w6c: receive sub-8 odd-sized by-value struct/array CALL return (#107)
A struct/array sized {3,5,6,7} returned by value fell past every N_LET call-receive arm (the sized-tail arm handles {1,2,4}, the memcpy arm gates on sz>8), so cstage emitted nothing and silently DROPPED the CALL — garbage exit plus a gate-blind cs!=ww divergence (wwstage emitted CALL+MOVQ via its generic let fallback). Align cstage UP: emit the CALL + one MOVQ AX, the SysV single-eightbyte receive (ref/qbe/amd64/sysv.c retr). New table-driven gate 949 (runtime exit oracle on both drivers + cs==ww byte-id; negative-control proven).
This commit is contained in:
261
test/wcc/949_oddstruct_byval_ret_run.c
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261
test/wcc/949_oddstruct_byval_ret_run.c
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/*
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* 949_oddstruct_byval_ret_run — task #107. A by-value RETURN of a
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* struct whose total size is NOT a {1,2,4,8} sized-tail width — an
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* "odd" sub-8 size 3/5/6/7 (reachable via @packed #51, and via
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* natural sub-8 maxalign-1 shapes like struct{u8,u8,u8}=3) — is a
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* single INTEGER eightbyte returned in RAX (ref/qbe/amd64/sysv.c
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* retr: the `n*8 < size` loop runs exactly once for size ≤ 8).
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*
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* Pre-#107 the cstage N_LET receive (`let r: T = mk()`) fell past
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* EVERY arm for these sizes: the whole-struct sized-tail arm excludes
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* tails {3,5,6,7}, the memcpy arm gates on sz>8, and the no-rhs
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* zero-fill requires !rhs — so cstage emitted NOTHING and SILENTLY
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* DROPPED the CALL (program exit 0, reading an uninitialised slot).
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* wwstage emitted `CALL; MOVQ AX, off(BP)` via its generic let
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* fallback (cgenstmt.ww), so the bug was BOTH a silent miscompile AND
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* a gate-blind cs≠ww divergence. The #107 fix adds a cstage arm that
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* mirrors wwstage's single-MOVQ receive: the producer zero-pads AX to
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* 24B and localslot rounds every slot up to 8B, so one full-word MOVQ
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* captures the eightbyte cleanly.
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*
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* GATE POLARITY: must stay GREEN. Two independent oracles per row:
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* - the runtime exit code (the load-bearing oracle: byte-id is BLIND
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* to a both-wrong-identical pair, and pre-#107 cstage's drop was
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* exit-0 — a green runtime here proves the CALL fires and the
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* value reaches the caller, on BOTH stage drivers).
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* - w6c vs w6c_ww .s byte-identity (rule 10).
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*
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* The expected exit is the value of the RETURNED field, COMPUTED in
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* the row table (no derived size literals; the field value is the
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* oracle, not a layout number) and pinned at 0..255.
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*
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* Size coverage targets the gap the bug lived in plus boundaries:
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* 3 — struct{u8,u8,u8}, natural maxalign-1, sub-8 odd
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* 5 — @packed{u8,u32}, sub-8 odd, field b crosses byte 1..4
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* 6 — struct{u16,u16,u16}, sub-8 odd, field c at byte 4
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* 7 — @packed{u8,u16,u32}, sub-8 odd, field c at byte 3..6
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* 8 — struct{i32,i32}, boundary: single full eightbyte
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* 12 — struct{i32,i32,i32}, >8 two-eightbyte (sized MOVL tail)
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* 24 — struct{i64,i64,i64}, three-eightbyte, top of register ABI
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* The 8/12/24 rows lock that the #107 arm did NOT perturb the existing
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* sized-tail / multi-word receive paths.
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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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/* size 3: natural maxalign-1, return first field (byte 0). */
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{ "s3_u8x3_fieldA",
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"package main;\n"
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"type T = struct { a: u8, b: u8, c: u8 };\n"
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"fn mk() T = { return T { a = 116u8, b = 22u8, c = 33u8 }; };\n"
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"export fn main() i32 = { let r: T = mk(); return r.a: i32; };\n",
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116 },
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/* size 5 (@packed{u8,u32}): return field b (bytes 1..4) — proves the
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* whole eightbyte, not just AX's low byte, reaches the caller. */
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{ "s5_packed_fieldB",
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"package main;\n"
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"type T = struct @packed { a: u8, b: u32 };\n"
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"fn mk() T = { return T { a = 9u8, b = 116u32 }; };\n"
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"export fn main() i32 = { let r: T = mk(); return r.b: i32; };\n",
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116 },
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/* size 6 (3x u16): return field c (bytes 4..5). */
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{ "s6_u16x3_fieldC",
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"package main;\n"
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"type T = struct { a: u16, b: u16, c: u16 };\n"
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"fn mk() T = { return T { a = 9u16, b = 22u16, c = 116u16 }; };\n"
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"export fn main() i32 = { let r: T = mk(); return r.c: i32; };\n",
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116 },
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/* size 7 (@packed{u8,u16,u32}): return field c (bytes 3..6). */
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{ "s7_packed_fieldC",
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"package main;\n"
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"type T = struct @packed { a: u8, b: u16, c: u32 };\n"
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"fn mk() T = { return T { a = 9u8, b = 22u16, c = 116u32 }; };\n"
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"export fn main() i32 = { let r: T = mk(); return r.c: i32; };\n",
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116 },
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/* size 8 boundary: single full eightbyte, return first field. */
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{ "s8_i32x2_fieldA",
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"package main;\n"
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"type T = struct { a: i32, b: i32 };\n"
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"fn mk() T = { return T { a = 116, b = 22 }; };\n"
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"export fn main() i32 = { let r: T = mk(); return r.a; };\n",
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116 },
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/* size 12: two eightbytes (MOVQ + MOVL tail) — unchanged by #107. */
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{ "s12_i32x3_fieldC",
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"package main;\n"
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"type T = struct { a: i32, b: i32, c: i32 };\n"
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"fn mk() T = { return T { a = 9, b = 22, c = 116 }; };\n"
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"export fn main() i32 = { let r: T = mk(); return r.c; };\n",
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116 },
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/* size 24: three eightbytes, top of the register-return ABI. */
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{ "s24_i64x3_fieldC",
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"package main;\n"
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"type T = struct { a: i64, b: i64, c: i64 };\n"
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"fn mk() T = { return T { a = 9i64, b = 22i64, c = 116i64 }; };\n"
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"export fn main() i32 = { let r: T = mk(); return r.c: i32; };\n",
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116 },
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};
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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/oddret_%d_%d.ww", getpid(), i);
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snprintf(tmpdir, sizeof tmpdir, "/tmp/oddret_%d_d_%d", getpid(), i);
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FILE *f = fopen(src, "wb");
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if (!f) return -2;
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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 && timeout 180 %s build %s 2>/dev/null",
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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 -2;
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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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/* w6c (cstage) vs w6c_ww (wwstage) .s byte-id (rule 10). */
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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/oddret_asm_%d_%d.ww", getpid(), i);
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snprintf(cs, sizeof cs, "/tmp/oddret_asm_%d_%d_c.s", getpid(), i);
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snprintf(ws, sizeof ws, "/tmp/oddret_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, "timeout 180 %s/w6c -o %s %s 2>/dev/null",
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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, "timeout 180 %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], wdrv[1024];
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snprintf(cdrv, sizeof cdrv, "%s/ww", bin);
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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; }
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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 && access(drivers[d].path, X_OK) != 0) {
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fprintf(stderr, "oddstruct_byval_ret: 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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"oddstruct_byval_ret[%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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"oddstruct_byval_ret: %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("oddstruct_byval_ret: %d/%d ok\n", total, total);
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return 0;
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}
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