Re: [perl #18127] [PATCH] Implicit stack direction probe

[Leopold Toetsch]

Jason Gloudon wrote:

... By default both compilers align stack variables at their natural
alignment, so PMC pointers would normally fall on 4 byte boundaries.

However, it is also possible that someone might save a PMC pointer to an
unaligned address on the stack (I can't imagine why). We could always say
"don't do that!" for performance reasons.

So, this "someone" are we (parrot itself) + language extensions (PXS) which have to be compiled with the same compiler options, parrot is compiled with.
Using packed structures with PMCs/Buffers inside is a strict "don't do that!".

Now, given above rules and _if_ each machine parrot is running on, aligns a (PMC *)p at sizeof(PMC*) on the stack, we can safely define our {lo,hi}_var_ptrs as PMC** and just iterate the $stack_p++.

If there are machines/compilers out there, that don't follow above rule, we put some #ifdefs in trace_system_stack for these.

This part is too time critical to program for the LCD.

leo