wcc/cgen: #52 error-first tagged-union success tag — successtag helper not hardcoded 0 (wwstage)
An error-first tagged union -- error variant at tag 0, success at tag 1+, e.g. (myerr | u16) -- was silently miscompiled by wwstage: the try/propagate codegen hardcoded success = tag 0, so the actual success value (tag 1) failed the CMPQ $0 and fell to the error path -> exit(1) instead of the value (44). cstage was correct (computes the success tag via cg_tagged_success_tag = first non-error variant). wwstage-only: a successtag/successvariant helper (mirroring cstage) replaces the hardcoded tag-0 / first-param assumption at all four try sites -- cgtryprop (?), cgtryunw (!), and the two latent shift sites cgtrytupleshift + cgtrytaggedshift (which bite an error-first union with an aggregate success payload). Success-first unions (the Hare idiom + what the selfhost uses) keep successtag=0 -> CMPQ $0 unchanged -> byte-id-neutral on 990-997. cstage untouched (w6c md5 unchanged). byte-id 990-997 8/8. test/wcc/825 table-driven (errfirst must/prop + tuple-success + success-first control). A separate nested-tagged-union construction divergence is filed (#10/#125).
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279
test/wcc/825_errfirst_union_try.c
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279
test/wcc/825_errfirst_union_try.c
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/*
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* 825_errfirst_union_try — error-first tagged-union try (`?`/`!`) success-tag
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* (#52, the #216 deferred divergence). wwstage HARDCODED the success tag as 0,
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* so for an ERROR-FIRST union — error variant at tag 0, success at tag 1+ (e.g.
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* `(e | u16)` with `type e = !i32`) — the success (tag 1) failed the `CMPQ $0`
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* success check and fell to the error path: `!` → exit(1), `?` → propagate.
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* cstage was already correct via cg_tagged_success_tag (cmd/w6c/cgen.c:857):
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* if any variant is an error, the success tag is the first NON-error variant's
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* index, else 0. The `.s` diff was literally `CMPQ $1` (cstage) vs `CMPQ $0`
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* (wwstage).
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*
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* The fix (selfhost cgenexpr.ww only — cstage UNCHANGED): a `successtag`
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* helper mirroring cstage's, applied at the FOUR sites that shared the tag-0 /
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* first-param assumption — cgtryprop CMPQ, cgtryunw CMPQ, and the
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* cgtrytupleshift / cgtrytaggedshift payload-variant lookups (successvariant).
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*
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* row | shape | want
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* ----------------+----------------------------------------+------
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* errfirst_must | (e|u16) `!` unwrap (THE repro) | 44
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* errfirst_prop | (e|u16) `?` propagate through outer fn | 44
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* succfirst_ctrl | (u16|e) `!` — successtag=0, CMPQ $0 | 7
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* errfirst_3var | (e1|e2|u16) success at index 2 | 99
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* errfirst_tuple | (e|(u16,u16)) `!` — successvariant shift| 51
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*
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* errfirst_tuple is the LATENT-site row: the cgtrytupleshift payload-shift only
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* bites an error-first union whose SUCCESS variant is itself a tuple. Pre-fix it
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* fell two ways — the CMPQ $0 rejected tag-1 (→ exit 1), AND even with the CMPQ
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* fixed the shift read ou.params.type_ (the error variant, not a tuple) so the
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* rvalue tuple never filled the cursor (verified mutation: 88, not 51). The
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* successvariant fix routes the shift to the tuple. The sibling cgtrytaggedshift
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* (nested-tagged success) shares the identical successvariant call; it is not
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* exercised here because nested-tagged union *construction* (the return-coercion
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* box, main.ok) has a separate pre-existing cs!=ww divergence — #52-independent
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* (present success-first too) — filed for its own fix.
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*
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* Exit codes are the process low-8-bits: 300 & 0xFF = 44. errfirst_* are the
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* mutation-sane rows: pre-fix wwstage = exit 1 (wrong-tag → error path),
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* cstage = correct → cs!=ww. succfirst_ctrl is the byte-id no-regress guard:
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* successtag returns 0 there, so its `CMPQ $0` is UNCHANGED. A byte-id pass
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* pins cstage==wwstage `.s` for every row.
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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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/* errfirst_must — THE repro: error-first `(e|u16)`, `!` unwrap of a
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* tag-1 success. Pre-fix wwstage CMPQ $0 vs tag 1 → error → exit 1. */
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{ "errfirst_must",
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"package main;\n"
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"type e = !i32;\n"
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"type u = (e | u16);\n"
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"fn ok() u = { return 300u16; };\n"
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"export fn main() i32 = {\n"
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"\tlet x = ok()!;\n"
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"\treturn x: i32;\n"
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"};\n",
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44 },
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/* errfirst_prop — the `?` twin: outer propagates inner's success
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* through the same error-first union, then `!` unwraps. */
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{ "errfirst_prop",
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"package main;\n"
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"type e = !i32;\n"
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"type u = (e | u16);\n"
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"fn inner() u = { return 300u16; };\n"
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"fn outer() u = {\n"
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"\tlet v = inner()?;\n"
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"\treturn v;\n"
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"};\n"
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"export fn main() i32 = {\n"
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"\treturn outer()!: i32;\n"
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"};\n",
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44 },
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/* succfirst_ctrl — success-FIRST `(u16|e)`, successtag=0: the byte-id
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* no-regress guard, CMPQ $0 unchanged. */
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{ "succfirst_ctrl",
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"package main;\n"
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"type e = !i32;\n"
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"type u2 = (u16 | e);\n"
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"fn g() u2 = { return 7u16; };\n"
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"export fn main() i32 = {\n"
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"\treturn g()!: i32;\n"
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"};\n",
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7 },
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/* errfirst_3var — two error variants then success: successtag walks
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* past index 0 AND 1 to return 2, pinning the walk (not 0, not 1). */
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{ "errfirst_3var",
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"package main;\n"
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"type e1 = !i32;\n"
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"type e2 = !i64;\n"
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"type u3 = (e1 | e2 | u16);\n"
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"fn h() u3 = { return 99u16; };\n"
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"export fn main() i32 = {\n"
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"\treturn h()!: i32;\n"
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"};\n",
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99 },
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/* errfirst_tuple — error-first union whose SUCCESS variant is a tuple:
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* exercises cgtrytupleshift via successvariant. Pre-fix exit 1 (CMPQ $0
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* rejects tag 1); CMPQ-fixed-but-shift-reverted gives 88; full fix → 51
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* (300+7 = 307, 307 & 0xFF = 51). */
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{ "errfirst_tuple",
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"package main;\n"
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"type e = !i32;\n"
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"type ut = (e | (u16, u16));\n"
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"fn ok() ut = { return (300u16, 7u16); };\n"
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"export fn main() i32 = {\n"
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"\tlet t = ok()!;\n"
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"\tlet (a, b) = t;\n"
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"\treturn (a: i32) + (b: i32);\n"
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"};\n",
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51 },
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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/efu_%d_%d.ww", getpid(), i);
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snprintf(tmpdir, sizeof tmpdir, "/tmp/efu_%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 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 -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 — w6c vs w6c_ww .s for the same source must match. */
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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/efu_asm_%d_%d.ww", getpid(), i);
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snprintf(cs, sizeof cs, "/tmp/efu_asm_%d_%d_c.s", getpid(), i);
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snprintf(ws, sizeof ws, "/tmp/efu_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, "errfirst_union_try: 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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"errfirst_union_try[%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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"errfirst_union_try: %d/%d fixtures failed\n", fail, total);
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return 1;
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}
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printf("errfirst_union_try: %d/%d ok\n", total, total);
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return 0;
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}
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