Pokemon Emerald: Fix terra/marine caves bugged internal id #3161
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In the previous version of this PR before the force push I lost my mind for a moment and forgot that 4 bits can hold values 0-15 and not just values 0-7. It's only this one marine cave id that can trigger the problem. |
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Berserker66
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Apr 18, 2024
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What is this fixing or adding?
Terra and Marine Cave have 8 possible locations each with mutually exclusive internal location ids 1-16. Location id 0 means "no abnormal weather", hence starting at 1. But that means a possible value of 16 would require 5 bits, which is larger than the allotted size in the ROM of 4 bits.
I believe this results in a 1/8 chance that Kyogre is not findable, but nobody has reported that behavior. This was found while using #2995, which crashes when
struct.packis asked to fill a byte with a number that requires 9 bits to store.How was this tested?
Generated with a check in
_set_bytes_leif the value was ever larger than the specified size until I hit the condition. Tried again with the same seed on this branch and it didn't fail. Though I suppose changing the size of the array it picks from affects RNG. Generating a few 20-player multis also didn't encounter the issue with the size check, which should happen 1/8 times.