fix: relieve code overflow that crashed string operations#145
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The resident (non-paged) code section had overflowed past $C000 into kernel-reserved I/O space by $95 bytes. This stranded StringTempWrite across the $C000 boundary, so any operation building a temporary string (concatenation, STR$, CHR$, substrings) executed I/O space as code and crashed. Programs using string concatenation — e.g. ashanghai.bas — crashed on their first concat. Move the boot-only DisplayBannerText routine (and its macros) to a slot 3 kernel module, called once at boot via the generated thunk. The banner string/build data stays resident and is read from the module. This frees ~230 bytes of resident code; the $C000 overflow is gone and string temporaries sit safely below the boundary. Verified in MAME: no overflow warning, banner renders correctly, a$="x"+"y" works, STR$/CHR$/LEFT$/MID$/RIGHT$ work, and ashanghai.bas loads all assets and runs. Signed-off-by: Matthias Brukner <mbrukner@gmail.com>
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Problem
The resident (non-paged) code section had overflowed past
$C000into kernel-reserved I/O space by$95bytes — the standingBROKEN BUILDassembler warning. This strandedStringTempWriteacross the$C000boundary (its body ran into$C001+, which the F256 maps to I/O registers, not code). SinceStringTempWriteis called whenever a temporary string is built — string concatenation,STR$,CHR$, substrings — any such operation executed I/O space as code and crashed the machine.Programs relying on string concatenation crashed.
ashanghai.basdied on its first concat ("ashanghai/"+name$+".pal") during asset loading.Fix
Move the boot-only
DisplayBannerTextroutine (and its print macros) out of resident code into a slot 3 kernel module, called once at boot via the generated banking thunk. The banner's string/build data stays resident and is read from the module (resident code stays visible from slot 3). This frees ~230 bytes of resident code.Result: the
$C000overflow is gone, andStringTempWrite(now at$befc) sits safely below the boundary.Verification (MAME)
$C000overflow warning.a$="x"+"y"printsxy;STR$,CHR$,LEFT$,MID$,RIGHT$all work.ashanghai.basloads all assets and reaches the game.Note: this is a stopgap for the space pressure; the general fix is the paging rework.