我在使用PortSIPSDK的演示中遇到了同样的错误，问题是配置中的问题。http://www.portsip.cn/docs/html_man/ios/html/index.html
1.将“-ObjC”添加到“构建设置”-〉“其他链接器标志”

UIDevice通常没有deviceType成员，PortSIP SDK中应该有扩展，你应该检查源代码，可能它们并不涵盖所有情况，但是你可以使用下面的代码来检测你的设备类型。

#include <sys/sysctl.h>
#include <sys/utsname.h>

- (NSString *) platformString{

NSLog(@"[UIDevice currentDevice].model: %@",[UIDevice currentDevice].model);
NSLog(@"[UIDevice currentDevice].description: %@",[UIDevice currentDevice].description);
NSLog(@"[UIDevice currentDevice].localizedModel: %@",[UIDevice currentDevice].localizedModel);
NSLog(@"[UIDevice currentDevice].name: %@",[UIDevice currentDevice].name);
NSLog(@"[UIDevice currentDevice].systemVersion: %@",[UIDevice currentDevice].systemVersion);
NSLog(@"[UIDevice currentDevice].systemName: %@",[UIDevice currentDevice].systemName);
NSLog(@"[UIDevice currentDevice].batteryLevel: %f",[UIDevice currentDevice].batteryLevel);      
struct utsname systemInfo;
uname(&systemInfo);
NSLog(@"[NSString stringWithCString:systemInfo.machine encoding:NSUTF8StringEncoding]: %@",[NSString stringWithCString:systemInfo.machine encoding:NSUTF8StringEncoding]);
NSString *platform = [NSString stringWithCString:systemInfo.machine encoding:NSUTF8StringEncoding];

    if ([platform isEqualToString:@"iPhone1,1"])    return @"iPhone 1G";
if ([platform isEqualToString:@"iPhone1,2"])    return @"iPhone 3G";
if ([platform isEqualToString:@"iPhone2,1"])    return @"iPhone 3GS";
if ([platform isEqualToString:@"iPhone3,1"])    return @"iPhone 4";
if ([platform isEqualToString:@"iPhone3,2"])    return @"iPhone 4 CDMA";
if ([platform isEqualToString:@"iPhone3,3"])    return @"Verizon iPhone 4";
if ([platform isEqualToString:@"iPhone4,1"])    return @"iPhone 4S";
if ([platform isEqualToString:@"iPhone5,1"])    return @"iPhone 5 (GSM)";
if ([platform isEqualToString:@"iPhone5,2"])    return @"iPhone 5 (GSM+CDMA)";
if ([platform isEqualToString:@"iPhone5,3"])    return @"iPhone 5c (GSM)";
if ([platform isEqualToString:@"iPhone5,4"])    return @"iPhone 5c (GSM+CDMA)";
if ([platform isEqualToString:@"iPhone6,1"])    return @"iPhone 5s (GSM)";
if ([platform isEqualToString:@"iPhone6,2"])    return @"iPhone 5s (GSM+CDMA)";
if ([platform isEqualToString:@"iPhone7,2"])    return @"iPhone 6";
if ([platform isEqualToString:@"iPhone7,1"])    return @"iPhone 6 Plus";
if ([platform isEqualToString:@"iPod1,1"])      return @"iPod Touch 1G";
if ([platform isEqualToString:@"iPod2,1"])      return @"iPod Touch 2G";
if ([platform isEqualToString:@"iPod3,1"])      return @"iPod Touch 3G";
if ([platform isEqualToString:@"iPod4,1"])      return @"iPod Touch 4G";
if ([platform isEqualToString:@"iPod5,1"])      return @"iPod Touch 5G";
if ([platform isEqualToString:@"iPad1,1"])      return @"iPad";
if ([platform isEqualToString:@"iPad2,1"])      return @"iPad 2 (WiFi)";
if ([platform isEqualToString:@"iPad2,2"])      return @"iPad 2 (Cellular)";
if ([platform isEqualToString:@"iPad2,3"])      return @"iPad 2 (Cellular)";
if ([platform isEqualToString:@"iPad2,4"])      return @"iPad 2 (WiFi)";
if ([platform isEqualToString:@"iPad2,5"])      return @"iPad Mini (WiFi)";
if ([platform isEqualToString:@"iPad2,6"])      return @"iPad Mini (Cellular)";
if ([platform isEqualToString:@"iPad2,7"])      return @"iPad Mini (Cellular)";
if ([platform isEqualToString:@"iPad3,1"])      return @"iPad 3 (WiFi)";
if ([platform isEqualToString:@"iPad3,2"])      return @"iPad 3 (Cellular)";
if ([platform isEqualToString:@"iPad3,3"])      return @"iPad 3 (Cellular)";
if ([platform isEqualToString:@"iPad3,4"])      return @"iPad 4 (WiFi)";
if ([platform isEqualToString:@"iPad3,5"])      return @"iPad 4 (Cellular)";
if ([platform isEqualToString:@"iPad3,6"])      return @"iPad 4 (Cellular)";
if ([platform isEqualToString:@"iPad4,1"])      return @"iPad Air (WiFi)";
if ([platform isEqualToString:@"iPad4,2"])      return @"iPad Air (Cellular)";
if ([platform isEqualToString:@"i386"])         return @"Simulator";
if ([platform isEqualToString:@"x86_64"])       return @"Simulator";
return @"Unknown";
}

我的问题与Bruno posted完全相同，因为我的目标是基于Swift Package的C++库，在Package.swift中添加以下linkerSettings解决了这个问题

linkerSettings: [
    .unsafeFlags([
        "-ObjC"
    ]),
]

我的第一次尝试是在cSettings中添加.define("OTHER_LDFLAGS",to: "-ObjC")，但这并没有解决问题，这可能是因为我也在使用cxxSettings，虽然不确定。