gen-c: an un-annotated local takes its type from the initialiser (Refs #2161) - #2734
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…#2161) The fallback for a local with no declared type was C's `int`. Two arms above it already special-case integer literals (u32/u64), so what the fallback actually caught was everything else -- a CALL among them: pub fn big() -> u64 { return 4294967296; } pub fn plus_one() -> u64 { const v = big(); // int v = big(); return v + 1; } C prints 1. Rust and Zig print 4294967297. The C compiles without a diagnostic, so nothing downstream can tell -- a silent wrong answer, which is worse than a loud one. Now GNU `__auto_type` when there is an initialiser, which is the same builtin the tuple-destructure paths a few hundred lines above already emit, so it costs no new portability. Without an initialiser there is nothing for it to follow and `int` stays. Measured over 746 tracked specs, before binary vs after: specs whose C output changes 396 cc -fsyntax-only -std=gnu11 errors 6163 -> 5958 specs whose generated C is clean 19 -> 20 specs that went clean -> broken 0 That last row is the one that matters at this radius. Parse count 620/746 and tests 1629 passed / 6 failed are both unchanged. The probe now agrees across backends: C prints 4294967297, same as Rust. FROZEN_HASH resealed in the same commit (M5).
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The fallback for a local with no declared type was C's
int. Two arms above it already special-case integer literals (u32/u64), so what the fallback actually caught was everything else — a call among them:C prints 1. Rust and Zig print 4294967297. The C compiles without a diagnostic, so nothing downstream can tell — a silent wrong answer, which is worse than a loud one.
Now GNU
__auto_typewhen there is an initialiser — the same builtin the tuple-destructure paths a few hundred lines above already emit, so it costs no new portability. Without an initialiser there is nothing for it to follow andintstays.Measured over 746 tracked specs
cc -fsyntax-only -std=gnu11errorsThat last row is the one that matters at this radius. Counting only the totals would have hidden a swap — two fixed and one broken looks the same as one fixed in a sum.
Parse count 620/746 and tests 1629 passed / 6 failed are both unchanged.
The probe now agrees across backends: C prints 4294967297, same as Rust.
Refs #2161