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fix(gen-c): a _ switch arm is the catch-all, not (x == _) (Closes #7428) - #7456
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gen-c lowers a switch to a chain of ternaries ending in the else value. The arm `_ =>` is the same catch-all and was written as the comparison `(x == _)`, which C rejects. The test in backend_behaviour.rs compiles and runs the C for an integer and an enum switch. Part of #5980. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Only gen_hash_c moves: the `== _` arms become the catch-all value. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
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t27c: refuse a malformed number literal by name, read 0o as octal (Closes #7319, Closes #2645)
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…w lowers it as the catch-all (Closes #7879) (#7880) #7331 dropped the switch fixture's `_ =>` arm (43dbe54) because gen-c then wrote `(x == _)` for it, which C cannot compile. #7456 made `_` the catch-all, so `rest()` and its two asserts come back unchanged and the `_` catch-all is built and run, not only accepted. On the t27c lab (master ce605a6 with #7436): gen-c of the fixture has no `(x == _)`, and `cargo test --release -p t27c --test core_selfhost` passes 1/1. Co-authored-by: Claude <claude@anthropic.com> Co-authored-by: Claude Opus 5.5 <noreply@anthropic.com>
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Closes #7428
Part of #5980
What was wrong
gen-c lowers a switch expression to a chain of ternaries, and the
elsearm becomes the value at the end of the chain._ =>is the same catch-all, but gen-c wrote it as the comparison(x == _). C rejects that:'_' undeclared.The fix
bootstrap/src/compiler.rs: an arm named_is treated likeelse(+4/-1).Test
bootstrap/tests/backend_behaviour.rs, new testc_takes_the_underscore_arm_of_a_switch(+15). It generates C for an integer switch and an enum switch, compiles it with cc, runs it, and checks the output10 99 1 7.Run on the t27c lab with
try.sh, both ways:backend_behaviour23 passedcompiler.rsandFROZEN_HASHreverted to master: 22 passed, 1 failed (this test; cc refuses the C)Reseals
The corpus gen-c diff, old binary vs new over every spec under
specs/plus the 28 sealed specs outside it, changes exactly one file:specs/demos/jones_topology_decision_gate.t27. Its== _arms become the catch-all value. That spec is resealed, together with its twin seal:JonesTopologyDecisionGate.jsonanddemos_JonesTopologyDecisionGate.json. Onlygen_hash_c(db1eb4ba -> f692906e) and the bookkeeping fields move. No other seal goes stale.Budget
check_budget()from master (#7371) passes: compiler.rs +4, backend_behaviour.rs +15, 19 in total. Both files are already listed intools/policy/foreign-exceptions.txton master, so this PR does not touch that file.🤖 Generated with Claude Code