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lab_t27b_ratchet: the usize scratch arrays start at zero, so the t27b interpreter reads no byte that was never written - #11136
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… interpreter reads no byte that was never written (Closes #11131) t27b test --check on the spec printed MISMATCH the_ratchet_equals_the_pythons_checker_on_every_case: jit Ok(1), interpreter Fault("8-byte read at stack+0x6ff8 of bytes never written") and 1 JIT/interpreter mismatch, which made the t27b-native-ratchet of every PR read jit/interp mismatch 1. Nine [3]usize scratch arrays were declared with no value; they are now [0, 0, 0]. After the change t27b test --check exits 0 with no mismatch (the interpreter runs 1824 runtime asserts, it stopped at 794 before) and the 14 tests pass. Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>
… interpreter reads no byte that was never written (Closes #11131) Merge of master plus sealing, gates run on the merged tree with t27c from master: tests clean with vacuous passes 0, seal --verify MATCH, tri types ratchet CLEAN, dupe_scan failure set a subset of master's. Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>
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Closes #11131
lab_t27b_ratchet: the usize scratch arrays start at zero, so the t27b interpreter reads no byte that was never written
Gates run on the merged tree (t27c from master): 1 spec(s) with tests clean and vacuous passes 0, seal --verify MATCH, tri types ratchet CLEAN, dupe_scan failure set a subset of master's (inherited red).
TEST specs/lab/lab_t27b_ratchet.t27 tests=[14] fail=[0] vacuous=[0]
SEAL specs/lab/lab_t27b_ratchet.t27 :: all hashes MATCH
TYPES RATCHET: CLEAN
DUPE failing=0 extra-vs-master=[]
Cause and measurement (issue #11131). On master,
t27b test specs/lab/lab_t27b_ratchet.t27 --checkprintedMISMATCH the_ratchet_equals_the_pythons_checker_on_every_case: jit Ok(1), interpreter Err(Fault("8-byte read at stack+0x6ff8 of bytes never written"))and1 JIT/interpreter mismatches; the interpreter had run 794 runtime asserts when it stopped. The spec declares nine[3]usizescratch arrays (sp,d,bsp,lsp,dsp) with no value; they are now[0, 0, 0]. After the change the same command exits 0 with no mismatch, the interpreter runs 1824 runtime asserts and the 14 tests pass. A probe that initialised one array at a time still mismatched for each of the nine, so the read is not in a single one; the change takes all nine.No Rust and no t27b change: the fix is in the spec, as the issue's FR-002 asks. The t27b interpreter's refusal of a read-before-write is the right behaviour and is left as it is.
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