fix: release what calls from Go autorelease

.github/workflows/build.yml

@@ -20,3 +20,7 @@ jobs:
 
       - name: vet
         run: go vet ./...
+
+      # The tests need no Bluetooth controller.
+      - name: test
+        run: go test ./...

att.go

@@ -48,24 +48,32 @@ type ATTRequest struct {
 
 // Central: https://developer.apple.com/documentation/corebluetooth/cbattrequest/1518995-central
 func (r ATTRequest) Central() Central {
+	defer popPool(pushPool())
+
 	ptr := C.cb_atr_central(r.ptr)
 	return Central{unsafe.Pointer(ptr)}
 }
 
 // Characteristic: https://developer.apple.com/documentation/corebluetooth/cbattrequest/1518716-characteristic
 func (r ATTRequest) Characteristic() Characteristic {
+	defer popPool(pushPool())
+
 	ptr := C.cb_atr_characteristic(r.ptr)
 	return Characteristic{unsafe.Pointer(ptr)}
 }
 
 // Value: https://developer.apple.com/documentation/corebluetooth/cbattrequest/1518795-value
 func (r ATTRequest) Value() []byte {
+	defer popPool(pushPool())
+
 	ba := C.cb_atr_value(r.ptr)
 	return byteArrToByteSlice(&ba)
 }
 
 // SetValue: https://developer.apple.com/documentation/corebluetooth/cbattrequest/1518795-value
 func (r ATTRequest) SetValue(v []byte) {
+	defer popPool(pushPool())
+
 	ba := byteSliceToByteArr(v)
 	defer C.free(unsafe.Pointer(ba.data))
 
@@ -74,5 +82,7 @@ func (r ATTRequest) SetValue(v []byte) {
 
 // Offset: https://developer.apple.com/documentation/corebluetooth/cbattrequest/1518857-offset
 func (r ATTRequest) Offset() int {
+	defer popPool(pushPool())
+
 	return int(C.cb_atr_offset(r.ptr))
 }

bt.h

@@ -79,6 +79,8 @@ struct pmgr_restore_opts {
 bool bt_start();
 void bt_stop();
 void bt_init();
+void *bt_pool_push();
+void bt_pool_pop(void *pool);
 
 // util.m
 struct byte_arr nsdata_to_byte_arr(const NSData *nsdata);

bt.m

@@ -58,3 +58,20 @@
     bt_dlg = [[BTDlg alloc] init];
     [bt_dlg retain];
 }
+
+/**
+ * Pushes an autorelease pool on the calling thread.  Go threads have none, so
+ * an object autoreleased by a call from Go stays allocated until bt_pool_pop
+ * drains the pool this returns.
+ */
+void *
+bt_pool_push()
+{
+    return [[NSAutoreleasePool alloc] init];
+}
+
+void
+bt_pool_pop(void *pool)
+{
+    [(NSAutoreleasePool *)pool drain];
+}

central.go

@@ -15,11 +15,15 @@ type Central struct {
 
 // Identifier: https://developer.apple.com/documentation/corebluetooth/cbpeer/1620687-identifier
 func (c Central) Identifier() UUID {
+	defer popPool(pushPool())
+
 	cstr := C.cb_peer_identifier(c.ptr)
 	return MustParseUUID(C.GoString(cstr))
 }
 
 // MaximumUpdateValueLength: https://developer.apple.com/documentation/corebluetooth/cbcentral/1408800-maximumupdatevaluelength
 func (c Central) MaximumUpdateValueLength() int {
+	defer popPool(pushPool())
+
 	return int(C.cb_cent_maximum_update_len(c.ptr))
 }

centralmanager.go

@@ -64,6 +64,8 @@ func findCentralManagerDlg(ptr unsafe.Pointer) CentralManagerDelegate {
 // NewCentralManager creates a central manager.  Specify a nil `opts` value for
 // defaults.  Don't forget to call `SetDelegate()` afterwards!
 func NewCentralManager(opts *ManagerOpts) CentralManager {
+	defer popPool(pushPool())
+
 	if opts == nil {
 		opts = &DfltManagerOpts
 	}
@@ -84,6 +86,8 @@ func NewCentralManager(opts *ManagerOpts) CentralManager {
 // SetDelegate configures a receiver for a central manager's asynchronous
 // callbacks.
 func (cm CentralManager) SetDelegate(d CentralManagerDelegate) {
+	defer popPool(pushPool())
+
 	if d != nil {
 		cmgrPtrMap.add(cm.ptr, d)
 	}
@@ -92,11 +96,15 @@ func (cm CentralManager) SetDelegate(d CentralManagerDelegate) {
 
 // State: https://developer.apple.com/documentation/corebluetooth/cbmanager/1648600-state
 func (cm CentralManager) State() ManagerState {
+	defer popPool(pushPool())
+
 	return ManagerState(C.cb_cmgr_state(cm.ptr))
 }
 
 // Connect: https://developer.apple.com/documentation/corebluetooth/cbcentralmanager/1518766-connectperipheral
 func (cm CentralManager) Connect(prph Peripheral, opts *CentralManagerConnectOpts) {
+	defer popPool(pushPool())
+
 	if opts == nil {
 		opts = &DfltCentralManagerConnectOpts
 	}
@@ -115,11 +123,15 @@ func (cm CentralManager) Connect(prph Peripheral, opts *CentralManagerConnectOpt
 
 // CancelConnect: https://developer.apple.com/documentation/corebluetooth/cbcentralmanager/1518952-cancelperipheralconnection
 func (cm CentralManager) CancelConnect(prph Peripheral) {
+	defer popPool(pushPool())
+
 	C.cb_cmgr_cancel_connect(cm.ptr, prph.ptr)
 }
 
 // RetrieveConnectedPeripheralsWithServices: https://developer.apple.com/documentation/corebluetooth/cbcentralmanager/1518924-retrieveconnectedperipheralswith
 func (cm CentralManager) RetrieveConnectedPeripheralsWithServices(uuids []UUID) []Peripheral {
+	defer popPool(pushPool())
+
 	strs := uuidsToStrArr(uuids)
 	defer freeStrArr(&strs)
 
@@ -138,6 +150,8 @@ func (cm CentralManager) RetrieveConnectedPeripheralsWithServices(uuids []UUID)
 
 // RetrievePeripheralsWithIdentifiers: https://developer.apple.com/documentation/corebluetooth/cbcentralmanager/1519127-retrieveperipheralswithidentifie
 func (cm CentralManager) RetrievePeripheralsWithIdentifiers(uuids []UUID) []Peripheral {
+	defer popPool(pushPool())
+
 	strs := uuidsToStrArr(uuids)
 	defer freeStrArr(&strs)
 
@@ -156,6 +170,8 @@ func (cm CentralManager) RetrievePeripheralsWithIdentifiers(uuids []UUID) []Peri
 
 // Scan: https://developer.apple.com/documentation/corebluetooth/cbcentralmanager/1518986-scanforperipheralswithservices
 func (cm CentralManager) Scan(serviceUUIDs []UUID, opts *CentralManagerScanOpts) {
+	defer popPool(pushPool())
+
 	arrSvcUUIDs := uuidsToStrArr(serviceUUIDs)
 	defer freeStrArr(&arrSvcUUIDs)
 
@@ -176,10 +192,14 @@ func (cm CentralManager) Scan(serviceUUIDs []UUID, opts *CentralManagerScanOpts)
 
 // StopScan: https://developer.apple.com/documentation/corebluetooth/cbcentralmanager/1518984-stopscan
 func (cm CentralManager) StopScan() {
+	defer popPool(pushPool())
+
 	C.cb_cmgr_stop_scan(cm.ptr)
 }
 
 // IsScanning: https://developer.apple.com/documentation/corebluetooth/cbcentralmanager/1620640-isscanning
 func (cm CentralManager) IsScanning() bool {
+	defer popPool(pushPool())
+
 	return bool(C.cb_cmgr_is_scanning(cm.ptr))
 }

characteristic.go

@@ -39,24 +39,32 @@ type Characteristic struct {
 
 // UUID: https://developer.apple.com/documentation/corebluetooth/cbattribute/1620638-uuid
 func (c Characteristic) UUID() UUID {
+	defer popPool(pushPool())
+
 	cstr := C.cb_chr_uuid(c.ptr)
 	return MustParseUUID(C.GoString(cstr))
 }
 
 // Service: https://developer.apple.com/documentation/corebluetooth/cbcharacteristic/1518728-service
 func (c Characteristic) Service() Service {
+	defer popPool(pushPool())
+
 	ptr := C.cb_chr_service(c.ptr)
 	return Service{ptr}
 }
 
 // Value: https://developer.apple.com/documentation/corebluetooth/cbcharacteristic/1518878-value
 func (c Characteristic) Value() []byte {
+	defer popPool(pushPool())
+
 	ba := C.cb_chr_value(c.ptr)
 	return byteArrToByteSlice(&ba)
 }
 
 // Descriptors: https://developer.apple.com/documentation/corebluetooth/cbcharacteristic/1518957-descriptors
 func (c Characteristic) Descriptors() []Descriptor {
+	defer popPool(pushPool())
+
 	oa := C.cb_chr_descriptors(c.ptr)
 	defer C.free(unsafe.Pointer(oa.objs))
 
@@ -71,10 +79,14 @@ func (c Characteristic) Descriptors() []Descriptor {
 
 // Properties: https://developer.apple.com/documentation/corebluetooth/cbcharacteristic/1519010-properties
 func (c Characteristic) Properties() CharacteristicProperties {
+	defer popPool(pushPool())
+
 	return CharacteristicProperties(C.cb_chr_properties(c.ptr))
 }
 
 // IsNotifying: https://developer.apple.com/documentation/corebluetooth/cbcharacteristic/1519057-isnotifying
 func (c Characteristic) IsNotifying() bool {
+	defer popPool(pushPool())
+
 	return bool(C.cb_chr_is_notifying(c.ptr))
 }

cmgr.m

@@ -57,7 +57,6 @@
              const struct scan_opts *opts)
 {
     NSArray *arr_svc_uuids = strs_to_cbuuids(svc_uuids);
-    [arr_svc_uuids autorelease];
 
     NSMutableDictionary *dict = [[NSMutableDictionary alloc] init];
     [dict autorelease];
@@ -69,7 +68,6 @@
 
     if (opts->sol_svc_uuids.count > 0) {
         NSArray *arr_sol_svc_uuids = strs_to_cbuuids(&opts->sol_svc_uuids);
-        [arr_sol_svc_uuids autorelease];
 
         [dict setObject:arr_sol_svc_uuids
                  forKey:CBCentralManagerScanOptionSolicitedServiceUUIDsKey];
@@ -150,8 +148,10 @@
     void **objs = malloc([prphs count] * sizeof *objs);
     assert(objs != NULL);
 
+    // Go keeps these after the pool releases the array, so each one is
+    // retained like a peripheral the delegate hands to Go.
     for (int i = 0; i < [prphs count]; i++) {
-        objs[i] = [prphs objectAtIndex:i];
+        objs[i] = [[prphs objectAtIndex:i] retain];
     }
 
     return (struct obj_arr) {
@@ -175,8 +175,10 @@
     void **objs = malloc([prphs count] * sizeof *objs);
     assert(objs != NULL);
 
+    // Go keeps these after the pool releases the array, so each one is
+    // retained like a peripheral the delegate hands to Go.
     for (int i = 0; i < [prphs count]; i++) {
-        objs[i] = [prphs objectAtIndex:i];
+        objs[i] = [[prphs objectAtIndex:i] retain];
     }
 
     return (struct obj_arr) {

cutil.go

@@ -9,9 +9,29 @@ package cbgo
 import "C"
 
 import (
+	"runtime"
 	"unsafe"
 )
 
+// pushPool pushes an autorelease pool for a call into Objective-C, and locks
+// the goroutine to its thread until popPool drains it: a pool belongs to the
+// thread that pushed it. Every function that calls into Objective-C starts
+// with
+//
+//	defer popPool(pushPool())
+//
+// so that what the call autoreleases is released when it returns, after the
+// function has copied any C string or bytes that point into those objects.
+func pushPool() unsafe.Pointer {
+	runtime.LockOSThread()
+	return C.bt_pool_push()
+}
+
+func popPool(pool unsafe.Pointer) {
+	C.bt_pool_pop(pool)
+	runtime.UnlockOSThread()
+}
+
 func mallocArr(numElems int, elemSize uintptr) unsafe.Pointer {
 	return C.malloc(C.size_t(numElems) * C.size_t(elemSize))
 }

descriptor.go

@@ -15,18 +15,24 @@ type Descriptor struct {
 
 // UUID: https://developer.apple.com/documentation/corebluetooth/cbattribute/1620638-uuid
 func (d Descriptor) UUID() UUID {
+	defer popPool(pushPool())
+
 	cstr := C.cb_dsc_uuid(d.ptr)
 	return MustParseUUID(C.GoString(cstr))
 }
 
 // Characteristic: https://developer.apple.com/documentation/corebluetooth/cbdescriptor/1519035-characteristic
 func (d Descriptor) Characteristic() Characteristic {
+	defer popPool(pushPool())
+
 	ptr := C.cb_dsc_characteristic(d.ptr)
 	return Characteristic{ptr}
 }
 
 // Value: https://developer.apple.com/documentation/corebluetooth/cbdescriptor/1518778-value
 func (d Descriptor) Value() []byte {
+	defer popPool(pushPool())
+
 	ba := C.cb_dsc_value(d.ptr)
 	return byteArrToByteSlice(&ba)
 }

internal/heap/heap.go

@@ -0,0 +1,21 @@
+// Package heap measures the C heap, for tests that check what a call into
+// Objective-C leaves allocated.
+package heap
+
+/*
+#include <malloc/malloc.h>
+
+static size_t
+heap_in_use(void)
+{
+    malloc_statistics_t stats;
+    malloc_zone_statistics(NULL, &stats);
+    return stats.size_in_use;
+}
+*/
+import "C"
+
+// InUse returns the bytes allocated in every malloc zone of the process.
+func InUse() int {
+	return int(C.heap_in_use())
+}