From 3c1ba8c40e4d654bfca8b535c861a63c41b16f27 Mon Sep 17 00:00:00 2001
From: Itamar Turner-Trauring <itamar@itamarst.org>
Date: Sat, 27 Aug 2016 20:44:46 +0200
Subject: [PATCH 1/4] Add test for slice-to-slice and GCo pointer detection

---
 .travis.yml  |  1 +
 blob_test.go | 26 ++++++++++++++++++++++++++
 2 files changed, 27 insertions(+)

diff --git a/.travis.yml b/.travis.yml
index f796389..016cf2d 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -10,6 +10,7 @@ go:
   - 1.3
   - 1.4
   - 1.5
+  - 1.6
   - tip
 
 matrix:
diff --git a/blob_test.go b/blob_test.go
index 2b5ec4f..652c50c 100644
--- a/blob_test.go
+++ b/blob_test.go
@@ -1,9 +1,21 @@
 package git
 
 import (
+	"bytes"
 	"testing"
 )
 
+type bufWrapper struct {
+	buf     [64]byte
+	pointer []byte
+}
+
+func doublePointerBytes() []byte {
+	o := &bufWrapper{}
+	o.pointer = o.buf[0:10]
+	return o.pointer[0:1]
+}
+
 func TestCreateBlobFromBuffer(t *testing.T) {
 	repo := createTestRepo(t)
 	defer cleanupTestRepo(t, repo)
@@ -14,4 +26,18 @@ func TestCreateBlobFromBuffer(t *testing.T) {
 	if id.String() != "e69de29bb2d1d6434b8b29ae775ad8c2e48c5391" {
 		t.Fatal("Empty buffer did not deliver empty blob id")
 	}
+
+	for _, data := range []([]byte){[]byte("hello there"), doublePointerBytes()} {
+		expected := make([]byte, len(data))
+		copy(expected, data)
+		id, err = repo.CreateBlobFromBuffer(data)
+		checkFatal(t, err)
+
+		blob, err := repo.LookupBlob(id)
+		checkFatal(t, err)
+		if !bytes.Equal(blob.Contents(), expected) {
+			t.Fatal("Loaded bytes don't match original bytes:",
+				blob.Contents(), "!=", expected)
+		}
+	}
 }

From b5d213c2c1229ea5de524ee24a9d9635a9cf303f Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Carlos=20Mart=C3=ADn=20Nieto?= <cmn@dwim.me>
Date: Sat, 27 Aug 2016 20:47:41 +0200
Subject: [PATCH 2/4] Remove unecessary copy

---
 blob_test.go | 6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/blob_test.go b/blob_test.go
index 652c50c..6b7cd49 100644
--- a/blob_test.go
+++ b/blob_test.go
@@ -28,16 +28,14 @@ func TestCreateBlobFromBuffer(t *testing.T) {
 	}
 
 	for _, data := range []([]byte){[]byte("hello there"), doublePointerBytes()} {
-		expected := make([]byte, len(data))
-		copy(expected, data)
 		id, err = repo.CreateBlobFromBuffer(data)
 		checkFatal(t, err)
 
 		blob, err := repo.LookupBlob(id)
 		checkFatal(t, err)
-		if !bytes.Equal(blob.Contents(), expected) {
+		if !bytes.Equal(blob.Contents(), data) {
 			t.Fatal("Loaded bytes don't match original bytes:",
-				blob.Contents(), "!=", expected)
+				blob.Contents(), "!=", data)
 		}
 	}
 }

From b41e4c4ac7c7ec4d45ec5d8903077bd01264549f Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Carlos=20Mart=C3=ADn=20Nieto?= <cmn@dwim.me>
Date: Sat, 27 Aug 2016 20:51:13 +0200
Subject: [PATCH 3/4] Work around Go 1.6's CGo pointer check

It depends heavily on the expression at the call site an whether it can
figure out whether we're using a slice or not, so provid an incantation
that does this.
---
 blob.go | 17 +++++++++++++----
 1 file changed, 13 insertions(+), 4 deletions(-)

diff --git a/blob.go b/blob.go
index 1a86e60..8b3e94f 100644
--- a/blob.go
+++ b/blob.go
@@ -37,15 +37,24 @@ func (repo *Repository) CreateBlobFromBuffer(data []byte) (*Oid, error) {
 	defer runtime.UnlockOSThread()
 
 	var id C.git_oid
-	var ptr unsafe.Pointer
+	var size C.size_t
 
+	// Go 1.6 added some increased checking of passing pointer to
+	// C, but its check depends on its expectations of waht we
+	// pass to the C function, so unless we take the address of
+	// its contents at the call site itself, it can fail when
+	// 'data' is a slice of a slice.
+	//
+	// When we're given an empty slice, create a dummy one where 0
+	// isn't out of bounds.
 	if len(data) > 0 {
-		ptr = unsafe.Pointer(&data[0])
+		size = C.size_t(len(data))
 	} else {
-		ptr = unsafe.Pointer(nil)
+		data = []byte{0}
+		size = C.size_t(0)
 	}
 
-	ecode := C.git_blob_create_frombuffer(&id, repo.ptr, ptr, C.size_t(len(data)))
+	ecode := C.git_blob_create_frombuffer(&id, repo.ptr, unsafe.Pointer(&data[0]), size)
 	if ecode < 0 {
 		return nil, MakeGitError(ecode)
 	}

From 5c678353faa4f180ee4ad8a5e58ca71e093cf757 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Carlos=20Mart=C3=ADn=20Nieto?= <cmn@dwim.me>
Date: Sat, 27 Aug 2016 20:52:07 +0200
Subject: [PATCH 4/4] Add Go 1.7 to the build list

---
 .travis.yml | 1 +
 1 file changed, 1 insertion(+)

diff --git a/.travis.yml b/.travis.yml
index 016cf2d..79ad168 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -11,6 +11,7 @@ go:
   - 1.4
   - 1.5
   - 1.6
+  - 1.7
   - tip
 
 matrix: