problems with LibraryFunctionLoad

egger · August 7, 2014, 2:04pm

Hi,
Im trying out Mathematica to connect our shared library to Mathematika but I have problems during running functions in the shared Library. So I started with a test shared library.
Some parts work fine so far. At first what worked:

1.	AppendTo[$LibraryPath,  ToFileName["/slowfs/lithop4-nb-2/egger/Mathematica/Tests"]];

2.	LibraryLoad["libtestlib"]

3.	INTTEST2 =  LibraryFunctionLoad["libtestlib", "Inttest2", {Integer, Integer}, Integer]

That worked so far. But running

INTTEST2[10, 101]

returned an error message:

LibraryFunction::rterr: An error with return code -1429266942 was encountered evaluating the function Inttest2. >>

I used Red Hat Enterprise Linux Client release 5.7 (Tikanga) and gcc version 4.1.2 20080704 (Red Hat 4.1.2-51).
Building the test shared library was done by

gcc -c -g -fPIC testlib.cpp -I.

gcc -shared -o libtestlib.so testlib.o

The console output from my shared library was:

Inttest2 parameter 1 is -1429266944 and parameter 2 is 2

Inttest parameter is -1429249280

I added two attachments testlib_header.txt that contains the header file testlib.h and testlib_source.txt in unix text format.

The interesting lines of the header are:

void Inttest1(int iTest);

int Inttest2(int iTest, int iTest2);

and of the cpp file are:

void Inttest1(int iTest)
{
std::cerr << "Inttest parameter is " << iTest << std::endl;
}

long Inttest2(long iTest, long iTest2)
{
std::cerr << "Inttest2 new parameter 1 is " << iTest << " and parameter 2 is " << iTest2 << std::endl;
long iSum = iTest + iTest2;
return iSum;
}

I hope you can help me with that problem.
Kind regards,
Roland

egger · August 8, 2014, 2:12pm

Hello,

has anybody any experience with LibraryFunctionLoad?

Kind regards,

Roland

nickl · August 8, 2014, 7:14pm

From looking at the source you posted, you haven’t included the WolframLibrary.h header or the DLLEXPORT type; have you gone through the LibraryLink “User Guide”?

In general, to call a function like this, you’ll need some sort of interface function like:

DLLEXPORT int demo1_I_I( WolframLibraryData libData, mint Argc, MArgument *Args, MArgument Res) {
	mint I0;
	mint I1;
	I0 = MArgument_getInteger(Args[0]);
	I1 = I0 + 1;
	MArgument_setInteger(Res, I1);
	return LIBRARY_NO_ERROR;
}

(this gets an integer from M_, add 1 to it, and then returns it to M_)

szhorvat · August 8, 2014, 8:24pm

It looks like there is a misunderstanding here. LibraryFunctionLoad is not meant for loading and calling arbitrary C functions. You will need to write C functions that follow specific rules before they can be loaded using LibraryFunctionLoad. Please see the LibraryLink user guide on how to do this.

egger · August 11, 2014, 8:42am

Hi Nick,
thank you for your answer. That is an interesting information. I tried to look into your link
http://reference.wolfram.com/language/LibraryLink/tutorial/LibraryStructure.htm
but I got only “Document Not Found”. [\Freaked smiley]
Oops, the page you are looking for cannot be found.

I found and read:

Ah, now I think I found it:

Let’s see if it helps me. If you have another link for me please send it.