Stop passing Go pointers to C

.travis.yml

@@ -2,6 +2,7 @@ language: go
 
 go:
   - 1.4
+  - 1.5
   - tip
 
 before_install:

callback.go

@@ -0,0 +1,30 @@
+package pam
+
+import "sync"
+
+var cb struct {
+	sync.Mutex
+	m map[int]interface{}
+	c int
+}
+
+func cbAdd(v interface{}) int {
+	cb.Lock()
+	defer cb.Unlock()
+	if cb.m == nil {
+		cb.m = make(map[int]interface{})
+	}
+	cb.c++
+	cb.m[cb.c] = v
+	return cb.c
+}
+
+func cbGet(c int) interface{} {
+	cb.Lock()
+	defer cb.Unlock()
+	v := cb.m[c]
+	if v == nil {
+		panic("Callback pointer not found")
+	}
+	return v
+}

callback_test.go

@@ -0,0 +1,23 @@
+package pam
+
+import (
+	"reflect"
+	"testing"
+)
+
+func TestCallback_001(t *testing.T) {
+	c := cbAdd(TestCallback_001)
+	v := cbGet(c)
+	if reflect.TypeOf(v) != reflect.TypeOf(TestCallback_001) {
+		t.Error("Received unexpected value")
+	}
+}
+
+func TestCallback_002(t *testing.T) {
+	defer func() {
+		recover()
+	}()
+	c := cbAdd(TestCallback_002)
+	cbGet(c + 1)
+	t.Error("Expected a panic")
+}

transaction.c

@@ -19,7 +19,7 @@ int cb_pam_conv(
 		struct cbPAMConv_return result = cbPAMConv(
 				msg[i]->msg_style,
 				(char *)msg[i]->msg,
-				appdata_ptr);
+				(long)appdata_ptr);
 		if (result.r1 != PAM_SUCCESS) {
 			goto error;
 		}
@@ -39,13 +39,8 @@ error:
 	return PAM_CONV_ERR;
 }
 
-struct pam_conv *make_pam_conv(void *appdata_ptr)
+void init_pam_conv(struct pam_conv *conv, long c)
 {
-	struct pam_conv* conv = malloc(sizeof *conv);
-	if (!conv) {
-		return NULL;
-	}
 	conv->conv = cb_pam_conv;
-	conv->appdata_ptr = appdata_ptr;
-	return conv;
+	conv->appdata_ptr = (void *)c;
 }

transaction.go

@@ -4,7 +4,7 @@ package pam
 //#include <stdlib.h>
 //#cgo CFLAGS: -Wall -std=c99
 //#cgo LDFLAGS: -lpam
-//struct pam_conv *make_pam_conv(void *);
+//void init_pam_conv(struct pam_conv *conv, long c);
 import "C"
 
 import (
@@ -50,31 +50,31 @@ func (f ConversationFunc) RespondPAM(s Style, msg string) (string, error) {
 	return f(s, msg)
 }
 
-// Internal conversation structure
-type conversation struct {
-	handler ConversationHandler
-	conv    *C.struct_pam_conv
-}
-
 // Constructs a new conversation object with a given handler and a newly
 // allocated pam_conv struct that uses this object as its appdata_ptr.
-func newConversation(handler ConversationHandler) (*conversation, C.int) {
-	c := &conversation{}
-	c.handler = handler
-	c.conv = C.make_pam_conv(unsafe.Pointer(c))
-	if c.conv == nil {
-		return nil, C.PAM_BUF_ERR
-	}
-	return c, C.PAM_SUCCESS
+func newConversation(handler ConversationHandler) (*C.struct_pam_conv, C.int) {
+	c := cbAdd(handler)
+	conv := &C.struct_pam_conv{}
+	C.init_pam_conv(conv, C.long(c))
+	return conv, C.PAM_SUCCESS
 }
 
 // Go-side function for processing a single conversational message. Ultimately
 // this calls the associated ConversationHandler's ResponsePAM callback with data
 // coming in from a C-side call.
 //export cbPAMConv
-func cbPAMConv(s C.int, msg *C.char, appdata unsafe.Pointer) (*C.char, C.int) {
-	c := (*conversation)(appdata)
-	r, err := c.handler.RespondPAM(Style(s), C.GoString(msg))
+func cbPAMConv(s C.int, msg *C.char, c int) (*C.char, C.int) {
+	var r string
+	var err error
+	v := cbGet(c)
+	switch cb := v.(type) {
+	case ConversationFunc:
+		r, err = cb(Style(s), C.GoString(msg))
+	case ConversationHandler:
+		r, err = cb.RespondPAM(Style(s), C.GoString(msg))
+	default:
+		return nil, C.PAM_CONV_ERR
+	}
 	if err != nil {
 		return nil, C.PAM_CONV_ERR
 	}
@@ -84,14 +84,13 @@ func cbPAMConv(s C.int, msg *C.char, appdata unsafe.Pointer) (*C.char, C.int) {
 // Transaction is the application's handle for a PAM transaction.
 type Transaction struct {
 	handle *C.pam_handle_t
-	conv   *conversation
+	conv   *C.struct_pam_conv
 	status C.int
 }
 
 // Finalize a PAM transaction.
 func transactionFinalizer(t *Transaction) {
 	C.pam_end(t.handle, t.status)
-	C.free(unsafe.Pointer(t.conv.conv))
 }
 
 // Start initiates a new PAM transaction. Service is treated identically to
@@ -112,9 +111,8 @@ func Start(service, user string, handler ConversationHandler) (*Transaction, err
 		u = C.CString(user)
 		defer C.free(unsafe.Pointer(u))
 	}
-	t.status = C.pam_start(s, u, t.conv.conv, &t.handle)
+	t.status = C.pam_start(s, u, t.conv, &t.handle)
 	if t.status != C.PAM_SUCCESS {
-		C.free(unsafe.Pointer(t.conv.conv))
 		return nil, t
 	}
 	runtime.SetFinalizer(t, transactionFinalizer)