[Vm-dev] [OpenSmalltalk/opensmalltalk-vm] Incorrect literal Character encoding/decoding in SistaV1 bytecode set (Issue #618)

[Nicolas Cellier]

As reported by Marcel on Squeak-dev, this snippet:

    Compiler evaluate: (String with: $$ with: (Character value: 16r8000)).

will return a Character with a negative value (-32768).

This is because character literal in the range 16r100-16rFFFF are encoded with an extended B bytecode, and the extended B is interpreted as signed value.

I suggested
- a workaround : using `(extB bitAnd: 16rFF) << 8` to reconstruct an unsigned Character value
- a fix: using extA instead of extB so as to have it interpreted unsigned

See https://source.squeak.org/VMMakerInbox/VMMaker.oscog-nice.3174.diff for the former solution.

The later solution require more changes and a careful recompilation of CompiledMethods at image side.



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