[LLVMdev] Invalid or unaligned stack

Dibyendu Majumdar mobile at majumdar.org.uk
Mon Mar 30 15:59:19 PDT 2015


I am encountering a problem that I do not know how to debug. I would
greatly appreciate any guidance on this issue.

On Windows when I run Lua test cases from JITed code I am getting
following error:

Unhandled exception at 0x00007FFCEEEAC500 (ntdll.dll) in lua.exe:
0xC0000028: An invalid or unaligned stack was encountered during an
unwind operation.

This is happening when the Lua code is attempting to call longjmp().

The Lua test case that triggers this is a recursive call as shown below.

function err_on_n (n)
  if n==0 then error(); exit(1);
  else err_on_n (n-1); exit(1);

  function dummy (n)
    if n > 0 then
      assert(not pcall(err_on_n, n))


I have a struct that is created on the stack in the JIT compiler, and
this error is triggered when I add a field to the struct - if I remove
the field the error stops. The struct is not very large in size - it
is only 392 bytes with the new field.

If I allocate this struct on the heap the error goes away.

Note that just adding the field triggers the error even if I have no
other code changes.

The error occurs in Release build but not in Debug build.
I am using Visual C++ 2013 - 64-bit, and LLVM 3.6.0 on Windows.
I see no other unexpected behaviour - all the other tests pass.

All tests pass on Ubuntu, using LLVM 3.5.1 and gcc 4.8.2.

Of course I am currently assuming that somewhere my program is
corrupting memory - but as I have no other signs of a memory
corruption - the issue may be something else.

Any tips on what the problem might be would be gratefully received.

Thanks and Regards

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