crash in PUT in EGA modes

[incanus]

Bug report

Problem

In both Python 2 and 3, there are crash bugs with using PUT.

Steps

1. EGA screen modes 7-9
2. GET a sprite
3. Try to PUT it

Program

10 SIZE=20
20 DIM S(SIZE*SIZE)
30 SCREEN 7 : CLS
40 LINE(100,100)-(100+SIZE,100+SIZE),4,BF
50 GET(100,100)-(100+SIZE,100+SIZE),S
60 CLS
70 PLAY "p1 p1"
80 PUT(100,100),S

Crash log

Python 2:

PC-BASIC crash log
====================================================================================================
FATAL ERROR
version   2.0.3 [ unreleased ]
python    2.7.16 [64bit ] 
platform  Darwin-20.1.0-x86_64-i386-64bit
interface VideoSDL2, AudioSDL2
statement 80 PUT(100,100),S

statements.py:82, parse_statement
graphics.py:946, put_
framebuffer.py:159, unpack
bytematrix.py:209, frompacked
TypeError: object of type 'generator' has no len()

This is a bug in PC-BASIC.
Sorry about that. You can help improve PC-BASIC:

- Please file a bug report, including this message and the steps you took
  just before the crash. Go to:
    https://github.com/robhagemans/pcbasic/issues

- Please include the full crash log in your report.
  You can paste it from the clipboard or from the file at:
    /Users/incanus/Library/Application Support/pcbasic-2.0/crash-20201119-4uaynZ.log
Traceback (most recent call last):
  File "pcbasic/pcbasic/guard.py", line 51, in protect
    yield
  File "pcbasic/pcbasic/main.py", line 118, in _run_session
    session.execute(cmd)
  File "pcbasic/pcbasic/basic/api.py", line 91, in execute
    self._impl.execute(cmd)
  File "pcbasic/pcbasic/basic/implementation.py", line 252, in execute
    self.interpreter.loop()
  File "pcbasic/pcbasic/basic/interpreter.py", line 122, in loop
    self.parse()
  File "pcbasic/pcbasic/basic/interpreter.py", line 112, in parse
    self.parser.parse_statement(ins)
  File "pcbasic/pcbasic/basic/parser/statements.py", line 82, in parse_statement
    self._callbacks[c](parse_args(ins))
  File "pcbasic/pcbasic/basic/display/graphics.py", line 946, in put_
    sprite = self._mode.sprite_builder.unpack(packed_sprite)
  File "pcbasic/pcbasic/basic/display/framebuffer.py", line 159, in unpack
    packed, height=height*self._number_planes, items_per_byte=8
  File "pcbasic/pcbasic/basic/base/bytematrix.py", line 209, in frompacked
    width = len(packed) // height
TypeError: object of type 'generator' has no len()

Python 3:

PC-BASIC crash log
====================================================================================================
FATAL ERROR
version   2.0.3 [ unreleased ]
python    3.8.6 [64bit ] 
platform  macOS-10.16-x86_64-i386-64bit
interface VideoSDL2, AudioSDL2
statement 80 PUT(100,100),S

statements.py:82, parse_statement
graphics.py:946, put_
framebuffer.py:158, unpack
bytematrix.py:212, frompacked
ValueError: range() arg 3 must not be zero

This is a bug in PC-BASIC.
Sorry about that. You can help improve PC-BASIC:

- Please file a bug report, including this message and the steps you took
  just before the crash. Go to:
    https://github.com/robhagemans/pcbasic/issues

- Please include the full crash log in your report.
  You can paste it from the clipboard or from the file at:
    /Users/incanus/Library/Application Support/pcbasic-2.0/crash-20201119-2_t040qx.log
Traceback (most recent call last):
  File "pcbasic/pcbasic/guard.py", line 51, in protect
    yield
  File "pcbasic/pcbasic/main.py", line 119, in _run_session
    session.interact()
  File "pcbasic/pcbasic/basic/api.py", line 149, in interact
    self._impl.interact()
  File "pcbasic/pcbasic/basic/implementation.py", line 315, in interact
    self.interpreter.loop()
  File "pcbasic/pcbasic/basic/interpreter.py", line 122, in loop
    self.parse()
  File "pcbasic/pcbasic/basic/interpreter.py", line 112, in parse
    self.parser.parse_statement(ins)
  File "pcbasic/pcbasic/basic/parser/statements.py", line 82, in parse_statement
    self._callbacks[c](parse_args(ins))
  File "pcbasic/pcbasic/basic/display/graphics.py", line 946, in put_
    sprite = self._mode.sprite_builder.unpack(packed_sprite)
  File "pcbasic/pcbasic/basic/display/framebuffer.py", line 158, in unpack
    allplanes = bytematrix.ByteMatrix.frompacked(
  File "pcbasic/pcbasic/basic/base/bytematrix.py", line 212, in frompacked
    for _offs in xrange(0, len(packed), width)
ValueError: range() arg 3 must not be zero

Notes

In both cases, it seems to be related to something in the EGA PlanedSpriteBuilder as the CGA PackedSpriteBuilder does not exhibit the problems (e.g. screens 1 & 2). Haven't tested Tandy.

PC-BASIC version: 2.0.3 as well as develop as of 33a20372b2499592863020159bcbb9966135e0ec. Operating system version: macOS 11.0.1

[incanus]

Running a git bisect between v2.0.2-1 (known good) and v2.0.3 for Python 2 goes through ~400 commits and points to 41fc3c7c99bebe68c4ec3f9345cb31abdc67f508 as the problem.

[robhagemans]

Cool, thanks for the bisect and the stack traces. From the trace, it looks like there's some work to do on bytematrix.

For the record, from 2.0.2 to 2.0.3 I think I replaced reams of graphics code as I was getting rid of the dependency on numpy, so it's not completely a surprise that there are some bugs there. Between EGA and CGA a different byte-packing scheme is used so that would explain why you don't see the bug in CGA.

I'll have a look at it.

[incanus]

Yes! I’ve seen the sweeping changes. I appreciate not needing numpy anymore, though.

[robhagemans]

Turns out the whole EGA sprite logic was buggy. Resolved now on develop by commits 5d186592e and 752eb51b0.