I'll preface this by saying I'm a C# programmer who inherited horrible code with no documentation. I have an unmanaged C++ library wrapped with managed code that worked fine in VS2003 with .Net 1.1 Framework. I'm trying to get it upgraded to at least .Net 2.0.
I have the unmanaged C++ library that was compiled with "MSVC 8.x" (thus equivalent to VS 2005, I assume). I've been trying to migrate everything to VS2008 and still have some issues with this library at runtime.
My question is this: should this library work with VS2008? Or should I be developing in VS2005 if the library was compiled with VC8.x?
Any thoughts would be greatly appreciated. Thanks!
It should work, I expect that you are having issues with your marshalling. It is probably stuff that was declared incorrectly for PInvoking that managed to work in .NET 1.1 but not in later versions.
You don't say what sort of problems you are having at run time, nor do you state how you access your library. For example, do you compile your library along with your project? If so, can you turn on unmanaged debugging in your C# project and step into the code you are having trouble with? How are you calling the unmanaged code? Is it through PInvoke, or do you have managed C++ wrappers?
In my experience, the best solution for calling out to a legacy unmanaged library is to add a managed wrapper library for your legacy library written in managed C++. This way you present a managed interface for your library for all .NET languages to consume and you don't have to worry about getting your PInvoke signatures correct.
Your project should look something like this.
C# Application -> Manage C++ Wrapper DLL -> Legacy DLL
It can depend what else the lib relies on. For example, if you are using the STL across the library interfaces then it would be a bad idea to have the library compiled with a different version to the client. However, if the library presents a simple C style function interface then you shouldn't have problems.
If you have the source code for the library then I would recommend trying to port it to VS2008. In general it is much less hassle in the long run to have everything in the same development environment.
How are you wrapping the unmanaged lib ... presumably using managed extensions for C++ if it dates back to VS2003. This is now deprecated and has been replaced with C++/CLI as of VS2005. Whilst the newer compilers support a /clr:oldSyntax switch to still compile the old code there are definitely issues with it. We have old code that will not compile on VS2005(8) using this switch.
--Rob Prouse:
The wrapper uses managed C++, no PInvoke. The wrapper is compiled into a DLL that is then used by another application (as you illustrated).
The legacy code produces graphics objects. When I try to get the handle to an image, I get a null exception instead. The debugger doesn't let me get farther into the code to figure out why. Everything else seems to run ok - the other data objects needed to create the image exist and appear to be correct. (Sorry, I know that is still a pretty vague description.)
--Rob Walker:
I unfortunately do not have the source code.
Not sure about "using the STL across the library interfaces". Does graphics fall under that category?
I was able to get my application to run with using the /clr:oldSyntax switch, but that's where I get the null handles to images. I tried to put in all the modifications so that it would compile with /clr, but then I kept getting link errors that I couldn't resolve. (The linker kept complaining about not being able to find files even though those files were in the folder where it was looking.)
Related
There is this library which is used as a reference by other programs: https://github.com/RetroAchievements/RASuite/tree/master/RA_Integration
I have downloaded the compiled programs (that come with the compiled library) and they work fine. My goal is to make a change in the library code, re-compile it and replace the DLL of the compiled programs I have downloaded with my own compiled DLL. Like so:
ProgramA.exe
|_ RA_Integration.dll < replace with my own (built)
Before even changing the code, I am just trying to compile the DLL and use it along the compiled programs I have downloaded. I am not willing to re-compile the programs themselves because it will be too much work because of dependencies etc. And I also would like to be able to just "ship" the DLL to whoever wants my fix.
So I have downloaded the source code of that library, re-compiled it myself successfully but when I use it instead of the one that comes with the programs, they do not start up (Windows Event Viewer say that there was a problem loading my DLL).
I am assuming that my system have differences with the system that built the original DLL and that it is the reason why it fails. My question is: can I find those differences? Although I am a professional .NET programmer (as in it's my job) I am a C++ newbie and I am having trouble to understand all those linker/precompiler/dependencies/c++ stuff that seem to give different builds/results from a machine to another.
All I have been able to find is that in the project properties the "Platform Toolset" is "Visual Studio 2013 - Windows XP (v120_xp)", therefore I have installed Visual Studio 2013 (with Update 5 since it seems Windows XP support was not present in base VS2013) but that seems to not be enough. I am running Windows 10, which was surely not the OS the original programmer used when they compiled the DLL a couple years ago, but not sure if that matters?
Is there anything that could be found from the DLL itself or from the project that would hint me as to what I need on my system?
Hope that makes sense.
Thanks
Before even changing the code, I am just trying to compile the DLL and use it along the compiled programs I have downloaded. I am not willing to re-compile the programs themselves because it will be too much work because of dependencies etc. And I also would like to be able to just "ship" the DLL to whoever wants my fix.
Here's your fallacy: your DLL is a linking dependency. You must re-build your application, because obviously, the ABI of the library changed, rendering it incompatible with what your program tries to call in functionality that it expects to be in the DLL.
There's no way around that short of building an ABI-compatible wrapper DLL using your precious programming knowledge :) Finding these differences is hard – because, you could for example export a symbol list from your DLL, which will basically contain all the functions that DLL "offers", but some aspects of how these functions need to be called aren't actually part of that and can only be deducted by a linker (or a skilled person with too much time on their hand and an unhealthy obsession for parsing things in their head) from the C++ source code.
In other words: you changed what you're run-time linking your program against. You must now rebuild your program. End of options!
I have C++ code, which I have managed to compile into an iOS static library ("library.a") using Xcode. I am then including this in my project (Xamarin.iOS, though this shouldn't matter) and have managed to get it working as expected. The code is c/c++ and doesn't reference any code from the iOSFrameworks. I was wondering if it would be possible to find a way to build this (just compile the library) without a mac computer.
Something like download the clang compiler on a windows machine and then build an "library.a" that is compatible with the arm architectures and thus will work if I include it in my iOS project.
I have tried doing some reading on the web which suggests that it wouldn't work, but they might not be working in my exact circumstances etc.
The reason behind my need for this is because the C++ part of the code base is maintained by someone else, and we require them to build the iOS compatible library without us having access to their code. They do not have access to a Mac.
Thanks very much for any help.
We have been moving our small application databases to SQLite at work and ran into an issue where one user who installed our program did not have the C++ runtimes. We are using System.Data.SQLite and the program would not work because of this, obviously.
My colleague has said that, for any library or system we implement, "if it requires C++ runtimes then use somehting else." It causes a lot of issues.
I know that SQLite is written in C++, but is there an implementation of any kind that is not? Is there an implementation that does not require the C++ runtimes in windows?
C#-SQLite is an independent reimplementation of the SQLite software library version 3.7.7.1.
It has been ported into managed code, written in C#
http://code.google.com/p/csharp-sqlite/
I need some help with wrapping C++ libraries in XCode.
What I want to achieve is to create new library in XCode, import C++ library (I have .a and .h files), wrap it to Obj-C so I can import that library to MonoTouch.
The reason why I do it round way is that when I try to import C++ lib into MonoTouch, because of name mangling I keep getting WrongEntryPoint exceptions. Correct me if I'm wrong but there is no way for me to find out mangled names, which depends on compiler.
Thank you in advance
Correct me if I'm wrong but there is no way for me to find out mangled names, which depends on compiler.
Technically you could. Many compilers share the same mangling syntax, maybe the most useful and long-lasting gift from Itanium ;-)
However it will bring it's own pain (e.g. non-primitive types, other compilers) and maintenance issues as you update your C++ code.
You'll better served by:
writing an ObjectiveC wrapper and use MonoTouch's btouch tool to generated bindings;
writing a C wrapper and using .NET p/invoke to call your code;
The choice it yours but if you think about reusing the C++/C# code elsewhere (e.g. Mono for Android) then using C and p/invoke will be reusable.
I would definitely recommend going the route of wrapping the library in an Obj-C library and using btouch to import the library into MonoTouch. I have recently done this for a C++ library that implemented a Sybase database engine. If you look at my questions you will find quite a few pertaining to wrapping C++ libraries as I posted a few times regarding issues I encountered.
Specifically, you can look at these questions:
Linking to a C++ native library in MonoTouch
Wrapping a C++ library in Objective-C is not hiding the C++ symbols
Application with static library runs on simulator but not on actual device
Undefined symbols when linking PhoneGap static library in MonoTouch
Linker options 'Link all assemblies" and "Link SDK assemblies only" causes undefined symbols in 3rd party static library
I would also recommend, if you are going to go the route of an Obj-C wrapper, that you get btouch to output code and include that in your project rather than including a dll from btouch. From my experience, the code worked more reliably than the dll, although the issues with the dll may have been resolved by now. But take a look at this question regarding the btouch issue:
Exception System.InvalidCastException when calling a method bound with btouch that returns an object. MonoTouch bug?
If you have specific questions/problems in building the Obj-C wrapper then ask them here and post some code and I am sure that I or other members of the community would be able to help you with it.
Bruce, as you assumed, I have problems with wrapping C++ code. After hours and hours of reading and trying, I couldn't wrap the C++ code.
Anyway, I managed to create a simple Obj-C library made of some dummy class, and then import it into another library. That worked fine. However, following same pattern, I included C++ .a file along with .h file (I'm not sure whether .h is mandatory because we can link header files in build options, right??) and when I compiled it, it went fine, the build succeeded, but XCode didn't produce new .a library.
I added linker flags: -ObjC -lNameOfLib
Does C++ Standard Library Type in Build - Linking has to be Static? And Symbols Hidden By Default as well?
It would be great if we could write step-by-step tut, since there are tons of various instructions, but I haven't been able to push it through the end.
I'm confused a bit..
Thank you guys...
I have a C++ dll file that uses a lot of other c++ librarys (IPP, Opencv +++) that I need to load into matlab. How can I do this?
I have tried loadlibrary and mex. The load library does not work.
The mex finds the linux things (platform independent library) and tries to include them. And that does not work.
Does anyone have any good ideas?
loadlibrary should work. I use it all the time to call functions from dlls written in C++ with C wrappers.
What errors are you getting when you try to use loadlibrary?
Make sure that the exported functions of the dll are C functions, not C++ functions. If not, then write C wrappers.
More info on exactly what you are doing when using loadlibrary would be helpful.
As mentioned by others, you should first wrap your C++ library as a C library - mathworks used to advise not to use C++ code directly in mex (dlopening C++ core directly is complicated), maybe it is still true.
Your description is quite unclear, too: what do you mean by "mex finds the linux thing", but that does not work. Saying that it does not work is not helpful: the exact commands and error message are.
You could go for the Java approach (since Matlab runs on a JRE and can access Java objects/methods -- just be aware that the Matlab JRE is not as up-to-date as the latest JRE, the one I'm running uses Java 1.5) and use JNA to access your DLL.
Or, if you wrote the top-level DLL, you could go for the COM/ActiveX approach.
I've had good success architecting the interface to my C++ functions as COM/ActiveX libraries -- you don't have to bother with that .h stuff.
See the External Interfaces guide on COM clients, particularly the part about managing/converting data.
It would be extra work to add the COM/ActiveX layer, but would make your library more portable within the Windows world and probably more easily used in MATLAB.
If you have a lot of function calls to your DLL, the COM/ActiveX approach might be faster (not sure), but otherwise I think the JNA approach would be easier.