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Bug #411

open

AOZ sometimes scrambles code order.

Added by Brian Flanagan about 4 years ago. Updated about 4 years ago.

Status:
New
Priority:
Low
Target version:
-
Start date:
07/13/2020
Due date:
% Done:

0%

Estimated time:
4:00 h
Affected version:

Description

Example: Given the following code:

End

  //----------------------------|
 // Initialize Apple 2 Emulator |
//------------------------------|
A2M_Init:
Print "Loading ROM!!!"
    Gosub Load_ROM          ' Load ROM image from file.
Print "Loading Memory"
    Gosub Load_Memory       ' Eventually, will load RAM image from file.  Right now, just allocates the memory.
Print "Relocating ROM<<<"
    Gosub Relocate_ROM      ' later on won't want to do this, since extended memory 16K memory card will be bank-switched
                            ' with ROM.  We'll want to re-code for this eventuality.
Print "Resetting registers."
    Gosub Reset_Registers   ' Initialize 6502 registers
Print "Setting Reset Vector"
    PC = $FA62              ' Reset Vector address.
Return

The following instruction is executed:
Gosub A2M_Init
The result is very weird:

Relocating ROM<<<
Loading ROM!!!
Resetting Registers.
$E8D4A51000

What we should see:
Loading ROM!!!
Load_ROM:

(...because there was an End in Load_ROM)
Even if we ignore this, we should then see the following:

Loading Memory
Relocating ROM<<<
Resetting Registers.
Setting Reset Vector

...but they're all scrambled.
First of all, the code inside Load_ROM is being ignored.
It's also apparent that the statements are being executed out of order... seemingly at random.  
I put the symbols <<< and !!! at the end of the statements to ensure that was the actual code being called.
The last item (a hexidecimal number) isn't even in this block of code!!!
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