Feature Request: malloc deallocate buffer in iOS SDK

[wonhee-jeong]

Checklist

• I've updated to the latest released version of the SDK
• I've searched for existing feature requests on GitHub issues
• I've read the Code of Conduct
• I've given my issue the title: Feature Request: [name of my feature request]

Goals

When returning a String from an iOS SDK function, it is returned as char*. The char* is a buffer allocated with malloc, but I can't find where to free it. Are there any memory leaks?
Isn't there a possibility of a memory leak in the iOS SDK functions?

Expected Results

Buffers allocated with malloc must be freed.

Code Samples & Details

facebook-sdk-for-unity/UnitySDK/Assets/FacebookSDK/SDK/Editor/iOS/FBUnityInterface.mm

Lines 438 to 459 in 9abd766

	char* IOSFBCurrentAuthenticationToken()
	{
	FBSDKAuthenticationToken *token = [FBSDKAuthenticationToken currentAuthenticationToken];
	NSString *str = @"";
	if (token.tokenString && token.nonce) {
	try {
	NSData *jsonData = [NSJSONSerialization dataWithJSONObject:@{
	@"auth_token_string": token.tokenString,
	@"auth_nonce": token.nonce
	} options:NSJSONWritingPrettyPrinted error:nil];
	if (jsonData) {
	str = [[NSString alloc] initWithData:jsonData encoding:NSUTF8StringEncoding];
	}
	} catch (NSException *exception) {
	NSLog(@"Fail to parse AuthenticationToken");
	}
	}
	const char* string = [str UTF8String];
	char* res = (char*)malloc(strlen(string) + 1);
	strcpy(res, string);
	return res;
	}

An example is the char* IOSFBCurrentAuthenticationToken(), char* IOSFBCurrentProfile(),char* IOSFBSdkVersion().. function.