Is there any work around for using the "import" function when coverting a matlab *.m file to a C++ executable?
Matlab gives me this response: "Import statements are currently unsupported." and I just wanted to know if I was SOL or not.
Thanks
import makes Java classes available to Matlab programs. Since doing so makes it necessary to actually have a running Java Runtime Environment, I think it would be very costly to provide this functionality to generated C++ code – while it is always present when running the original m-file. I therefore would interpret the error message to say exactly what it says: "unsupported".
To be more precise and give references: MATLAB Language Features Supported for C/C++ Code Generation explicitly says that Java is not supported, but Matlab classes are. Moreover, import is not contained in the list of Functions Supported for C/C++ Code Generation.
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I have a huge amount of code written in Pascal and I need to use it in a C++ application running on an embedded PC with ARM9 processor. My idea was cross compiling Pascal code to dll libraries which I wanted to include in my C++ app. I tried to install Lazarus but I can't get work its cross compiler and I tried to install compiler directly to the embedded PC with similar result. C++ cross compiler works perfectly. Is there any way how to get Pascal code working in C++ application on different platform? I will provide any additional info if needed.
Additional info:
the embedded pc is for use in extremely low temperatures so it has low ram (32MB) running a trimmed Linux and there is only a little free space left on its flash memory (i have to use the SD card for all files)
I don't think anyone can conclusively answer your question, but some hints:
You will need to find a way to communicate between the C++ and Pascal code. This may simply be a case of defining any interface function as a C or C++ style function. But for example strings in Pascal are often NOT standard C or C++ style strings, so will need some extra handling to work out right. Structs (RECORD in pascal) and classes will require even more careful handling as to how they interface between the C++ and Pascal code - in most cases, it will become a full marshalling solution (that is, convert to a byte-stream, and then convert back to correct type at the other end).
Cross compilation of the Pascal code relies on having a Pascal compiler that matches your Pascal code AND your target. If you can't compile your code to the correct target, all other parts of the project will fail... There is a "standard" for Pascal, but most compilers have a range of extensions.
Have you considered making the Pascal code a standalone application that produces results as a file, rather than directly interfacing to the C++ code? Reading a file that you can control the format of can be a much easier solution than trying to interface one language to another.
There is a Matlab function (h5write) that lets the user write output files in hdf5 format. This seems to work nicely when using the Matlab environment and Matlab files. However, when I try to generate C++ code out of the Matlab files, a conversion error arises. It appears that the code generator (Matlab Coder) cannot convert the h5write operation into C++ code.
Is there any way of getting around this issue? Efficiency is also important here since the data sets that need to be stored by the generated C++ executable are fairly large. If anybody could help me out here, it would make my day! :-)
MATLAB currently provide an interface for converting the code for h5write into C++ code. That being said, you can use MATLAB compiler to build an executable or dll. You can use this in your C++ code, but you will always need the MCR. If space is not a constraint, you can do this.
Otherwise, you can use the HDF5 API (http://www.hdfgroup.org/HDF5/doc/cpplus_RM/) and write code for writing into HDF5 file format and then use MATLAB Coder to link and compile.
I have written some mex (c++) code, i have used mxArrays, and few other Matlab functions, i am wondering is it possible to convert it to C++ code easily by including the appropriate header and making some minor changes ?
edit:
By "convert", i mean that i want to compile and run my code without relying (using) on matlab.
As mentioned in the comments above, making this work depends greatly on the nature of the MATLAB functions you are using. Since you have successfully ported much of your MATLAB code to C++, I suggest you continue doing so until you are no longer reliant on the MATLAB libraries to build.
Are there any toolbox functions you are relying on? If so this may be a bigger task than you realize.
Good luck!
You can make executable by using SimulinkCoder - so you can run it without Matlab ... but you still must use Matlab to make executable every time you make change in the code.
Make basic Simulink model with single S-function block in which you specify your mex file.
Use SimulinkCoder (Real Time Workshop) to make executable out of the Simulink model.
I'm trying to adjust some mathematical code I've written to allow for arbitrary functions, but I only seem to be able to do so by pre-defining them at compile time, which seems clunky. I'm currently using function pointers, but as far as I can see the same problem would arise with functors. To provide a simplistic example, for forward-difference differentiation the code used is:
double xsquared(double x) {
return x*x;
}
double expx(double x) {
return exp(x);
}
double forward(double x, double h, double (*af)(double)) {
double answer = (af(x+h)-af(x))/h;
return answer;
}
Where either of the first two functions can be passed as the third argument. What I would like to do, however, is pass user input (in valid C++) rather than having to set up the functions beforehand. Any help would be greatly appreciated!
Historically the kind of functionality you're asking for has not been available in C++. The usual workaround is to embed an interpreter for a language other than C++ (Lua and Python for example are specifically designed for being integrated into C/C++ apps to allow scripting of them), or to create a new language specific to your application with your own parser, compiler, etc. However, that's changing.
Clang is a new open source compiler that's having its development by Apple that leverages LLVM. Clang is designed from the ground up to be usable not only as a compiler but also as a C++ library that you can embed into your applications. I haven't tried it myself, but you should be able to do what you want with Clang -- you'd link it as a library and ask it to compile code your users input into the application.
You might try checking out how the ClamAV team already did this, so that new virus definitions can be written in C.
As for other compilers, I know that GCC recently added support for plugins. It maybe possible to leverage that to bridge GCC and your app, but because GCC wasn't designed for being used as a library from the beginning it might be more difficult. I'm not aware of any other compilers that have a similar ability.
As C++ is a fully compiled language, you cannot really transform user input into code unless you write your own compiler or interpreter. But in this example, it can be possible to build a simple interpreter for a Domain Specific Language which would be mathematical formulae. All depends on what you want to do.
You could always take the user's input and run it through your compiler, then executing the resulting binary. This of course would have security risks as they could execute any arbitrary code.
Probably easier is to devise a minimalist language that lets users define simple functions, parsing them in C++ to execute the proper code.
The best solution is to use an embedded language like lua or python for this type of task. See e.g. Selecting An Embedded Language for suggestions.
You may use tiny C compiler as library (libtcc).
It allows you to compile arbitrary code in run-time and load it, but it is only works for C not C++.
Generally the only way is following:
Pass the code to compiler and create shared object or DLL
Load this Shared object or DLL
Use function from this shared object.
C++, unlike some other languages like Perl, isn't capable of doing runtime interpretation of itself.
Your only option here would be to allow the user to compile small shared libraries that could be dynamically-loaded by your application at runtime.
Well, there are two things you can do:
Take full advantage of boost/C++0x lambda's and to define functions at runtime.
If only mathematical formula's are needed, libraries like muParser are designed to turn a string into bytecode, which can be seen as defining a function at runtime.
While it seems like a blow off, there are a lot of people out there who have written equation parsers and interpreters for c++ and c, many commercial, many flawed, and all as different as faces in a crowd. One place to start is the college guys writing infix to postfix translators. Some of these systems use paranthetical grouping followed by putting the items on a stack like you would find in the old HP STL library. I spent 30 seconds and found this one:
http://www.speqmath.com/tutorials/expression_parser_cpp/index.html
possible search string:"gcc 'equation parser' infix to postfix"
I have no experience with llvm or clang, yet. From what I read clang is said to be easily embeddable Wikipedia-Clang, however, I did not find any tutorials about how to achieve this. So is it possible to provide the user of a c++ application with scripting-powers by JIT compiling and executing user-defined code at runtime? Would it be possible to call the applications own classes and methods and share objects?
edit: I'd prefer a C-like syntax for the script-languge (or even C++ itself)
I don't know of any tutorial, but there is an example C interpreter in the Clang source that might be helpful. You can find it here: http://llvm.org/viewvc/llvm-project/cfe/trunk/examples/clang-interpreter/
You probably won't have much of a choice of syntax for your scripting language if you go this route. Clang only parses C, C++, and Objective C. If you want any variations, you may have your work cut out for you.
I think here's what exactly you described.
http://root.cern.ch/drupal/content/cling
You can use clang as a library to implement JIT compilation as stated by other answers.
Then, you have to load up the compiled module (say, an .so library).
In order to accomplish this, you can use standard dlopen (unix) or LoadLibrary (windows) to load it, then use dlsym (unix) to dynamically reference compiled functions, say a "script" main()-like function whose name is known. Note that for C++ you would have to use mangled symbols.
A portable alternative is e.g. GNU's libltdl.
As an alternative, the "script" may run automatically at load time by implementing module init functions or putting some static code (the constructor of a C++ globally defined object would be called immediately).
The loaded module can directly call anything in the main application. Of course symbols are known at compilation time by using the proper main app's header files.
If you want to easily add C++ "plugins" to your program, and know the component interface a priori (say your main application knows the name and interface of a loaded class from its .h before the module is loaded in memory), after you dynamically load the library the class is available to be used as if it was statically linked. Just be sure you do not try to instantiate a class' object before you dlopen() its module.
Using static code allows to implement nice automatic plugin registration mechanisms too.
I don't know about Clang but you might want to look at Ch:
http://www.softintegration.com/
This is described as an embeddable or stand-alone c/c++ interpreter. There is a Dr. Dobbs article with examples of embedding it here:
http://www.drdobbs.com/architecture-and-design/212201774
I haven't done more than play with it but it seems to be a stable and mature product. It's commercial, closed-source, but the "standard" version is described as free for both personal and commercial use. However, looking at the license it seems that "commercial" may only include internal company use, not embedding in a product that is then sold or distributed. (I'm not a lawyer, so clearly one should check with SoftIntegration to be certain of the license terms.)
I am not sure that embedding a C or C++ compiler like Clang is a good idea in your case. Because the "script", that is the (C or C++) code fed (at runtime!) can be arbitrary so be able to crash the entire application. You usually don't want faulty user input to be able to crash your application.
Be sure to read What every C programmer should know about undefined behavior because it is relevant and applies to C++ also (including any "C++ script" used by your application). Notice that, unfortunately, a lot of UB don't crash processes (for example a buffer overflow could corrupt some completely unrelated data).
If you want to embed an interpreter, choose something designed for that purpose, like Guile or Lua, and be careful that errors in the script don't crash the entire application. See this answer for a more detailed discussion of interpreter embedding.