Extendend memory is mapped over the main memory in the 0x4000..0x7FFF
area. Many DOSes disable interrupts while extended memory is banked in,
but not all (e.g. SpartaDOS-X).
This change modifies the initial interrupt handler to map in main memory
before chaining to the "worker" handlers.
Since the initial interrupt handler uses a data segment to store the
trampoline to chain to the original handler, introduce a new "LOWBSS"
segment to hold this trampoline. Otherwise the trampoline may end up
inside the 0x4000..0x7FFF area.
Add a link time warning if "LOWCODE" segment lays within the extended
memory window.
Although the primary target OS for the Apple II for sure isn't DOS 3.3 but ProDOS 8 the Apple II binary files contained a DOS 3.3 4-byte header. Recently I was made aware of the AppleSingle file format. That format is a much better way to transport Apple II meta data from the cc65 toolchain to the ProDOS 8 file system. Therefore I asked AppleCommander to support the AppleSingle file format. Now that there's an AppleCommander BETA with AppleSingle support it's the right time for this change.
I bumped version to 2.17 because of this from the perspective of Apple II users of course incompatible change.
The unexpanded Creativision has only $206 bytes of RAM available to cc65 programs. So it's a bad idea(tm) to reserve $180 bytes for the software stack. $40 bytes seems a much better default (aka guess).
The RAM memory area symbols are referred by the startup code. The 64k and 128k variant say "for assembler" so it may be not necessary to do that there. However given the "limited" state of documentation for the target I don't assign too much value to those statements.
Additionally it's unclear to me why two variants provide symbols for the ROM memory.
The Apple II hires screen buffer is located at $2000 (and can't be moved). The usual way to get along with this is to load the cc65 program above the hires screen buffer at $4000. However, that means that it becomes difficult to make good use of the memory below the hires screen buffer. The simplest approach is to add that memory to the heap. But there are programs containing just lots of code and not much data. One could think of moving the code to the area below the hires screen after loading (like it is done with the code for the language card). But if the program is really large (and already contains code to be moved to the language card) it won't just fit into memory in the first place.
The alternative is to load the program at the usual $803 and have it "cover" the hires screen buffer. Of course the part of the program that actually "covers" the hires screen buffer mustn't contain anything necessary for the program. The downside of this approach is that the program file on disk contains 8kB that can't be used by the program. But instead of just containing zeros the program can as well contain a hires screen picture that can be displayed right after startup.
Now the user can have code loaded below the hires screen buffer by setting the code-name to LOWCODE. However, he needs to explicitly do so. Otherwise the memory below the hires screen is totally wasted.
Trivia: Allowing to do this hires screen buffer "covering" was the very reason to change tgi_init() to not clear the hires screen anymore.
This change includes some cleanups, removal of mainargs.s (game console
programs never have arguments), and a workaround for a problem I'm seeing.
The problem is that sometimes (in fact, more often than not) the clrscr()
call in testcode/lib/joy-test.c writes some garbage chars on the screen (most
often a "P"). Could be my hardware (I haven't seen it on MAME), but to
me the root cause is still unknown.
