Code generated by one of the C compilers sets up the stack frame and
then maps the direct page on top of it. If the value at the top of
the stack is 16 bits, it will be referenced via address $ff. The
local variable editor was regarding this as illegal, because lvars are
currently only defined for direct page data, and the value doesn't
entirely fit there (unless you're doing an indirect JMP on an NMOS
6502, in which case it wraps around to $00... but let's ignore that).
The actual max width of a local variable is 257 because of the
possibility of a 16-bit access at $ff.
Older versions of SourceGen don't seem to have an issue when they
encounter this situation, as worrying about (start+width) is really
just an editor affectation. The access itself is still a direct-page
operation. You won't be able to edit the entry without reducing the
length, but otherwise everything works. I don't think there's a need
to bump the file version.
Added a compiled C implementation of strlen(). The most interesting
part about this is that it references a 16-bit value via direct-page
address $ff, which means you'd want a local variable with
address=$ff and width=2. The current UI prevents this.
Generate a 6502 test from the 65816 version by substituting the
16-bit instructions with 8-bit no-ops. There's a lot of project
edits and weird stuff in the test, so this was much easier than
starting over.
The 65816 variant is largely unchanged, though it could now be
stripped down to the stack-offset instructions.
