Hi Georg, Joel, Georg - Your question got me curious, so I wrote up a very basic implementation based on the clang-interpreter demo from clang/examples. I've tested it on Darwin with LLVM/Clang r249281 and it works, in its very limited way. I thought I would share it, in case it helps.
It sounds like Joel's project will be an excellent resource for a more serious approach. Cheers, Lang. On Sun, Oct 4, 2015 at 7:46 AM, Joel Andersson <j.a.e.anders...@gmail.com> wrote: > Hi Georg (and others interested in Clang+JIT), > > We just implemented this (Clang+JIT) in our open-source project CasADi ( > http://casadi.org). Feel free to have a look and/or reuse components. > > We used a plugin-design for using Clang, which is a bit different from the > examples we could find for using LLVM/Clang. We added a generic "Compiler" > class and made Clang/JIT a plugin for this Compiler class. Here is the > implementation of the plugin: > https://github.com/casadi/casadi/blob/develop/casadi/interfaces/clang/clang_compiler.cpp. > We also made a second plugin (only for Linux/Mac) which simply calls the > system compiler using shell commands. Mainly for benchmarking and when > Clang/JIT isn't available: > https://github.com/casadi/casadi/blob/develop/casadi/solvers/shell_compiler.cpp > . > > The trickiest was to set up the build system (we use CMake) and in > particular redistribute the C and C++ standard libraries needed to compile > any useful C/C++ code. And do it in a way that makes the compiled code > portable and not relying on e.g. setting environmental variables. > > This all works now, also on Windows, although it is not yet completely > mature (especially when trying to JIT compile C++ code). The solution used > in the LLVM examples was to use the arguments passed to "main", e.g. to > locate the "resource", but this didn't work for us since or tool is itself > a library and we don't have a "main". So the design we chose instead was to > place the compilation resources (including C/C++ standard library headers) > in a relative location to the plugin (which is a shared library) since the > path of the plugin can be retrieved at runtime by "dladdr" in Linux/Mac and > GetModuleHandleEx+GetModuleFileName on Windows. > > Best regards, > Joel > > > 2015-10-03 20:37 GMT+02:00 David Blaikie via cfe-users < > cfe-users@lists.llvm.org>: > >> >> >> On Sat, Oct 3, 2015 at 12:30 AM, Georg Bartels via cfe-users < >> cfe-users@lists.llvm.org> wrote: >> >>> Dear Clang Users, >>> >>> I have a particular programming problem, and several discussion forums >>> suggested Clang as a possible solution. Being totally new to Clang and its >>> community, is this the right place to ask questions about how to use Clang >>> for a particular programming task? If not, where should I turn to? >>> >>> In case this is the right forum for such questions, I continue >>> describing my problem. Basically, I want to compile a class which inherits >>> from a virtual interface class at runtime of my program. The program should >>> then create an instance of this new class and use it through its interface. >>> >>> Let me quickly sketch an example. The static version of my program would >>> look like this: >>> >>> class Base >>> { >>> public: >>> virtual int calc() const; >>> }; >>> >>> class Derived: public Base >>> { >>> public: >>> virtual int calc() const >>> { >>> return 42; >>> } >>> }; >>> >>> int main() >>> { >>> std::cout << Derived().calc() << std::endl; >>> return 0; >>> } >>> >>> >>> The dynamic version (with two fuzzy lines of code) shall look like this: >>> >>> class Base >>> { >>> public: >>> virtual void calc() const; >>> }; >>> >>> int main() >>> { >>> std::string code = read_derived_code(); >>> >>> // two fuzzy lines for which I am looking for a solution >>> SomeCompiledObjectClass o = compile(code); >>> Base* d = SomeFactoryClass(o).createInstance(); >>> >>> std::cout << d->calc() << std::endl; >>> return 0; >>> } >>> >>> Is Clang the right tool for solving my two fuzzy lines of code? If yes, >>> which class should have a look at? If not, do you maybe know about another >>> library/compile which can achieve this task? >>> >> >> This migth be the sort of thing that would escalate to cfe-dev and/or >> llvm-dev. >> >> What you're looking to do is JIT (Just In Time) compile some code. That >> involves using clang to turn the source code into LLVM IR and then LLVM to >> make machine code from that, put it in memory, make it executable, and call >> some part of it. >> >> Your two fuzzy lines of code would look slightly different (chances are >> what you'd do is generate source code that included a private function that >> return an instance, then you would JIT compile that function, indirectly >> code generating anything in the class that was needed, etc). >> >> I'm not sure where the best examples of the Clang half of this problem >> are. But for the second have, LLVM has the Kaleidoscope tutorials >> (especially the recently added ORC examples) that show how to use LLVM as a >> JIT compiler. You shuold be able to wrap up all these APIs into a fairly >> simple API for your one specific use case. >> >> I think /maybe/ out there is an existing C++ rapid development >> environment using Clang (essentially a C++ interpreter/interactive command >> prompt like Python) that you might be able to grab the basics of "feed code >> to compiler, get IR" from. >> >> - David >> >> >>> >>> Thanks a lot for your help! >>> >>> Cheers, >>> Georg. >>> >>> _______________________________________________ >>> cfe-users mailing list >>> cfe-users@lists.llvm.org >>> http://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-users >>> >> >> >> _______________________________________________ >> cfe-users mailing list >> cfe-users@lists.llvm.org >> http://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-users >> >> > > > -- > -- > Joel Andersson, PhD > Ptge. Busquets 11-13, atico 3 > E-08940 Cornella de Llobregat (Barcelona), Spain > Home: +34-93-6034011 > Mobile: +34-63-4408800 (in Sweden also +46-707-360512) >
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