Instantiate Cling without args?

Cling
1

I finally got Cling to work and link dynamically but I have a newer problem.

Is there a way I can instantiate the cling interpreter without argc and argv? I’m embedding Cling to an application through a C++ plugin interface, so there’s no way I can access argc and argv. I tried to pass bogus parameters to the cling::Interpreter constructor but it always crashes the program.

Any way to instantiate cling without args?

2

FWIW, this is ancient code from a prototype that used to work:

/* cling initialization --------------------------------------------------- */
namespace {

cling::Interpreter* gCppyy_Cling;
cling::MetaProcessor* gCppyy_MetaProcessor;

struct Cppyy_InitCling { // TODO: check whether ROOT/meta's TCling is linked in
    Cppyy_InitCling() {
        std::vector<std::string> cling_args_storage;
        cling_args_storage.push_back("cling4cppyy");

        // TODO: get this from env
        cling_args_storage.push_back("-I/home/wlavrijsen/rootdev/root/etc");

        std::vector<const char*> interp_args;
        for (std::vector<std::string>::const_iterator iarg = cling_args_storage.begin();
                iarg != cling_args_storage.end(); ++iarg)
           interp_args.push_back(iarg->c_str());

        // TODO: get this from env
        const char* llvm_resource_dir = "/home/wlavrijsen/rootdev/root/etc/cling";
        gCppyy_Cling = new cling::Interpreter(
            interp_args.size(), &(interp_args[0]), llvm_resource_dir);

        // fInterpreter->installLazyFunctionCreator(llvmLazyFunctionCreator);

        {
            // R__LOCKGUARD(gInterpreterMutex);
            gCppyy_Cling->AddIncludePath("/home/wlavrijsen/rootdev/root/etc/cling");
            gCppyy_Cling->AddIncludePath(".");
        }

        // don't check whether modules' files exist.
        gCppyy_Cling->getCI()->getPreprocessorOpts().DisablePCHValidation = true;

        // Use a stream that doesn't close its file descriptor.
        static llvm::raw_fd_ostream fMPOuts (STDOUT_FILENO, /* ShouldClose */ false);
        gCppyy_MetaProcessor = new cling::MetaProcessor(*gCppyy_Cling, fMPOuts);

        gCppyy_Cling->enableDynamicLookup();
    }
} _init;

} // unnamed namespace

It was created by stripping down to the bare minimum what ROOT does to initialize cling.

3

thank you very much wlav!
I’ve successfully loaded up cling with a working value!

cling::Interpreter *g_pInterp;

int main(void)
{
	std::vector<std::string> cling_args_storage;
	cling_args_storage.push_back("EmbedCling");

	// TODO: get this from env
	//cling_args_storage.push_back("-I/home/wlavrijsen/rootdev/root/etc");
	cling_args_storage.push_back("-I/home/kevin/SourceCodes/C++/Embedding Cling");

	std::vector< const char* > interp_args;
	{
		std::vector< std::string >::const_iterator iarg;
		for( iarg = cling_args_storage.begin() ; iarg != cling_args_storage.end() ; ++iarg )
			interp_args.push_back(iarg->c_str());
	}

	// TODO: get this from env
	//const char *llvm_resource_dir = "/home/wlavrijsen/rootdev/root/etc/cling";
	const char *llvm_resource_dir = "/home/kevin/SourceCodes/C++/Embedding Cling";
	g_pInterp = new cling::Interpreter(interp_args.size(), &(interp_args[0]), llvm_resource_dir);

	// fInterpreter->installLazyFunctionCreator(llvmLazyFunctionCreator);
	{
		// R__LOCKGUARD(gInterpreterMutex);
		g_pInterp->AddIncludePath("/home/kevin/SourceCodes/C++/Embedding Cling");
		g_pInterp->AddIncludePath(".");
	}
	
	class cling::Value val;
	enum cling::Interpreter::CompilationResult res = g_pInterp->process("int i = 5;", &val);
	printf("SMCLING Ext :: Loaded Successfully! -- res -> %i | value == %lli\n", res==cling::Interpreter::kSuccess, val.getLL());
	delete g_pInterp;
}

The last remaining issue is building a working path from the plugin extensions folder. I’ll try to figure that one on my own. Thanks again!