objective c gets EXC_BAD_ACCESS error on completionhandler - objective-c

Question

i'm new to objective-c, please bear with me if i ask stupid questions :)
The following is part of code i have to start vpn tunnel, but keeps getting EXC_BAD_ACCESS error
- (void)startTunnelWithOptions:(NSDictionary *)options completionHandler:(void (^)(BOOL * error))completionHandler {
vpnAdapter = [[OpenAdapter alloc] init];
vpnAdapter.delegate = self;
// get config
config = [[NSDictionary alloc] init];
NETunnelProviderProtocol *protocol = (NETunnelProviderProtocol *)self.protocolConfiguration;
config = protocol.providerConfiguration;
host = config[#"server"];
// Load config data
username = config[#"username"];
password = config[#"password"];
if(option != nil){
[vpnAdapter connect:host user:username pass:password add:YES completionHandler:^(BOOL success){
// return success;
completionHandler(&success); // Thread 2: EXC_BAD_ACCESS (code=1, address=0xbcc68f020)
}];
}else{
[vpnAdapter connect:host user:username pass:password add:NO completionHandler:^(BOOL success){
completionHandler(&success);
}];
}
}
here is connect method
- (void)connect: (NSString *) host user:(NSString *)username pass:(NSString *) password add:(Boolean) isAdd completionHandler:(void (^)(BOOL success)) completionHandler{
dispatch_queue_attr_t attributes = dispatch_queue_attr_make_with_qos_class(DISPATCH_QUEUE_SERIAL, QOS_CLASS_UTILITY, 0);
dispatch_queue_t connectQueue = dispatch_queue_create("me.ss-abramchuk.open-adapter.connection", attributes);
dispatch_async(connectQueue, ^{
// Call connect
//int ret=1;
NSArray* options = [NSArray arrayWithObjects:
#"--user", username,
host,
nil];
if(isAdd){
options = [NSArray arrayWithObjects:
#"--user", username,
#"--protocol", #"ad",
host,
nil];
}
//NSArray *paths = NSSearchPathForDirectoriesInDomains
(NSDocumentDirectory, NSUserDomainMask, YES);
//NSString *documentsDirectory = [paths objectAtIndex:0];
NSMutableArray *arguments = [NSMutableArray arrayWithCapacity:1+[options count]];
[arguments addObject:#"connect"];
[arguments addObjectsFromArray:options];
int argc = [arguments count];
char **argv = (char **)malloc(sizeof(char*) * (argc + 1));
[arguments enumerateObjectsUsingBlock:^(NSString *option, NSUInteger i, BOOL *stop) {
const char * c_string = [option UTF8String];
int length = (int)strlen(c_string);
char *c_string_copy = (char *) malloc(sizeof(char) * (length + 1));
strcpy(c_string_copy, c_string);
argv[i] = c_string_copy;
}];
argv[argc] = NULL;
const char *cfPass=[password UTF8String];
int ret = self.vpnClient->start2connect(argc, argv, cfPass);
BOOL result;
if (ret!=0){
result=false;
}
else {result = true;}
completionHandler(result);
});
}
all of these are from networkextension and while debugging, i found int ret = self.vpnClient->start2connect(argc, argv, cfPass);
seems not returning any value.
however, i confirmed that the start2connect method does return int value
so for now, anyone can help explain what's wrong?
thanks

Answer 1

The BOOL * is a pointer to a BOOL. We don’t use that pattern very often. We use it where the block needs to update a BOOL property somewhere, e.g. in enumerateMatchesinString, where you can update the boolean that stop points to in order to stop the enumeration.
But this is a completion handler, so there’s no point in passing a pointer to the boolean (one that presumably was on the stack, inviting problems). Just pass the boolean itself, not a pointer to it.
I would suggest that instead of:
- (void)startTunnelWithOptions:(NSDictionary *)options completionHandler:(void (^)(BOOL * error))completionHandler {
...
[vpnAdapter connect:host user:username pass:password add:YES completionHandler:^(BOOL success){
completionHandler(&success);
}];
...
}
That you want:
- (void)startTunnelWithOptions:(NSDictionary *)options completionHandler:(void (^)(BOOL success))completionHandler {
...
[vpnAdapter connect:host user:username pass:password add:YES completionHandler:^(BOOL success){
completionHandler(success);
}];
...
}
Note the block parameter isn’t BOOL * error but rather BOOL success and when it calls the completionHandler, there’s not & before success.
If there’s some reason you needed to update the BOOL, then that’s a different matter, but it doesn’t make sense in the context of a completion handler.