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Malte UblandClaude Opus 5.5
26b703a821
React Flight's production server never runs its V8 structured-stack parser
(ReactFlightStackConfigV8): every use is behind __DEV__. Builds compiled from
its sources keep that code behind `throw new Error('... should never be
called in production mode')` stubs, so scriptc lowered it, failed on
Error.prepareStackTrace, and a dead `.stack` read turned on stack-trace mode
(a frame push in every function) for the whole program.
- Statements after return/throw/break/continue in a function body are not
lowered. Declarations keep their hoisting through the existing forward
machinery (later function declarations, `var` reads undefined, `let`/
`const` TDZ); class, enum, module, import/export and generic function
declarations still lower. Functions referenced only from such code are
unreached and dead-stripped.
- Stack-trace mode requires a stack read reachable through live code
(observesStacks).
- Synchronous functions in executables push and pop their source frame
inline instead of calling scr_stack_enter/leave.
- Functions that only perform operations which never create or throw an
Error, and only call such functions, keep no frame (captureFreeFunctions):
no capture can include them.
Error.prepareStackTrace and CallSite stay refused: only development Flight
runs them. Good code is byte-identical (zero-cost gate: bench and
self-hosted compiler IR, LLVM and executables).
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>