cstage+selfhost+test: fix (*p).f silent drop in N_DOT lhs (read+write)
Pre-existing landmine surfaced by #5 (whole-STRUCT N_ASSIGN). Both stages' N_DOT dispatch gated on `lhs->lhs->kind == N_IDENT`; the parser produces N_UN(STAR, IDENT(p)) for `(*p).f`, so both sides fell off: - Write side (cgassign N_DOT base): emitted nothing, store dropped. - Read side (case N_DOT pointer-auto-deref): cgexpr derefed the pointer as a scalar, AX = first qword of struct, field offset dropped. Fix: retarget base / dot_lhs to the inner IDENT when shape is N_UN(STAR, IDENT). The existing via_ptr branch fires identically to `p.f`. v1 scope is bare-IDENT inner only; `(*expr).f` (non-IDENT pointer expression) is tracked separately as task #19. 702 covers 7 rows: write_i64/i32/str, read_i64/i32/str_len, roundtrip
This commit is contained in:
297
test/wcc/702_dot_explicit_deref.c
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297
test/wcc/702_dot_explicit_deref.c
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/*
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* 702_dot_explicit_deref — silent miscompile of `(*p).f` (task #16).
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*
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* Pre-existing landmine surfaced by worker-cgnassign during #5
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* (whole-struct N_ASSIGN). Both cstage cgen.c N_ASSIGN N_DOT and
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* wwstage cgenexpr.ww cgassign single-dot dispatch gated on
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* `n->lhs->lhs->kind == N_IDENT`. The parser produces N_UN(STAR,
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* IDENT(p)) for `(*p).f`, so the store fell off the dispatch and
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* silently emitted nothing. Read-side N_DOT had the same gap —
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* the pointer-auto-deref load branch required N_IDENT and fell
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* through to cgexpr on the N_UN, which derefs the pointer as a
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* scalar (load 8B from p into AX, then the field part is dropped).
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*
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* Not exercised by current selfhost source (auto-deref `p.f` was
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* used throughout) so 995_self_rebuild didn't catch it. Latent for
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* any future user code that types out the explicit deref.
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*
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* The fix in both stages is a base/lhs retarget: when the parser
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* shape is N_UN(STAR, IDENT(p)), substitute the inner IDENT so
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* the existing via_ptr / pointer-auto-deref branch fires the same
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* as `p.f`. v1 scope is bare-IDENT inner only; `(*expr).f` with a
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* non-IDENT pointer expression (`(*arr[i]).f`, `(*g.p).f`) still
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* drops silently, tracked as a follow-up — needs cgexpr(inner) →
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* reg + RHS-spill scheduling, which is a different design.
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*
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* Each row pins:
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* - cstage value correctness (process exit code).
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* - wwstage value correctness (when ww_ww exists).
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* - cstage vs wwstage byte-identical .s output (catches drift).
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*/
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#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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#include <unistd.h>
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#include <sys/stat.h>
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#include <sys/wait.h>
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static int
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runwait(const char *cmd)
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{
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int rc = system(cmd);
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if (rc == -1) return -1;
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if (WIFEXITED(rc)) return WEXITSTATUS(rc);
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return -1;
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}
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struct row { const char *label; const char *src; int want; };
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static const struct row rows[] = {
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/* Write side, scalar i64 field via explicit deref.
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* Pre-fix: cgassign single-dot dispatch fell off (base.kind
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* was N_UN, not N_IDENT) and emitted no store. f stayed 0. */
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{ "write_i64",
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"type pt = struct { x: i64, y: i64 };\n"
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"fn main() i32 = {\n"
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" let s: pt = pt { x = 0i64, y = 0i64 };\n"
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" let p: *pt = &s;\n"
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" (*p).x = 7i64;\n"
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" (*p).y = 35i64;\n"
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" return (s.x + s.y): i32;\n"
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"};\n",
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42 },
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/* Write side, narrow i32 field. Pins fldstoreop sizing on
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* the via_ptr path — MOVL not MOVQ (which would stomp 4 bytes
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* past the field). */
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{ "write_i32",
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"type box = struct { a: i32, b: i32, c: i32 };\n"
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"fn main() i32 = {\n"
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" let s: box = box { a = 0, b = 0, c = 0 };\n"
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" let p: *box = &s;\n"
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" (*p).a = 5;\n"
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" (*p).b = 11;\n"
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" (*p).c = 19;\n"
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" return s.a + s.b + s.c;\n"
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"};\n",
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35 },
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/* Write side, str field. Pins the str-typed field branch in
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* the via_ptr path (cgexpr → AX=ptr/BX=len, store both halves
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* at +0/+8 — not just AX). Initialiser uses `let v: box;`
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* (zero-fill) instead of a struct literal because N_LET
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* N_STRUCTLIT silently drops the .len half of a str-typed
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* field — a separate pre-existing bug, out of scope here. */
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{ "write_str",
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"type box = struct { s: str, n: i64 };\n"
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"fn main() i32 = {\n"
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" let v: box;\n"
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" let p: *box = &v;\n"
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" (*p).s = \"hi\";\n"
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" (*p).n = 40i64;\n"
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" return (v.s.len: i64 + v.n): i32;\n"
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"};\n",
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42 },
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/* Read side, scalar i64 field via explicit deref.
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* Pre-fix: case N_DOT's pointer-auto-deref branch required
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* N_IDENT and fell through to `cgexpr(c, n->lhs, ...)` —
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* derefed the pointer as if loading a scalar, so AX held the
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* first qword of the struct (s.x = 50). Field offset for .y
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* (+8) was dropped → returned 50 instead of 80. */
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{ "read_i64",
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"type pt = struct { x: i64, y: i64 };\n"
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"fn main() i32 = {\n"
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" let s: pt = pt { x = 50i64, y = 80i64 };\n"
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" let p: *pt = &s;\n"
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" return (*p).y: i32;\n"
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"};\n",
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80 },
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/* Read side, narrow i32 field. Pins fldloadop sizing — MOVL
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* with sign-extend, not raw MOVQ. */
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{ "read_i32",
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"type box = struct { a: i32, b: i32, c: i32 };\n"
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"fn main() i32 = {\n"
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" let s: box = box { a = 1, b = 2, c = 3 };\n"
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" let p: *box = &s;\n"
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" return (*p).a + (*p).b + (*p).c;\n"
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"};\n",
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6 },
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/* Read side, str field. Pins the str-typed field load path —
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* AX=ptr, BX=len. .len is the receive-side check. Initialiser
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* uses write-by-field (same str-in-structlit-init bug avoided
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* as in write_str). */
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{ "read_str_len",
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"type box = struct { s: str };\n"
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"fn main() i32 = {\n"
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" let v: box;\n"
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" v.s = \"hello\";\n"
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" let p: *box = &v;\n"
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" return (*p).s.len: i32;\n"
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"};\n",
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5 },
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/* Mixed: write via (*p).f then read via (*p).f. End-to-end
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* round-trip pins both sides agreeing on the same offset and
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* width. */
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{ "roundtrip",
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"type pt = struct { x: i32, y: i32, z: i32 };\n"
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"fn main() i32 = {\n"
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" let s: pt = pt { x = 0, y = 0, z = 0 };\n"
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" let p: *pt = &s;\n"
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" (*p).x = 4;\n"
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" (*p).y = 7;\n"
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" (*p).z = 13;\n"
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" return (*p).x + (*p).y + (*p).z;\n"
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"};\n",
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24 },
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};
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/* run_driver — compile r->src via the given driver and exec; return
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* the process exit code. Mirror of 701's helper. */
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static int
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run_driver(const char *driver, const struct row *r, int i)
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{
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char src[64], tmpdir[64], cmd[1024];
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snprintf(src, sizeof src, "/tmp/wded_%d_%d.ww", getpid(), i);
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snprintf(tmpdir, sizeof tmpdir, "/tmp/wded_%d_d_%d", getpid(), i);
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FILE *f = fopen(src, "wb");
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if (!f) return -1;
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fputs(r->src, f);
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fclose(f);
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mkdir(tmpdir, 0755);
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snprintf(cmd, sizeof cmd, "cd %s && %s build %s",
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tmpdir, driver, src);
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if (runwait(cmd) != 0) {
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fprintf(stderr, "row[%s]: build via %s failed\n",
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r->label, driver);
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unlink(src); rmdir(tmpdir);
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return -1;
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}
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const char *base = strrchr(src, '/');
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base = base ? base + 1 : src;
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char outbin[128];
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snprintf(outbin, sizeof outbin, "%s/%s", tmpdir, base);
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char *dot = strrchr(outbin, '.');
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if (dot && strcmp(dot, ".ww") == 0) *dot = '\0';
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int got = runwait(outbin);
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unlink(src); unlink(outbin); rmdir(tmpdir);
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return got;
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}
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/* asm_byte_identical — generate .s via cstage's w6c and wwstage's
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* w6c_ww and diff. Mirror of 701. */
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static int
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asm_byte_identical(const char *bin, const struct row *r, int i)
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{
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char src[64], cs[64], ws[64], cmd[1024];
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snprintf(src, sizeof src, "/tmp/wded_asm_%d_%d.ww", getpid(), i);
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snprintf(cs, sizeof cs, "/tmp/wded_asm_%d_%d_c.s", getpid(), i);
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snprintf(ws, sizeof ws, "/tmp/wded_asm_%d_%d_w.s", getpid(), i);
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FILE *f = fopen(src, "wb");
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if (!f) return -1;
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fputs(r->src, f);
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fclose(f);
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snprintf(cmd, sizeof cmd, "%s/w6c -o %s %s 2>/dev/null", bin, cs, src);
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if (runwait(cmd) != 0) {
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fprintf(stderr, "row[%s]: w6c errored\n", r->label);
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unlink(src);
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return -1;
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}
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snprintf(cmd, sizeof cmd, "%s/w6c_ww -o %s %s 2>/dev/null",
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bin, ws, src);
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if (runwait(cmd) != 0) {
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fprintf(stderr, "row[%s]: w6c_ww errored\n", r->label);
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unlink(src); unlink(cs);
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return -1;
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}
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FILE *fc = fopen(cs, "rb");
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FILE *fw = fopen(ws, "rb");
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int rc = 0;
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if (!fc || !fw) {
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rc = -1;
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} else {
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for (;;) {
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int a = fgetc(fc);
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int b = fgetc(fw);
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if (a != b) { rc = -1; break; }
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if (a == EOF) break;
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}
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}
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if (fc) fclose(fc);
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if (fw) fclose(fw);
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if (rc != 0)
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fprintf(stderr, "row[%s]: cstage vs wwstage asm differs\n",
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r->label);
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unlink(src); unlink(cs); unlink(ws);
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return rc;
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}
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int
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main(void)
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{
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const char *bin = getenv("BIN");
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if (!bin) bin = "out/bin";
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char absbin[1024];
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if (bin[0] != '/') {
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char cwd[1024];
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if (getcwd(cwd, sizeof cwd) == NULL) return 1;
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snprintf(absbin, sizeof absbin, "%s/%s", cwd, bin);
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bin = absbin;
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}
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char cdrv[1024];
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snprintf(cdrv, sizeof cdrv, "%s/ww", bin);
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char wdrv[1024];
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snprintf(wdrv, sizeof wdrv, "%s/ww_ww", bin);
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struct { const char *name; const char *path; int gated_on_existence; }
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drivers[] = {
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{ "cstage", cdrv, 0 },
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{ "wwstage", wdrv, 1 },
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{ NULL, NULL, 0 },
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};
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int n = (int)(sizeof rows / sizeof rows[0]);
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int total = 0, fail = 0;
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for (int d = 0; drivers[d].name; d++) {
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if (drivers[d].gated_on_existence
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&& access(drivers[d].path, X_OK) != 0) {
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fprintf(stderr, "dot_explicit_deref: skip %s (no %s)\n",
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drivers[d].name, drivers[d].path);
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continue;
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}
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for (int i = 0; i < n; i++) {
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int got = run_driver(drivers[d].path, &rows[i], i);
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total++;
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if (got != rows[i].want) {
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fprintf(stderr,
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"dot_explicit_deref[%s][%s]: exit=%d want=%d\n",
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drivers[d].name, rows[i].label,
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got, rows[i].want);
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fail++;
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}
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}
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}
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if (access(wdrv, X_OK) == 0) {
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for (int i = 0; i < n; i++) {
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total++;
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if (asm_byte_identical(bin, &rows[i], i) != 0)
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fail++;
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}
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}
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if (fail) {
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fprintf(stderr,
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"dot_explicit_deref: %d/%d fixtures failed\n",
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fail, total);
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return 1;
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}
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printf("dot_explicit_deref: %d/%d ok\n", total, total);
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return 0;
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}
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