llvm dev - Nov 2019 - Crash using exceptions

Hello,

I get a crash in my program that uses exceptions and the LLVM JIT,
even though the exceptions are controlled and thrown/catched in a part
that doesn't deal with LLVM. I noticed that llvm-config --cxxflags
includes the -fno-exceptions flag. Do I need to throw no exceptions
whatsoever in my application to use LLVM JIT?

As a minimal example, I modified the code in
https://github.com/llvm-mirror/llvm/tree/master/examples/Kaleidoscope/BuildingAJIT/Chapter2.
In toy.cpp, I update LogError to throw an exception:

std::unique_ptr<ExprAST> LogError(const char *Str) {
  fprintf(stderr, "Error: %s\n", Str);
  throw std::runtime_error("");
}

and I catch that exception in MainLoop:

static void MainLoop() {
  while (true) {
    fprintf(stderr, "ready> ");
    try {
      switch (CurTok) {
      ...
      }
    } catch (std::runtime_error &e) {
      fprintf(stderr, "%s\n", e.what());
    }
  }
}

I compile with:

clang++ -g toy.cpp `llvm-config --cxxflags --ldflags --system-libs
--libs core orcjit native` -O3 -fexceptions -o toy
./toy
ready> var 3 = 2
ready> Error: expected identifier after var

ready> 1
terminate called after throwing an instance of 'std::bad_alloc'
  what():  std::bad_alloc
zsh: abort      ./toy

Technical details:
- LLVM latest master (commit 2c4ca6832fa6b306ee6a7010bfb80a3f2596f824)
on https://github.com/llvm-mirror/llvm.git
- clang version 8.0.0-3

Thank you,

-- 
Julien Lopez

Hi Julien,

You can turn on exceptions for your example by adding '-frtti
-fexceptions'
to your clang invocation:

clang++ -g toy.cpp `llvm-config --cxxflags --ldflags --system-libs --libs
core orcjit native` -frtti -fexceptions -O3 -fexceptions -o toy

You can also enable exception support and RTTI in your LLVM builds by
adding -DLLVM_ENABLE_RTTI=On -DLLVM_ENABLE_EH=On to your CMake invocation.

Cheers,
Lang.



On Mon, Nov 18, 2019 at 5:44 AM Julien Lopez via llvm-dev <
llvm-dev at lists.llvm.org> wrote:
> Hello,
>
> I get a crash in my program that uses exceptions and the LLVM JIT,
> even though the exceptions are controlled and thrown/catched in a part
> that doesn't deal with LLVM. I noticed that llvm-config --cxxflags
> includes the -fno-exceptions flag. Do I need to throw no exceptions
> whatsoever in my application to use LLVM JIT?
>
> As a minimal example, I modified the code in
>
>
https://github.com/llvm-mirror/llvm/tree/master/examples/Kaleidoscope/BuildingAJIT/Chapter2
> .
> In toy.cpp, I update LogError to throw an exception:
>
> std::unique_ptr<ExprAST> LogError(const char *Str) {
>   fprintf(stderr, "Error: %s\n", Str);
>   throw std::runtime_error("");
> }
>
> and I catch that exception in MainLoop:
>
> static void MainLoop() {
>   while (true) {
>     fprintf(stderr, "ready> ");
>     try {
>       switch (CurTok) {
>       ...
>       }
>     } catch (std::runtime_error &e) {
>       fprintf(stderr, "%s\n", e.what());
>     }
>   }
> }
>
> I compile with:
>
> clang++ -g toy.cpp `llvm-config --cxxflags --ldflags --system-libs
> --libs core orcjit native` -O3 -fexceptions -o toy
> ./toy
> ready> var 3 = 2
> ready> Error: expected identifier after var
>
> ready> 1
> terminate called after throwing an instance of 'std::bad_alloc'
>   what():  std::bad_alloc
> zsh: abort      ./toy
>
> Technical details:
> - LLVM latest master (commit 2c4ca6832fa6b306ee6a7010bfb80a3f2596f824)
> on https://github.com/llvm-mirror/llvm.git
> - clang version 8.0.0-3
>
> Thank you,
>
> --
> Julien Lopez
> _______________________________________________
> LLVM Developers mailing list
> llvm-dev at lists.llvm.org
> https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL:
<http://lists.llvm.org/pipermail/llvm-dev/attachments/20191121/00b59c4b/attachment.html>

Hi Lang,

Thank you for your reply. I didn't know about LLVM_ENABLE_RTTI and
LLVM_ENABLE_EH, I'll give it a try. I realized yesterday that my
minimal example doesn't actually capture the error I get in my real
application, my mistake. I'll investigate all of this and come back
with a better minimal example if I can't figure it out on my own.

Thanks again!

-- 
Julien

On Thu, 21 Nov 2019 at 21:01, Lang Hames <lhames at gmail.com>
wrote:
>
> Hi Julien,
>
> You can turn on exceptions for your example by adding '-frtti
-fexceptions' to your clang invocation:
>
> clang++ -g toy.cpp `llvm-config --cxxflags --ldflags --system-libs --libs
core orcjit native` -frtti -fexceptions -O3 -fexceptions -o toy
>
> You can also enable exception support and RTTI in your LLVM builds by
adding -DLLVM_ENABLE_RTTI=On -DLLVM_ENABLE_EH=On to your CMake invocation.
>
> Cheers,
> Lang.
>
>
>
> On Mon, Nov 18, 2019 at 5:44 AM Julien Lopez via llvm-dev <llvm-dev at
lists.llvm.org> wrote:
>>
>> Hello,
>>
>> I get a crash in my program that uses exceptions and the LLVM JIT,
>> even though the exceptions are controlled and thrown/catched in a part
>> that doesn't deal with LLVM. I noticed that llvm-config --cxxflags
>> includes the -fno-exceptions flag. Do I need to throw no exceptions
>> whatsoever in my application to use LLVM JIT?
>>
>> As a minimal example, I modified the code in
>>
https://github.com/llvm-mirror/llvm/tree/master/examples/Kaleidoscope/BuildingAJIT/Chapter2.
>> In toy.cpp, I update LogError to throw an exception:
>>
>> std::unique_ptr<ExprAST> LogError(const char *Str) {
>>   fprintf(stderr, "Error: %s\n", Str);
>>   throw std::runtime_error("");
>> }
>>
>> and I catch that exception in MainLoop:
>>
>> static void MainLoop() {
>>   while (true) {
>>     fprintf(stderr, "ready> ");
>>     try {
>>       switch (CurTok) {
>>       ...
>>       }
>>     } catch (std::runtime_error &e) {
>>       fprintf(stderr, "%s\n", e.what());
>>     }
>>   }
>> }
>>
>> I compile with:
>>
>> clang++ -g toy.cpp `llvm-config --cxxflags --ldflags --system-libs
>> --libs core orcjit native` -O3 -fexceptions -o toy
>> ./toy
>> ready> var 3 = 2
>> ready> Error: expected identifier after var
>>
>> ready> 1
>> terminate called after throwing an instance of 'std::bad_alloc'
>>   what():  std::bad_alloc
>> zsh: abort      ./toy
>>
>> Technical details:
>> - LLVM latest master (commit 2c4ca6832fa6b306ee6a7010bfb80a3f2596f824)
>> on https://github.com/llvm-mirror/llvm.git
>> - clang version 8.0.0-3
>>
>> Thank you,
>>
>> --
>> Julien Lopez
>> _______________________________________________
>> LLVM Developers mailing list
>> llvm-dev at lists.llvm.org
>> https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev