

odb.go

@@ -61,12 +61,13 @@ func (v *Odb) Exists(oid *Oid) bool {
 
 func (v *Odb) Write(data []byte, otype ObjectType) (oid *Oid, err error) {
 	oid = new(Oid)
-	hdr := (*reflect.SliceHeader)(unsafe.Pointer(&data))
+	cstr := C.CString(string(data))
+	defer C.free(unsafe.Pointer(cstr))
 
 	runtime.LockOSThread()
 	defer runtime.UnlockOSThread()
 
-	ret := C.git_odb_write(oid.toC(), v.ptr, unsafe.Pointer(hdr.Data), C.size_t(hdr.Len), C.git_otype(otype))
+	ret := C.git_odb_write(oid.toC(), v.ptr, unsafe.Pointer(cstr), C.size_t(len(data)), C.git_otype(otype))
 
 	if ret < 0 {
 		return nil, MakeGitError(ret)