iOS C++11 linking issue under Xcode?

Development Platform & Builds Mobile
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In the TopDown example project under Xcode, it seems that C++11 library usage (e.g. std::string) can be compiled properly under the iOS → iPhone 5s scheme, but the linking failed with the following error, is there a missing “-lc++” linker flag that needs to be set in IOSToolChain.cs?

Setting up Mono
Building TopDown…
Compiling with iPhoneOS SDK 9.1
Parsing headers for TopDown
Running UnrealHeaderTool “/Users/me/Projects/UE4/TopDown/TopDown.uproject” “/Users/me/Projects/UE4/TopDown/Intermediate/Build/IOS/TopDown/DebugGame/UnrealHeaderTool.manifest” -LogCmds=“loginit warning, logexit warning, logdatabase error” -rocket -installed
Reflection code generated for TopDown in 6.8821027 seconds
Compiling with these architectures: armv7
Performing 2 actions (8 in parallel)
[1/2] clang++ TopDownGameMode.cpp
[2/2] clang++ /Users/me/Projects/UE4/TopDown/Binaries/IOS/TopDown-IOS-DebugGame
Undefined symbols for architecture armv7:
“std::__1::basic_string, std::__1::allocator >::append(char const*)”, referenced from:
ATopDownGameMode::ATopDownGameMode() in TopDownGameMode.cpp.o
“std::__1::basic_string, std::__1::allocator >::~basic_string()”, referenced from:
ATopDownGameMode::ATopDownGameMode() in TopDownGameMode.cpp.o
ld: symbol(s) not found for architecture armv7
clang: error: linker command failed with exit code 1 (use -v to see invocation)
-------- End Detailed Actions Stats -----------------------------------------------------------
ERROR: UBT ERROR: Failed to produce item: /Users/me/Projects/UE4/TopDown/Binaries/IOS/TopDown-IOS-DebugGame
Total build time: 20.48 seconds
Command /Users/Shared/UnrealEngine/4.9/Engine/Build/BatchFiles/Mac/RocketBuild.sh failed with exit code 5

2

// Copyright 1998-2015 Epic Games, Inc. All Rights Reserved.

#include "TopDown.h"
#include "TopDownGameMode.h"
#include "TopDownPlayerController.h"
#include "TopDownCharacter.h"

#include <string>

ATopDownGameMode::ATopDownGameMode()
{
	// use our custom PlayerController class
	PlayerControllerClass = ATopDownPlayerController::StaticClass();

	// set default pawn class to our Blueprinted character
	static ConstructorHelpers::FClassFinder<APawn> PlayerPawnBPClass(TEXT("/Game/TopDownCPP/Blueprints/TopDownCharacter"));
	if (PlayerPawnBPClass.Class != NULL)
	{
		DefaultPawnClass = PlayerPawnBPClass.Class;
	}
    
    std::string s;
    s += "hello";
}
3

This seems to be resolved in engine version 4.10.1. All the c++11 dependencies are able to be compiled and linked correctly, everything runs like a charm!