seniorRuby
How does Ruby VM handle exception table lookup during rescue matching?
Updated May 17, 2026
Short answer
Ruby uses compiled exception tables in bytecode to quickly match rescue handlers.
Deep explanation
During compilation, Ruby builds exception tables mapping instruction ranges to rescue/ensure handlers. When an exception occurs, VM consults this table instead of scanning code dynamically. It then unwinds stack frames until a matching handler is found, executing ensure blocks along the way.
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