[LLVMdev] Weird problems on calling an external function from MCJIT on Windows(mingw)

[waxiadao@gmail.com]

I'd like to take all my code here to make things easier,they are stil unble
to run properly.
cpp code: http://paste.ofcode.org/uNxEMvQTkZyjg2RTwjmXhh
IR code  : http://paste.ofcode.org/hhkFUz8weGKSUXXZZnNuEp
Thanks



2014-04-04 16:38 GMT+08:00 waxiadao at gmail.com <waxiadao at gmail.com>:

> oh,I'm sorry to make such a stupid mistake...But I still have to tell the
> correct one still didnt make difference...so weird
>
> 2014-04-04 16:30 GMT+08:00 Anton Korobeynikov <anton at korobeynikov.info>:
>
> Are you sure, that LLVMGetNamedFunction(m,"_a_outside_func") does not
>> return NULL? I believe it should be
>> LLVMGetNamedFunction(m,"a_outside_func")
>>
>> On Fri, Apr 4, 2014 at 12:25 PM, waxiadao at gmail.com <waxiadao at gmail.com>
>> wrote:
>> > Hello
>> > I quite thank you for your advice,but I have to tell that it made no
>> > difference too calling
>> >
>> "LLVMAddGlobalMapping(ee,LLVMGetNamedFunction(m,"_a_outside_func"),(void*)(&a_outside_func));".
>> >
>> >
>> > 2014-04-04 16:10 GMT+08:00 Anton Korobeynikov <anton at korobeynikov.info
>> >:
>> >
>> >> Hello
>> >>
>> >> While there is a symbol in the object file, there is nothing like this
>> >> in the final executable (well, you can try to export functions from
>> >> PE/COFF executable, but this is pretty non-standard technique). This
>> >> is the biggest difference wrt linux, where all the visible symbols are
>> >> exported by default from the binary.
>> >>
>> >> Most probably, the best way here is to create an explicit mapping
>> >> between a GlobalValue which represents your external function and the
>> >> address of your function. ExecutionEngine::addGlobalMapping() is your
>> >> friend here.
>> >>
>> >> On Fri, Apr 4, 2014 at 9:48 AM, waxiadao at gmail.com <waxiadao at gmail.com
>> >
>> >> wrote:
>> >> > Hi,
>> >> > I have a IR file generated by Clang:
>> >> >
>> >> > ; ModuleID = 'test_load_lib.c'
>> >> > target datalayout =
>> >> >
>> >> >
>> "e-p:32:32:32-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-f80:128:128-v64:64:64-v128:128:128-a0:0:64-f80:32:32-n8:16:32-S32"
>> >> > target triple = "i686-pc-mingw32"
>> >> >
>> >> > declare i32 @a_outside_func(i32)
>> >> >
>> >> > define i32 @test_func() {
>> >> > entry:
>> >> >   %call = call i32 @a_outside_func(i32 15)
>> >> >   ret i32 %call
>> >> > }
>> >> >
>> >> > where a_outside_func is a function defined on my code:
>> >> >
>> >> > extern "C" int a_outside_func(int a)
>> >> > {
>> >> >   return a + 50;
>> >> > }
>> >> >
>> >> > and following code is to get MCJIT work:
>> >> >
>> >> > #define prt(x) if(x) { cout << x << endl; }
>> >> > LLVMInitializeAllTargets();
>> >> >   LLVMInitializeAllTargetMCs();
>> >> >   LLVMInitializeAllTargetInfos();
>> >> >   LLVMInitializeAllAsmParsers();
>> >> >   LLVMInitializeAllAsmPrinters();
>> >> >   LLVMInitializeAllDisassemblers(); // just initialize them all....
>> >> >   prt(a_outside_func(50));               // afraid of linker optmize
>> it
>> >> > out
>> >> >
>> >> >   char *err = 0;
>> >> >   LLVMMemoryBufferRef ll_f = 0;
>> >> >   LLVMModuleRef m = 0;
>> >> >
>> >> >
>> LLVMCreateMemoryBufferWithContentsOfFile("test_load_lib.ll",&ll_f,&err);
>> >> > //read .ll
>> >> >   prt(err);
>> >> >   LLVMParseIRInContext(LLVMGetGlobalContext(),ll_f,&m,&err); // ll_f
>> >> > doesnt
>> >> > need freeing
>> >> >   prt(err);
>> >> >   LLVMDumpModule(m);
>> >> >
>> >> >   LLVMLinkInMCJIT();
>> >> >   LLVMExecutionEngineRef ee = 0;
>> >> >   LLVMCreateMCJITCompilerForModule(&ee,m,0,0,&err);
>> >> >   prt(err);
>> >> >   using tf_t = int ();
>> >> >   tf_t *f =
>> >> >
>> (tf_t*)LLVMGetPointerToGlobal(ee,LLVMGetNamedFunction(m,"test_func"));
>> >> >
>> >> > At first i got "LLVM ERROR: Incompatible object format! "
>> >> > But by reading some articles I append
>> >> > LLVMSetTarget(m,"i686-pc-mingw32");
>> >> > and it's fixed.
>> >> > Then I got "LLVM ERROR: Program used external function
>> 'a_outside_func'
>> >> > which could not be resolved!".
>> >> > I assumed my program didn't export the symbol properly.Thus,I use nm
>> to
>> >> > check my program's export and I found "a_outside_func" was renamed to
>> >> > "_a_outside_func"
>> >> > .
>> >> > For it I rename the function name in the IR to "_a_outside_func".But
>> it
>> >> > seemed to make no difference: "LLVM ERROR: Program used external
>> >> > function
>> >> > '_a_outside_func' which could not be resolved!".
>> >> > .............
>> >> > After a day's wasting I unconsciously packed my external function
>> >> > "a_outside_func" into a shared object,called
>> >> > llvm::sys::DynamicLibrary::LoadLibraryPermanently("ext_func.so"); at
>> the
>> >> > beginning of the program and named the function "_a_outside_func" in
>> the
>> >> > IR.
>> >> > OMG IT WORKS THEN?!
>> >> > So I'd like to ask why llvm cant resolve my external function from
>> the
>> >> > program itself(in fact i dont get such problems on linux)?
>> >> >
>> >> > _______________________________________________
>> >> > LLVM Developers mailing list
>> >> > LLVMdev at cs.uiuc.edu         http://llvm.cs.uiuc.edu
>> >> > http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev
>> >> >
>> >>
>> >>
>> >>
>> >> --
>> >> With best regards, Anton Korobeynikov
>> >> Faculty of Mathematics and Mechanics, Saint Petersburg State University
>> >
>> >
>>
>>
>>
>> --
>> With best regards, Anton Korobeynikov
>> Faculty of Mathematics and Mechanics, Saint Petersburg State University
>>
>
>
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