Recently I have been trying to get some Point Cloud Library functionality going in my .NET framework application, and considering that there is no completely functional wrapper for PCL for C#, I made my own for a few functions as a test. Something like this:
[DllImport(DllFilePath, CallingConvention = CallingConvention.Cdecl)]
public extern static IntPtr StatisticalOutlierFilter(IntPtr data, int length, int meanK = 50, float mulThresh = 1.0f);
Which calls a function from a C++ library, such as this:
EXPORT VectorXYZ* StatisticalOutlierFilter(VectorXYZ* data, int length, int meanK, float mulThresh) {
auto processedCloud = process.StatisticalOutlierFilter(data, length, meanK, mulThresh);
auto processedVector = convert.ToVectorXYZ(processedCloud);
return processedVector;
}
Where EXPORT is defined such for gcc:
#define EXPORT extern "C" __attribute__ ((visibility ("default")))
And relevant processing function from PCL is implemented such in a class (note that the returned is a boost shared pointer):
PointCloud<PointXYZ>::Ptr Processors::StatisticalOutlierFilter(VectorXYZ* data, int length, int meanK, float mulThresh) {
auto cloud = PrepareCloud(data, length);
PointCloud<PointXYZ>::Ptr cloud_filtered(new PointCloud<PointXYZ>);
StatisticalOutlierRemoval<PointXYZ> sor;
sor.setInputCloud(cloud);
sor.setMeanK(meanK);
sor.setStddevMulThresh(mulThresh);
sor.filter(*cloud_filtered);
return cloud_filtered;
}
This procedure works well with a dll built w/MSVC and running the whole thing on Windows, though the final target is gcc/Linux/Mono, where I get several errors of the following type (this is from mono debug):
'libavpcl_dll.so': '/usr/lib/libavpcl_dll.so: undefined symbol: _ZN3pcl7PCLBaseINS_8PointXYZEE13setInputCloudERKN5boost10shared_ptrIKNS_10PointCloudIS1_EEEE'.
I have investigated quite a bit so far, and have set my CmakeLists.txt to set(CMAKE_CXX_VISIBILITY_PRESET hidden) , therefore, I imagine, only functions I defined as EXPORT should be visible and imported - however, that is not the case, and I get the aforementioned errors. PCL was installed on Windows via vcpkg and on Xubuntu via apt. I am somewhat stumped as to what is the error source, considering the code runs well on windows, and builds without issue on Linux. Thanks.
I've been running into the same issue as you. I solved it by adding each reference library into the CMakeLists.txt file (I was missing the reference files which gave me the similar missing symbol issues).
I'm at the 'I don't know why this worked' stage but I can give you step by step implementation (I'm also trying to use DllImport into .NET on Linux).
Started with this:
https://medium.com/#xaviergeerinck/how-to-bind-c-code-with-dotnet-core-157a121c0aa6
Then added my in-scope files thanks to the main comment here: How to create a shared library with cmake?:
add_library(mylib SHARED
sources/animation.cpp
sources/buffers.cpp
[...]
)
run cmake .
run make -j$(grep -c ^processor /proc/cpuinfo)
copy path to .so file
DllImport path from above to my c# app
Related
I have a PoC to use some existing Java-codebase in some UWP-app using the most current Visual Studio Community 19 version 16.3.2 and the latest released IKVM 8.1.7195.0. The app builds and runs fine in Debug-mode, but fails to build already in Release-mode with the following error:
MCG0004:InternalAssert Assert Failed: ICE: trying to add a local var
with the same name, but different types. during
[_RegisterClipboardFormat] Ams.Oms.Poc
RegisterClipboardFormat is part of IKVM:
#DllImportAttribute.Annotation(value = "user32.dll", EntryPoint = "RegisterClipboardFormat")
private native static int _RegisterClipboardFormat(String format);
#cli.System.Security.SecuritySafeCriticalAttribute.Annotation
private static int RegisterClipboardFormat(String format)
{
return _RegisterClipboardFormat(format);
}
https://github.com/ikvm-revived/ikvm/blob/master/openjdk/sun/awt/IkvmDataTransferer.java#L95
What I'm wondering is which local variable the error message is referring to? Might be something added implicitly or might have to do with String in Java vs. string in C#? OTOH that file is clearly named .java.
Didn't find much about the error message in general, only the following two links seems to be more interesting:
Variables having same name but different type
Why doesn't C# allow me to use the same variable name in different scopes?
So I'm currently even unsure where the message comes from, Visual Studio/C# directly or IKVM during running code during building Release-mode. I strongly suspect the error is coming from Visual Studio/C#, though.
Searching for the function itself doesn't reveal much of help as well:
Sorry, AWT is not a supported part of IKVM.
https://sourceforge.net/p/ikvm/bugs/225/
Others seemed to have the same problem, because CN1 simply disabled that code entirely in their fork of IKVM:
//#DllImportAttribute.Annotation(value = "user32.dll", EntryPoint = "RegisterClipboardFormat")
//private native static int _RegisterClipboardFormat(String format);
#cli.System.Security.SecuritySafeCriticalAttribute.Annotation
private static int RegisterClipboardFormat(String format)
{
throw new Error("Not implemented");
//return _RegisterClipboardFormat(format);
}
https://github.com/ams-ts-ikvm/cn1-ikvm-uwp/blob/master/openjdk/sun/awt/IkvmDataTransferer.java#L95
Any ideas? Thanks!
There seems to be a workaround by not changing any code at all: The settings of the Release-build contain a checkbox if to use the .NET native toolbox for the build, which is enabled by default. By disabling that the build succeeds without any code change and is as fast as the Debug-build again. Before changing that, the Release-build took a lot longer as well.
Don't know what that means regarding actually calling native code, if that fails or not, because my app doesn't use those. I guess it would fail, depending on if it works in Debug or not. Additionally, I'm not sure if the Windows store accepts such a modified Release-build, but as UWP-apps aren't forced to use native code at all, I guess there's a good chance things are going to work.
I have problem with Boost.Interprocess (v1.66) library which I use in my C/C++ library which I use in C# through Marshalling (calling C native code from C#).
I found the problem if I was using Boost.Interprocess named_semaphore for sync between processes. (in open_or_create mode)
If I use my C/C++ lib with another native C/C++ code everything works fine (under newest Windows 10, Linux (4+ kernel) and even Mac OS X (>=10.11)).
The problem occurred under Windows - with C# I have C wrapper around C++ code. If I use Marshalling with simple own-build EXE --> Everything works! But If I use The same C# code (with the same C lib) in the third party application as a DLL plugin I got segfault from get_bootstamp in named_semaphore.
So I have third-party C# SW for which I create plugins (C# DLL). In that plugin I use my C library through marshalling. Marshalling work fine in test C# project (which just call C functions from C lib) but same code segfault in third-party SW.
C Library workflow:
Init all necessary C structures
Start desired TCP server (native C/C++ app) using Boost.Process
Wait for server (through named_semaphore) <-- segfault
Connect to the server...
C# code has same workflow.
Found the problem
The problem occured in boost::interprocess::ipcdetail::get_booststamp (which is called in named_semaphore). here:
struct windows_bootstamp
{
windows_bootstamp()
{
//Throw if bootstamp not available
if(!winapi::get_last_bootup_time(stamp)){
error_info err = system_error_code();
throw interprocess_exception(err);
}
}
//Use std::string. Even if this will be constructed in shared memory, all
//modules/dlls are from this process so internal raw pointers to heap are always valid
std::string stamp;
};
inline void get_bootstamp(std::string &s, bool add = false)
{
const windows_bootstamp &bootstamp = windows_intermodule_singleton<windows_bootstamp>::get();
if(add){
s += bootstamp.stamp;
}
else{
s = bootstamp.stamp;
}
}
If I debug to the line
const windows_bootstamp &bootstamp = windows_intermodule_singleton<windows_bootstamp>::get()
booststamp.stamp is not readable. The size is set to 31, capacity is set to some weird value (like 19452345) and the data is not readable. If i step over to
s += bootstamp.stamp;
the segfault occured!
Found the reason
I debug once more and set debug point to the windows_bootstamp constructor entry and I got no hit so the stamp is not initialized (I guess).
Confirmation
If I change get_bootstamp to
inline void get_bootstamp(std::string &s, bool add = false)
{
const windows_bootstamp &bootstamp = windows_intermodule_singleton<windows_bootstamp>::get();
std::string stamp;
winapi::get_last_bootup_time(stamp);
if(add){
s += stamp;
}
else{
s = stamp;
}
}
Recompile my lib and exe - everything works fine (without any problem).
My question is - what I am doing wrong? I read Boost.Interprocess doc really thoroughly but there are no advice/warnings about my problem (yeah there is "COM Initialization" in Interprocess doc but it not seems helpfull).
Or it's just a bug in Boost.interprocess and I may report it to Boost bug tracker?
Notice - if I start server manually (before I run C# code) It works without segfaults
I know the basic premise for creating a plug ins for Unity is to create a wrapper for all the classes you want to call from within Unity. However, all of the docs and examples I have found have all expected a corresponding .cpp (if c++) or .mm (if objective-c) file.
However I'm trying to create a plug in for some native iOS code that doesn't contain any source files. All I have access to is four header files and a single .a file. Which I have gotten from here.
Now, because I don't have any .mm files to wrap I'm a bit confused as to how I can go about bringing in these files into Unity so that I can call them from within. Has anyone ever done this before?
Can someone point me to some documentation, or anything that may help me, in bringing in 4 header files and .a file into Unity as a plug in?
Please remember, there are no source files that I have access to. Only the header files themselves.
You don't need source files, even the header files are not needed as long as you know the functions' declarations.
As described in Building Plugins for iOS:
1.) Put your .a file in Assets/Plugins/iOS
2.) Look at the header files to get the function signatures you need e.g.
void RegisterUnityIPodCallbackListener (const char* gameObject, const char* method);
3.) Declare RegisterUnityIPodCallbackListener within a C# class by:
public class IPodHandler {
[DllImport("__Internal")]
private static extern void RegisterUnityIPodCallbackListener (string gameObject, string method);
public static void MyRegisterUnityIPodCallbackListener () {
if (Application.platform == RuntimePlatform.IPhonePlayer) {
RegisterUnityIPodCallbackListener (GAME_OBJECT, METHOD);
}
}
}
4.) Call at an appropriate location:
IPodHandler.MyRegisterUnityIPodCallbackListener ("MyCallbackGameObject", "MyCallbackMethod");
Common pitfalls:
You should not build directory structures within Assets/Plugins/iOS otherwise files don't get copied to the generated Xcode project
Provide a fallback solution when testing in editor player
Here is another guide: How to build Unity3d Plugin for iOS
A few notes if you get an error something like "Undefined symbols for architecture..."
1) Make sure the used architecture in .a-file matches yours (for example armv7)
2) Make sure the .a-file is compiled with libstdc++ (GNU C++ standard library) since Unity requires that.
The Estimote SDK you're are using has ObjectiveC classes. Functions in ObjectiveC can't be called directly via a Unity plugin (either can C++ classes for that matter). The reason is that function names are managled when you compile.
The interface between a Unity C# class and a library must a pure C interface. That is why there is often .mm or .cpp files along side a .a file. These are to wrap a C++ or ObjectiveC class in a pure C wrapper.
Your job is a little easier because most of the Estimote functions seem to be class functions. So you don't need to write wrapper functions to create and delete NSObjects.
Here is an example I wrote, a pure C wrapper around the TestFlightSDK. https://github.com/notoes/TestFlightUnity/blob/master/src/TestFlightCBinding.mm
Notice the extern "C" block, forcing the file the code to be compiled without name mangling. A c function signature and then an ObjectiveC call within the function.
So using the Esitmote ESTBeacon class as an example, the connectToBeacon call could like this:
extern "C" {
void ESTBeacom_Connect()
{
[ESTBeacon connectToBeacon];
}
}
And the .cs function would look like this:
class ESTBeacon {
[DllImport ("__Internal")]
private static extern void ESTBeacon_Connect();
public static void Connect() {
if( Application.platform == RuntimePlatform.IPhonePlayer )
ESTBeacon_Connect()
}
}
Put the .cs, .mm and .a files in Plugins/iOS and you'll be all good.
Use this reference to find out how to pass various data types. http://www.mono-project.com/Interop_with_Native_Libraries
have been working on this for hours, couldn't get it work :(
below code gives exception "Attempted to read or write protected memory. This is often an indication that other memory is corrupt." this is fixed, see below update
but when i change the return type to int and return a int value, it works. how to make it to return a float value? thanks.
vs2012
c++ code
extern "C" __declspec(dllexport)
float compute_similarity()
{
return 1.01;
}
c# code
[DllImport("demo.exe", EntryPoint = "compute_similarity", CallingConvention = CallingConvention.Cdecl)]
public static extern float compute_similarity();
public void Get()
{
float x = compute_similarity(); // here returns random value
}
=====================================
UPDATE
See comments from David below, the problem was the c# project is targeting x64 and c++ is targeting Win32. After changing the c# project to target to x86, the exception went away.
However the call from c# returns some random value instead of 1.01 expected
I think your problem is that your function is declared in an executable rather than a DLL. Convert your native code into a library project and compile a DLL.
Your code will result in a call to LoadLibrary passing the file name demo.exe. The documentation for LoadLibrary says:
LoadLibrary can also be used to load other executable modules. For example, the function can specify an .exe file to get a handle that can be used in FindResource or LoadResource. However, do not use LoadLibrary to run an .exe file. Instead, use the CreateProcess function.
And so your code is doing exactly what you are told not to do. The call to LoadLibrary will succeed. The subsequent calls to GetProcAddress will succeed. But the module that you loaded is not fit to execute code.
Hey guys and girls :) ok so i ran this project ->
http://www.helyar.net/2009/libvlc-media-player-in-c-part-2/ and it worked perfectly (he was using .net 2.0) however when i try anything above 3.5 it gives ->
Unable to load DLL ‘libvlc’: The specified module could not be found. (Exception from HRESULT: 0x8007007E)
is there any workaround someone has done that sorts this out? MANY thanks ppl :D:D:D:D
There are two things that must be done when using that example with the new 2.0.x VLC releases. First, you have to somehow add the libvlc DLL to the search path. I used a call to SetDllDirectory to do the trick. You declare it as:
static class LibVlc
{
. . .
[DllImport("kernel32.dll", SetLastError = true)]
public static extern bool SetDllDirectory(string lpPathName);
. . .
}
Then you can call this method with the root folder of the VLC installation. On my PC, I called it as follows:
LibVlc.SetDllDirectory(#"C:\Program Files (x86)\VideoLAN\VLC");
Obviously, for a program being distributed this parameter should be configurable.
Next, the VLC API's have apparently changed because none of the methods require an exception object to be passed in anymore. It looks like return values from the methods should be checked (for example, libvlc_new() returns NULL if there was an error). I haven't tried passing in the exception object by reference like he does but the calls all work fine without it (and my interfaces now match the VLC API exactly). I also specify the calling convention to use when doing interop, just to be clear to the runtime what I expect for parameter passing order and such. For example, here are my defines for libvlc_new and libvlc_release:
[DllImport("libvlc", CallingConvention=CallingConvention.Cdecl)]
public static extern IntPtr libvlc_new(int argc,
[MarshalAs(UnmanagedType.LPArray,
ArraySubType = UnmanagedType.LPStr)] string[] argv);
[DllImport("libvlc", CallingConvention=CallingConvention.Cdecl)]
public static extern void libvlc_release(IntPtr instance);
I hope this helps!
You must copy libvlc.dll to your bin/debug folder. It must be the one from your VLC installation folder (C:\program files\videolan\vlc)