[LLVMdev] MCJIT longjmp failure on Win64 - was Invalid or unaligned stack exception on Windows

[Dibyendu Majumdar]

On 28 April 2015 at 10:43, Paweł Bylica <chfast at gmail.com> wrote:
> I'm not sure what your requirements are. Can you specify why do you need
> longjmp?

Lua uses setjmp/longjmp to implement exception handling. It is the Lua
infrastructure code that is making these calls.
A JIT compiled function does not directly call either - but may call a
Lua C function that then invokes longjmp.
As the Lua code is written in C - I do not need C++ stack unwinding.

>
> The issue is your jump from longjmp call to setjmp location is crossing
> functions on callstack that were created by MCJIT. Those functions do not
> have proper stack unwinding information required by longjmp. The callstack
> looks like:
>
> setjmp, MSVC/C++
> other code, LLVM MCJIT
> longjmp, MSVC/C++
>
> Your solutions are:
>
> Pull longjmp call from C++ to LLVM IR. LLVM has a convenient intrinsic for
> that: llvm.longjmp. That solution is a bit fragile as that intrinsic will be
> lowered to C standard lib call, but if I remember correctly it worked for
> me. Windows might have 3 different implementation of longjmp: debug and
> release versions for C++ and C, maybe one of them is less fussy.
> Pull both longjmp and setjmp to LLVM IR. In that case you can switch from
> full-featured versions powered by standard library to lightweight builtin
> versions powered by LLVM (llvm.eh.sjlj.longjmp). Much better portability.
> In that second case, setting up llvm.eh.sjlj.setjmp correctly is a bit
> tricky. You need to place some data (as stack pointer) in the jump buffer
> manually. See
> http://lists.cs.uiuc.edu/pipermail/llvmdev/2015-February/081961.html
>>
>> I am also wondering if mingw gcc compilers have the same issue.
>
>
> MinGW has its own implementation of setjmp/longjmp. Its longjmp do not do
> C++ stack unwinding of course.

So the easiest option seems to be to compile using MingW ... I do not
need C++ stack unwinding so that should be fine.
I will also look at the built-ins - I can provide a JIT compiled
wrapper that can be invoked by the Lua C functions.

Many thanks for pointing me to this issue as I was wasting a lot of
time trying to figure out if there was a bug in my code that was
corrupting the stack.

Thanks and Regards
Dibyendu