Re: MPS: assertion failed: header_type (h) != IGC_OBJ_FWD

[Andrea Corallo]

Gerd Möllmann <gerd.moellmann@gmail.com> writes:

> Gerd Möllmann <gerd.moellmann@gmail.com> writes:
>
>> Gerd Möllmann <gerd.moellmann@gmail.com> writes:
>>
>>> Let's see if it continues crashing.
>>
>> It does :-(.
>
> Next idea.
>
> I wonder if __builtin_unwind_init changes things. The different
> behaviour when compiled -O0 and -O, the fact that problems happen in
> "random" places which lets me suspect indicates a basic problem, and so
> on - that would fit, when MPS doesn't see something in a register.
> Maybe.
>
> I'm now running with a patch that adds that to MPS' stack scanning code.
>
> @@ -39,6 +39,8 @@ void StackHot(void **stackOut);
>  /* STACK_CONTEXT_BEGIN -- save context */
>  
>  #define STACK_CONTEXT_BEGIN(arena) \
> +  BEGIN \
> +  __builtin_unwind_init(); \
>    BEGIN \
>      StackContextStruct _sc; \
>      STACK_CONTEXT_SAVE(&_sc); \
> @@ -51,6 +53,7 @@ void StackHot(void **stackOut);
>  /* STACK_CONTEXT_END -- clear context */
>  
>  #define STACK_CONTEXT_END(arena) \
> +    END; \
>      END; \
>      AVER(arena->stackWarm != NULL); \
>      arena->stackWarm = NULL; \
>
> If somone observes similar strange phenomena like I do on macOS/arm64,
> maybe also give it a try.
>
> Let's see how long igc survives this time :-).

Hi Gerd,

if you want to use '__builtin_unwind_init' be aware that this GCC bug
I've found sometime ago [1] might make the builtin ineffective.  It
might not effect your generated code but in case you need you can see
how we work it around in 'flush_stack_call_func'.

Regards

  Andrea


[1] <https://gcc.gnu.org/bugzilla/show_bug.cgi?id=115132>