FNIL causes segfault

[stefanberndtsson]

Running FNIL.MSA gives segfault with a rasterpos out of bounds.

$ gdb ./ostis-gdb core
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Reading symbols from ./ostis-gdb...done.
[New LWP 32001]
[New LWP 32003]
[Thread debugging using libthread_db enabled]
Using host libthread_db library "/lib/x86_64-linux-gnu/libthread_db.so.1".
Core was generated by `./ostis-gdb /var/tmp/demos/FNIL.MSA'.
Program terminated with signal SIGSEGV, Segmentation fault.
#0  0x0000000000412b02 in screen_draw (r=0, g=0, b=0) at screen.c:317
317   *rasterpos++ = r;
[Current thread is 1 (Thread 0x7fa81e90d7c0 (LWP 32001))]
(gdb) print rasterpos
$1 = 0x7fa81e8ee001 "ELF\002\001\001"
(gdb) bt
#0  0x0000000000412b02 in screen_draw (r=0, g=0, b=0) at screen.c:317
#1  0x000000000041104d in shifter_draw_high () at shifter.c:260
#2  0x00000000004112fe in shifter_clock () at shifter.c:334
#3  0x00000000004093f7 in cpu_do_cycle (cnt=12) at cpu.c:369
#4  0x0000000000409162 in cpu_step_instr (trace=0) at cpu.c:259
#5  0x000000000040930d in cpu_run (cpu_run_state=0) at cpu.c:320
#6  0x0000000000403301 in main (argc=2, argv=0x7ffd6149db78) at main.c:251
(gdb) frame 5
#5  0x000000000040930d in cpu_run (cpu_run_state=0) at cpu.c:320
320       ret = cpu_step_instr(tmp_run_state);
(gdb) print cpu->pc
$2 = 68452
(gdb) 

68452 == $10b64

No interaction is required, it crashes pretty much immediately after showing the loading screen.

[larsbrinkhoff]

It's trying to draw 501 lines, because it's in high resolution mode near the end of the screen. But there is only memory allocated for 313 lines when a colour monitor is attached.

I'm not sure how the real hardware handles this. I guess no signal is sent to RGB pins.

I think just allocating more memory is the most elegant solution. We're not trying to save RAM.

[stefanberndtsson]

Yep. Give it enough to handle all possible cases without crashing. It's better than segfaults :)

[larsbrinkhoff]

Updated with comment in the code.