ThirdParty undefined symbol linking failure for Linux

Development Platform & Builds
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1

Using the cross-compile option on Windows, I am attempting to build a plugin that uses a ThirdParty .so. I used the template to create the plugin from the editor. In MyPlugin.Build.cs I have added in a dependency for MWLibrary:

	PublicDependencyModuleNames.AddRange(
		new string[] {
			"Core",
			"RenderCore",
			"ShaderCore",
			"RHI",
			"Landscape",
			"MWLibrary",
                             "Projects"
			// ... add other public dependencies that you statically link with here ...
		}
		);

Then MWLibrary.Build.cs is this:

using System.IO;
using UnrealBuildTool;
using System.Diagnostics;
using System.Collections.Generic;

public class MWLibrary : ModuleRules
{
	public MWLibrary(ReadOnlyTargetRules Target) : base(Target)
	{
		Type = ModuleType.External;
        if (Target.Platform == UnrealTargetPlatform.Win64 || Target.Platform == UnrealTargetPlatform.Win32 ||
            Target.Platform == UnrealTargetPlatform.Mac || Target.Platform == UnrealTargetPlatform.Linux)
        {
            bool bDebug = (Target.Configuration == UnrealTargetConfiguration.Debug && Target.bDebugBuildsActuallyUseDebugCRT);

            string LibDir = Path.Combine(ModuleDirectory, "LiveIODeploy");
            string Platform;
            string LibExtension;
            switch (Target.Platform)
            {
                case UnrealTargetPlatform.Win64:
                    Platform = "win64";
                    LibExtension = bDebug ? ".d.lib" : ".lib";
                    break;
                case UnrealTargetPlatform.Mac:
                    Platform = "maci64";
                    LibExtension = ".dylib";
                    break;
                case UnrealTargetPlatform.Linux:
                    Platform = "glnxa64";
                    LibExtension = bDebug ? ".so.dbg" : ".so";
                    break;
                default:
                    return;
            }
            LibDir = Path.Combine(LibDir, Platform);
            PublicLibraryPaths.Add(LibDir);
            PublicIncludePaths.Add(Path.Combine(ModuleDirectory, "LiveIODeploy", "include"));

            List<string> ReqLibraryNames = new List<string>();
            if (Target.Platform == UnrealTargetPlatform.Win64)
            {
                ReqLibraryNames.AddRange
                (
                    new string[] {
                    "mwlive_core",
                    "mwlive_utils"
                });
            }
            else if (Target.Platform == UnrealTargetPlatform.Mac)
            {
                ReqLibraryNames.AddRange
                (
                    new string[] {
                    "libmwlive_core",
                    "libmwlive_utils"
                  });
			}
            else if (Target.Platform == UnrealTargetPlatform.Linux)
            {                
                ReqLibraryNames.AddRange
                (
                    new string[] {
                    "libmwlive_core",
                    "libmwlive_utils"
                  });
            }

            foreach (string LibraryName in ReqLibraryNames)
            {
                string LibName = Path.Combine(LibDir, LibraryName + LibExtension);
                PublicAdditionalLibraries.Add(LibName);
                PublicDelayLoadDLLs.Add(LibraryName + LibExtension);
                RuntimeDependencies.Add(LibName);
                
            }
        }
	}
}

When linking I see the following:

2>C:\UnrealToolchains\v11_clang-5.0.0-centos7\x86_64-unknown-linux-gnu\bin\ld.lld.exe : error : undefined symbol: live::core::PublisherSharedMemory::getParticipantPublisherSharedMemory(std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> >, unsigned long)
2>>>> referenced by SdCamera.cpp:36 (J:\VrtlEnv\Plugins\MWSimulation\Source\MWSimulation\Private\SdCamera.cpp:36)
2>>>>               Module.MWSimulation.cpp.o:(ASdCamera::CreateSettingsTopicReader()) in archive J:/VrtlEnv/Plugins/MWSimulation/Binaries/Linux/libUE4-MWSimulation.a
2>clang++.exe : error : linker command failed with exit code 1 (use -v to see invocation)
2>UnrealBuildTool : error : UBT ERROR: Failed to produce item: J:\VrtlEnv\Binaries\Linux\VrtlEnv

Have I missed something or did it incorrectly? Thanks!

1 Like
2

The library needed C++11, libc++ not libstdc++, and the correct version of clang
So in my CMakeLists:

set(CMAKE_CXX_STANDARD 11)
set(CMAKE_CXX_FLAGS "-std=c++11 -stdlib=libc++")
set(CMAKE_EXE_LINKER_FLAGS "-stdlib=libc++ -lc++abi")

and then $cmake … -DCMAKE_C_COMPILER=clang-5.0 -DCMAKE_CXX_COMPILER=clang+±5.0