Inconsistent handling of stack-underflow about pforth

[philburk]

In most of these cases, it was considered too costly to do the stack checking on these words. Words like + and * are meant to be optimized. The . prints so adding a stack check there was not too expensive.

When running the outer interpreter, I check at the end of the line. But not in the middle. I could add that.

2 3 drop drop   / no error
2 drop drop 3  / does not throw error but should because of temporary underflow

@MaxBarraclough - Would it help to add a compiler flag so that the primitives in pf_inner.c did underflow checking?
I could put some checks in the M_POP() and M_DROP() macros.

[MaxBarraclough]

@MaxBarraclough - Would it help to add a compiler flag so that the primitives in pf_inner.c did underflow checking? I could put some checks in the M_POP() and M_DROP() macros.

That sounds like a great solution. Are you thinking of 2 options (something like CHECKED/UNCHECKED) or 3 options (something like FULLY_CHECKED/PARTIALLY_CHECKED/UNCHECKED)?

If the performance penalty of full checking is significant, it might make good sense to default to partial checking, with the option of no checks at all for people looking for maximum performance.