BBC Basic bug from <checks> 1987

I raised a ticket for this because it’s as serious as it gets. Turns out the whole-array manipulation is even more wonky than I thought.

If, during whole-array maths (eg a()=b/c()) there’s any kind of error – overflow, divide by zero, etc – the interpreter will corrupt its own memory, potentially fatally.

I thought it was merely corrupting its own error report string, but no, it accidentally overwrites variable memory and so can permanently break a variable chain, with fatal results. [And if it’s a LOCAL array, it can overwrite the stack – good luck with that]

It’s the usual problem – the interpreter relies on R8 so if you use R8 for something else, the rest of the interpreter can’t work. The bug is in ten places in the array code, so fixing the error handler is easiest – one extra instruction.

I think ROOL might be ahead of you on this one. This sounds like the Basic bug which was recently fixed.