Using the LD LIBRARY PATH to load local libraries does not work on Linux

[sunliusi]

I need to use the local library for cross-platform. Local libraries have different implementations and Put them in different folders.

it work fine in windows just like this:
Environment.SetEnvironmentVariable("PATH", path + ";" + Environment.GetEnvironmentVariable("PATH"));

it's not working in linux just like this:
Environment.SetEnvironmentVariable("LD_LIBRARY_PATH", dir + ":" + Environment.GetEnvironmentVariable("LD_LIBRARY_PATH"));

[sunliusi]

NativeLibrary doesn't work either. There are two local libraries, one dependent on the other. This works only if the local library has no dependencies.

var path1 = Path.Combine(assemblyDirectory, "unix", "testaa.so");
               var p1 = NativeLibrary.Load(path1);
               if (p1 == IntPtr.Zero)
               {
                   throw new ApplicationException("load assembly fail:" + path1);
               }


               var path = Path.Combine(assemblyDirectory, "unix", "test.so");
               var p = NativeLibrary.Load(path);
               if (p == IntPtr.Zero)
               {
                   throw new ApplicationException("load assembly fail:" + path);
               }

---> System.DllNotFoundException: Unable to load shared library 'test.so' or one of its dependencies. In order to help diagnose loading problems, consider setting the LD_DEBUG environment variable: ./testaa.so: cannot open shared object file: No such file or directory
at System.Runtime.InteropServices.NativeLibrary.LoadFromPath(String libraryName, Boolean throwOnError)
at System.Runtime.InteropServices.NativeLibrary.Load(String libraryPath)

[DeafMan1983]

Hello,
I will tell you example with NativeLibrary()

      /*
        *  Valid library name for Linux of X11, Extensions, OpenGL and Vulkan
        */
       private const string libX11 = "libX11.so.6";
       private const string libXrender = "libXrender.so.0";
       private static IntPtr handle;

       static XLib()
       {
           // Important instance of TryGetExport()
           handle = NativeLibrary.Load(libX11, typeof(XLib).Assembly, 0);
       }

       /*
        *  Display *XOpenDisplay(char *displayname);
        */
       [UnmanagedFunctionPointer(CallingConvention.Cdecl)]
       private delegate IntPtr _XOpenDisplay(string displayname);
       public static Display XOpenDisplay(string displayname)
       {
           _XOpenDisplay opendisplay_delegate;
           if (NativeLibrary.TryGetExport(handle, "XOpenDisplay", out IntPtr opendisplay))
           {
               opendisplay_delegate = Marshal.GetDelegateForFunctionPointer<_XOpenDisplay>(opendisplay);
           }
           else
           {
               opendisplay_delegate = (string name) => { throw new NotImplementedException("Error: XOpenDisplay not found."); };
           }

           return new Display(opendisplay_delegate(displayname));
       }

If you want FullPath like this.
You should use "AppDomain.CurrentDomain.BaseDirectory"
like this:

            ...
            string rootdir = AppDomain.CurrentDomain.BaseDirectory;
            handle = NativeLibrary.Load(Path.Combine(rootdir, "unix", "sofile.so"), typeof(YourClass).Assembly, 0);
            ...

You should create delegate with UnmanagedFunctionPointer

        [UnmanagedFunctionPointer(CallingConvention.Cdecl)]
        private delegate void _Method(string sayhello);

Than you can try as public method if you try out.

        public static void Method(string sayhello)
        {
            _Method method_delegate;
            if (NativeLibrary.TryGetExport(handle, "Method", out IntPtr method_ptr))
            {
                method_delegate = Marshal.GetDelegateForFunctionPointer<_Method>(method_ptr);
            }
            else
            {
                method_delegate = (string name) => { throw new NotImplementedException("Error: Method not found."); };
            }

            method_delegate(sayhello);
        }

Just it is small example of my made.
I hope my solution helps you as well.

// EDIT: You mean multiple so files?
No problem for me

            ...
            // multiple so files
            string[] sofiles =
            {
                "file1.so", "file2.so"
            };
            string rootdir = AppDomain.CurrentDomain.BaseDirectory;
            foreach (string sofile in sofiles)
            {
                handle = NativeLibrary.Load(Path.Combine(rootdir, "unix", sofile));
            }
            ...

It is example:
For old version of NetFX 4.5 picture.

It is very easy to understand like I made it.

It is simple for you. I hope that.

[sunliusi]

Thanks @SourceSkyBoxer for such a detailed explanation.

Follow the example above:
// multiple so files string[] sofiles = { "file1.so", "file2.so" }; string rootdir = AppDomain.CurrentDomain.BaseDirectory; foreach (string sofile in sofiles) { handle = NativeLibrary.Load(Path.Combine(rootdir, "unix", sofile)); }

The problem is that NativeLibrary.Load will fail when file2.so references file1.so.

If you put file2.so and file1.so in the root directory, there is no problem

[sunliusi]

System.DllNotFoundException: Unable to load shared library '.../unix/file2.so' or one of its dependencies. In order to help diagnose loading problems, consider setting the LD_DEBUG environment variable: ./file1.so: cannot open shared object file: No such file or directory

[wli3]

This issue was moved to dotnet/runtime#34711