llvm dev - Jan 2019 - Kaleidoscope tutorial: extern functions failing

Hi all,

I am new to LLVM and have been working through the Kaleidoscope tutorial.
Everything is working fine so far except for local externs (as opposed to
things like the math functions, which are working). Note that I have seen
this bug with the reference code listing, as well as my own code. link to
code: https://llvm.org/docs/tutorial/LangImpl05.html#full-code-listing

[c34n10 kaleidoscope] ./toy
ready> extern sin(x); sin(1);
ready> Read extern:
declare double @sin(double)

ready> ready> Evaluated to 0.841471
ready> extern putchard(x); putchard(120);
ready> Read extern:
declare double @putchard(double)

ready> ready> Failure value returned from cantFail wrapped call
UNREACHABLE executed at ~/project/llvm/include/llvm/Support/Error.h:732!
Aborted (core dumped)

sin is, of course, defined in libm. putchard is declared in my code, per
the tutorial, as

/// putchard - putchar that takes a double and returns 0.
extern "C" DLLEXPORT double putchard(double X) {
  fputc((char)X, stderr);
  return 0;
}

Other posts online suggest that this issue could be caused by not compiling
with -rdynamic, but I am.

The actual error is occuring with the following code (on the cantFail line)

auto ExprSymbol = TheJIT->findSymbol("__anon_expr");
assert(ExprSymbol && "Function not found");

// cast to double-returning function
double (*FP)() = (double (*)())(intptr_t)cantFail(ExprSymbol.getAddress());
fprintf(stderr, "Evaluated to %f\n", FP());

and some investigation with GDB reveals that the hasError flag of
ExprSymbol.getAddress() is true, which is why the cantFail is failing. As
to why that flag is set, I'm at a loss. I have run through GDB with both
the sin and putchard examples, to try and see where they are diverging. I'm
not totally sure, but I think the divergence might be happening on line 347
of RuntimeDyld.cpp:

if (auto IOrErr = processRelocationRef(SectionID, I, Obj, LocalSections,
Stubs))

That is, in the sin example, this expression is false; in the putchard
example, it is true. However there may be something earlier on that I
missed – there were a few thousand lines of GDB logging to diff through.

It appears not to be an issue with the function itself, nor the
compilation/link process: from within GDB, I can successfully run call
putchard(120), so the symbol is definitely being included in the
executable. Just for some reason the JIT can't find it.

Finally, my makefile looks like

LIBS=core orcjit native analysis executionengine instcombine object
runtimedyld scalaropts support
FLAGS=`llvm-config --cxxflags --ldflags --system-libs --libs $(LIBS)`

%: %.cpp
        clang++ -v -g3 -O0 $^ -o $@ $(FLAGS) -rdynamic

Please let me know if I can provide any additional code or debug
information. I don't know a ton about LLVM so am a bit lost as to where to
go from here.

(Note: I also have posted this question on the LLVM IRC channel, and on
Stack
<https://stackoverflow.com/questions/54048268/llvm-kaleidoscope-tutorial-failing-on-local-extern>
.)

Thank you so much! I'm very excited to start working with LLVM and have
just been stuck on this issue for a couple of days.

Best,
Eli Baum
eli.baum at yale.edu
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Hi Eli,

Could you replace this code:

double (*FP)() = (double (*)())(intptr_t)cantFail(ExprSymbol.getAddress());

with:

double (*FP)() = nullptr;
if (auto ExprAddr = ExprSymbol.getAddress())
  FP = (double(*)())*ExprAddr;
else {
  logAllUnhandledErrors(ExprAddr.takeError(), llvm::errs(), "kaleidoscope
error:");
  exit(1);
}

Then reproduce the error?

That should allow us to log the error that RuntimeDyld is returning from
processRelocationRef. I guess this will be an unimplemented relocation on
Windows. It will be helpful to know which one it is.

Cheers,
Lang.


On Sun, Jan 6, 2019 at 6:45 PM Eli Baum via llvm-dev <
llvm-dev at lists.llvm.org> wrote:
> Hi all,
>
> I am new to LLVM and have been working through the Kaleidoscope tutorial.
> Everything is working fine so far except for local externs (as opposed to
> things like the math functions, which are working). Note that I have seen
> this bug with the reference code listing, as well as my own code. link to
> code: https://llvm.org/docs/tutorial/LangImpl05.html#full-code-listing
>
> [c34n10 kaleidoscope] ./toy
> ready> extern sin(x); sin(1);
> ready> Read extern:
> declare double @sin(double)
>
> ready> ready> Evaluated to 0.841471
> ready> extern putchard(x); putchard(120);
> ready> Read extern:
> declare double @putchard(double)
>
> ready> ready> Failure value returned from cantFail wrapped call
> UNREACHABLE executed at ~/project/llvm/include/llvm/Support/Error.h:732!
> Aborted (core dumped)
>
> sin is, of course, defined in libm. putchard is declared in my code, per
> the tutorial, as
>
> /// putchard - putchar that takes a double and returns 0.
> extern "C" DLLEXPORT double putchard(double X) {
>   fputc((char)X, stderr);
>   return 0;
> }
>
> Other posts online suggest that this issue could be caused by not
> compiling with -rdynamic, but I am.
>
> The actual error is occuring with the following code (on the cantFail line)
>
> auto ExprSymbol = TheJIT->findSymbol("__anon_expr");
> assert(ExprSymbol && "Function not found");
>
> // cast to double-returning function
> double (*FP)() = (double (*)())(intptr_t)cantFail(ExprSymbol.getAddress());
> fprintf(stderr, "Evaluated to %f\n", FP());
>
> and some investigation with GDB reveals that the hasError flag of
> ExprSymbol.getAddress() is true, which is why the cantFail is failing. As
> to why that flag is set, I'm at a loss. I have run through GDB with
both
> the sin and putchard examples, to try and see where they are diverging.
I'm
> not totally sure, but I think the divergence might be happening on line 347
> of RuntimeDyld.cpp:
>
> if (auto IOrErr = processRelocationRef(SectionID, I, Obj, LocalSections,
> Stubs))
>
> That is, in the sin example, this expression is false; in the putchard
> example, it is true. However there may be something earlier on that I
> missed – there were a few thousand lines of GDB logging to diff through.
>
> It appears not to be an issue with the function itself, nor the
> compilation/link process: from within GDB, I can successfully run call
> putchard(120), so the symbol is definitely being included in the
> executable. Just for some reason the JIT can't find it.
>
> Finally, my makefile looks like
>
> LIBS=core orcjit native analysis executionengine instcombine object
> runtimedyld scalaropts support
> FLAGS=`llvm-config --cxxflags --ldflags --system-libs --libs $(LIBS)`
>
> %: %.cpp
>         clang++ -v -g3 -O0 $^ -o $@ $(FLAGS) -rdynamic
>
> Please let me know if I can provide any additional code or debug
> information. I don't know a ton about LLVM so am a bit lost as to where
to
> go from here.
>
> (Note: I also have posted this question on the LLVM IRC channel, and on
> Stack
>
<https://stackoverflow.com/questions/54048268/llvm-kaleidoscope-tutorial-failing-on-local-extern>
> .)
>
> Thank you so much! I'm very excited to start working with LLVM and have
> just been stuck on this issue for a couple of days.
>
> Best,
> Eli Baum
> eli.baum at yale.edu
>
> _______________________________________________
> LLVM Developers mailing list
> llvm-dev at lists.llvm.org
> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>
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Hi Lang,

Here you go:

[c34n09 kaleidoscope] ./kld
kaleidoscope interpreter
kld> extern putchard(x); putchard(120);
kaleidoscope error:Symbols not found: { putchard }
pure virtual method called
terminate called without an active exception
Aborted (core dumped)

Also, I'm on Linux (RHEL 7.4). I did see in a source file some kind of
Windows extern issue, but that's not relevant here... :/

Thanks so much for your help,
Eli

On Tue, Jan 8, 2019 at 3:49 PM Lang Hames <lhames at gmail.com> wrote:
> Hi Eli,
>
> Could you replace this code:
>
> double (*FP)() = (double (*)())(intptr_t)cantFail(ExprSymbol.getAddress());
>
> with:
>
> double (*FP)() = nullptr;
> if (auto ExprAddr = ExprSymbol.getAddress())
>   FP = (double(*)())*ExprAddr;
> else {
>   logAllUnhandledErrors(ExprAddr.takeError(), llvm::errs(),
"kaleidoscope
> error:");
>   exit(1);
> }
>
> Then reproduce the error?
>
> That should allow us to log the error that RuntimeDyld is returning from
> processRelocationRef. I guess this will be an unimplemented relocation on
> Windows. It will be helpful to know which one it is.
>
> Cheers,
> Lang.
>
>
> On Sun, Jan 6, 2019 at 6:45 PM Eli Baum via llvm-dev <
> llvm-dev at lists.llvm.org> wrote:
>
>> Hi all,
>>
>> I am new to LLVM and have been working through the Kaleidoscope
tutorial.
>> Everything is working fine so far except for local externs (as opposed
to
>> things like the math functions, which are working). Note that I have
seen
>> this bug with the reference code listing, as well as my own code. link
to
>> code: https://llvm.org/docs/tutorial/LangImpl05.html#full-code-listing
>>
>> [c34n10 kaleidoscope] ./toy
>> ready> extern sin(x); sin(1);
>> ready> Read extern:
>> declare double @sin(double)
>>
>> ready> ready> Evaluated to 0.841471
>> ready> extern putchard(x); putchard(120);
>> ready> Read extern:
>> declare double @putchard(double)
>>
>> ready> ready> Failure value returned from cantFail wrapped call
>> UNREACHABLE executed at
~/project/llvm/include/llvm/Support/Error.h:732!
>> Aborted (core dumped)
>>
>> sin is, of course, defined in libm. putchard is declared in my code,
per
>> the tutorial, as
>>
>> /// putchard - putchar that takes a double and returns 0.
>> extern "C" DLLEXPORT double putchard(double X) {
>>   fputc((char)X, stderr);
>>   return 0;
>> }
>>
>> Other posts online suggest that this issue could be caused by not
>> compiling with -rdynamic, but I am.
>>
>> The actual error is occuring with the following code (on the cantFail
>> line)
>>
>> auto ExprSymbol = TheJIT->findSymbol("__anon_expr");
>> assert(ExprSymbol && "Function not found");
>>
>> // cast to double-returning function
>> double (*FP)() = (double
>> (*)())(intptr_t)cantFail(ExprSymbol.getAddress());
>> fprintf(stderr, "Evaluated to %f\n", FP());
>>
>> and some investigation with GDB reveals that the hasError flag of
>> ExprSymbol.getAddress() is true, which is why the cantFail is failing.
As
>> to why that flag is set, I'm at a loss. I have run through GDB with
both
>> the sin and putchard examples, to try and see where they are diverging.
I'm
>> not totally sure, but I think the divergence might be happening on line
347
>> of RuntimeDyld.cpp:
>>
>> if (auto IOrErr = processRelocationRef(SectionID, I, Obj,
LocalSections,
>> Stubs))
>>
>> That is, in the sin example, this expression is false; in the putchard
>> example, it is true. However there may be something earlier on that I
>> missed – there were a few thousand lines of GDB logging to diff
through.
>>
>> It appears not to be an issue with the function itself, nor the
>> compilation/link process: from within GDB, I can successfully run call
>> putchard(120), so the symbol is definitely being included in the
>> executable. Just for some reason the JIT can't find it.
>>
>> Finally, my makefile looks like
>>
>> LIBS=core orcjit native analysis executionengine instcombine object
>> runtimedyld scalaropts support
>> FLAGS=`llvm-config --cxxflags --ldflags --system-libs --libs $(LIBS)`
>>
>> %: %.cpp
>>         clang++ -v -g3 -O0 $^ -o $@ $(FLAGS) -rdynamic
>>
>> Please let me know if I can provide any additional code or debug
>> information. I don't know a ton about LLVM so am a bit lost as to
where to
>> go from here.
>>
>> (Note: I also have posted this question on the LLVM IRC channel, and on
>> Stack
>>
<https://stackoverflow.com/questions/54048268/llvm-kaleidoscope-tutorial-failing-on-local-extern>
>> .)
>>
>> Thank you so much! I'm very excited to start working with LLVM and
have
>> just been stuck on this issue for a couple of days.
>>
>> Best,
>> Eli Baum
>> eli.baum at yale.edu
>>
>> _______________________________________________
>> LLVM Developers mailing list
>> llvm-dev at lists.llvm.org
>> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>>
>
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