Hojun-Cho
83f5956df2
Every section banner dies (103 -> 0) across test/lang, the observer suites, the C carriers, and the five comment-heavy corpus fixtures; banner provenance (#N cites, carrier numbers, repair-cluster labels) folded into headers or adjacent WHY comments. Narration deleted; row provenance, ref cites, divergence pins, and layout contracts kept (fwd-ref decl-order guards and bootstrap-gate corpus rationale restored where the sweep over-cut). Comment-only proven: all 3742 wwbuild workdir .s byte-identical before/after; test-commit and test-byteid (161 lang + 1399 data, 0 pinned-divergent) green.
44 lines
1.9 KiB
Plaintext
44 lines
1.9 KiB
Plaintext
// Runtime contract for a whole 24B str header
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// produced by an UNWRAP source (`mk_se()!` N_TRYUNW) passed BY VALUE as a
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// call argument. #6 (Mechanism A): cgenutil.ww's nodeisstr had no
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// N_TRYUNW/N_TRYPROP arm, so the unwrap fell through to the scalar
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// single-PUSHQ default — pushargsrev marshalled only .ptr (1 word) and
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// cgcall's pop sizer drained one word, so the callee read .len/.cap from
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// stale arg registers. cstage (cmd/w6c/cgen.c node_isstr) was always
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// type-keyed and correct; this aligns wwstage UP. Twin of #9's
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// deref_callarg str pin — same masking mechanism, different node kind.
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//
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// WHY the poison call: a pre-fix `strlen(mk_se()!)` pushes only .ptr, so
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// the callee reads .len from whatever arg register the caller left. The
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// preceding NORMAL-arg call strlen(decoy) deterministically leaves the
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// callee's .len register holding decoy's len 2 (≠ backing's 5), so a
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// pre-fix 1-word push reads 2 and the assert REDDENS. This is a wwstage-
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// only gap (cs≠ww), so the tooth is byte-id (cstage already pushed 3) AND
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// value-under-the-wwstage-frontend; byte-id (990-996) proves the stages
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// AGREE, not that the code is correct.
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package unwrap_callarg_str_test;
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type e = !i32;
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fn mk_se() (str | e) = { return "abcde"; };
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fn strlen(s: str) i32 = { return s.len: i32; };
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fn strcap(s: str) i32 = { return s.cap: i32; };
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fn strfirst(s: str) i32 = { return s[0]: i32; };
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@test fn str_unwrap_callarg() void = {
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// Decoy ("xy", len 2) poisons the callee's .len register via a
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// normal-arg call; the unwrap-source call must overwrite it with 5.
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let decoy: str = "xy";
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assert(strlen(decoy) == 2);
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assert(strlen(mk_se()!) == 5);
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// .cap is the 3rd dropped word; decoy ("xy") seeds cap 2, so a
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// pre-fix 1-word push leaves the callee reading 2 here, not 5.
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assert(strcap(mk_se()!) == 5);
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// strfirst pins .ptr survived the push ('a' == 97).
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assert(strfirst(mk_se()!) == 97);
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};
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