Hojun-Cho
1752305be7
The one-sided guard `v > 214748364` never fired for the last digit: at v==214748364 a next digit of '8'/'9' made `v*10+digit` overflow i32 and wrap negative, slipping past the signed args-index bound check at fmt.ww:703 -> OOB arg read -> SIGSEGV on any format directive carrying an over-i32 digit run (index, width or precision). Complete it to the canonical two-part pre-multiply Horner guard (MAX/10, MAX%10). Hand-rolled in signed i32, not Hare scan_sz's unsigned post-multiply wrap-check (ref/hare/strconv/stou.ha:60), which would be signed-overflow UB-class here; noted at the site. Table-driven subprocess test over all three scandigits call sites, 5 rows x both stages; reverting the guard reproduces exit=139.
236 lines
7.1 KiB
C
236 lines
7.1 KiB
C
/*
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* 989_fmt_scanoverflow_run — drain item F-A: lib/fmt scandigits dropped
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* the last-digit overflow case.
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*
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* scandigits (lib/fmt/fmt.ww) accumulates a format-directive digit run
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* into an i32 with a Horner loop. The guard was a one-sided
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* `if (v > 214748364)`, which never fires when v == 214748364 and the
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* next digit is '8' or '9': v * 10 + 8/9 = 2147483648/2147483649
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* overflows i32 and wraps NEGATIVE. A negative explicit arg index then
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* slips past the signed `idx >= args.len` guard in fprintf (fmt.ww:703)
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* and `args[idx]` reads far out of bounds -> SIGSEGV.
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*
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* The fix completes the canonical Horner pre-multiply guard to the
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* two-part form `v > MAX/10 || (v == MAX/10 && digit > MAX%10)`
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* (MAX=2147483647, MAX/10=214748364, MAX%10=7), so the last digit is
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* rejected and scandigits aborts cleanly via fmtabort (os.exit(255)).
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*
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* row | directive | arg | want_exit
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* -----------------+--------------------+---------+----------
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* idx_2147483648 | "{2147483648}" | 42i64 | 255 (clean abort, was SIGSEGV)
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* idx_2147483649 | "{2147483649}" | 42i64 | 255 (clean abort, was SIGSEGV)
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* idx_9999999999 | "{9999999999}" | 42i64 | 255 (clear overflow, aborts pre+post)
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* width_2147483648 | "{:2147483648}" | 42i64 | 255 (width call site, last-digit abort)
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* prec_2147483647 | "{:.2147483647}" | "ok" | 7 (i32 MAX still PARSES, prints "ok")
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*
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* scandigits feeds three directive call sites — index (fmt.ww:690),
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* width (:259) and precision (:255). idx_*, width_* and prec_* exercise
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* all three; the last-digit guard must fire identically at each.
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*
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* The first two rows are the regression proper: on the pre-fix guard the
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* program is killed by signal 11 (runwait -> -1), not 255. The valid
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* boundary row proves the fix does not over-reject i32 MAX itself.
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*
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* Rule 10: every row runs on cstage `ww` and (when present) wwstage
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* `ww_ww`; both drivers compile the same fixed lib/fmt so both must agree.
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*/
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#include <stdio.h>
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#include <stdlib.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; /* killed by a signal (e.g. SIGSEGV) */
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}
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struct row {
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const char *label;
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const char *src;
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int want_exit;
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};
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static const struct row rows[] = {
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{ "idx_2147483648",
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"package main;\n"
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"import fmt;\n"
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"import io;\n"
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"export fn main() i32 = {\n"
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" let buf: [64]u8;\n"
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" let r: (str | io.error) = fmt.bsprintf(buf[0:64], \"{2147483648}\", 42i64);\n"
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" match (r) {\n"
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" case let s: str => { return 0; };\n"
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" case let e: io.error => { return 1; };\n"
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" };\n"
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"};\n",
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255 },
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{ "idx_2147483649",
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"package main;\n"
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"import fmt;\n"
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"import io;\n"
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"export fn main() i32 = {\n"
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" let buf: [64]u8;\n"
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" let r: (str | io.error) = fmt.bsprintf(buf[0:64], \"{2147483649}\", 42i64);\n"
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" match (r) {\n"
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" case let s: str => { return 0; };\n"
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" case let e: io.error => { return 1; };\n"
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" };\n"
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"};\n",
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255 },
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{ "idx_9999999999",
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"package main;\n"
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"import fmt;\n"
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"import io;\n"
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"export fn main() i32 = {\n"
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" let buf: [64]u8;\n"
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" let r: (str | io.error) = fmt.bsprintf(buf[0:64], \"{9999999999}\", 42i64);\n"
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" match (r) {\n"
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" case let s: str => { return 0; };\n"
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" case let e: io.error => { return 1; };\n"
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" };\n"
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"};\n",
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255 },
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{ "width_2147483648",
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"package main;\n"
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"import fmt;\n"
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"import io;\n"
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"export fn main() i32 = {\n"
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" let buf: [64]u8;\n"
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" let r: (str | io.error) = fmt.bsprintf(buf[0:64], \"{:2147483648}\", 42i64);\n"
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" match (r) {\n"
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" case let s: str => { return 0; };\n"
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" case let e: io.error => { return 1; };\n"
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" };\n"
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"};\n",
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255 },
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{ "prec_2147483647",
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"package main;\n"
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"import fmt;\n"
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"import io;\n"
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"export fn main() i32 = {\n"
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" let buf: [64]u8;\n"
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" let r: (str | io.error) = fmt.bsprintf(buf[0:64], \"{:.2147483647}\", \"ok\");\n"
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" match (r) {\n"
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" case let s: str => { if (s.len == 2) { return 7; }; return 8; };\n"
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" case let e: io.error => { return 1; };\n"
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" };\n"
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"};\n",
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7 },
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};
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static int
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write_source(const char *path, const char *src)
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{
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FILE *f = fopen(path, "wb");
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if (!f) return -1;
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fputs(src, f);
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fclose(f);
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return 0;
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}
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/* ww_ww writes intermediates next to the source (filed task #15); clear
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* each row's <base>.{combined.ww,s,o} + bare exe. Mirror of 780's. */
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static void
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cleanup_tmp(const char *tmpdir, const char *base)
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{
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char p[640];
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snprintf(p, sizeof p, "%s/%s.ww", tmpdir, base); unlink(p);
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snprintf(p, sizeof p, "%s/%s.s", tmpdir, base); unlink(p);
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snprintf(p, sizeof p, "%s/%s.o", tmpdir, base); unlink(p);
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snprintf(p, sizeof p, "%s/%s.combined.ww", tmpdir, base); unlink(p);
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snprintf(p, sizeof p, "%s/%s", tmpdir, base); unlink(p);
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rmdir(tmpdir);
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}
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static int
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build_via_driver(const char *driver, const char *tmpdir, const char *cwd,
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const char *src)
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{
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char cmd[2048];
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snprintf(cmd, sizeof cmd,
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"cd %s && timeout 180 %s build -I %s/lib %s 2>/dev/null",
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tmpdir, driver, cwd, src);
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return runwait(cmd);
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}
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static int
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run_row(const char *driver, const char *cwd, const struct row *r, int seq)
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{
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char tmpdir[256], src[512], base[64], outbin[768];
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snprintf(tmpdir, sizeof tmpdir, "/tmp/fso_%d_d_%d", getpid(), seq);
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snprintf(base, sizeof base, "main989so");
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snprintf(src, sizeof src, "%s/%s.ww", tmpdir, base);
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mkdir(tmpdir, 0755);
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if (write_source(src, r->src) != 0) { cleanup_tmp(tmpdir, base); return -2; }
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int rc;
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int br = build_via_driver(driver, tmpdir, cwd, src);
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if (br == 0) {
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snprintf(outbin, sizeof outbin, "%s/%s", tmpdir, base);
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rc = runwait(outbin);
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} else {
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rc = -3; /* build failure: distinct from a run signal */
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}
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cleanup_tmp(tmpdir, base);
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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 cwd[256];
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if (getcwd(cwd, sizeof cwd) == NULL) return 1;
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char absbin[512];
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if (bin[0] != '/') {
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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[640], wdrv[640];
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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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int n = (int)(sizeof rows / sizeof rows[0]);
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int total = 0, fail = 0;
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int wwpresent = (access(wdrv, X_OK) == 0);
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int seq = 0;
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for (int i = 0; i < n; i++) {
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total++;
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int got = run_row(cdrv, cwd, &rows[i], seq++);
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if (got != rows[i].want_exit) {
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fprintf(stderr,
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"fmt_scanoverflow[cs][%s]: exit=%d want=%d\n",
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rows[i].label, got, rows[i].want_exit);
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fail++;
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}
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if (wwpresent) {
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total++;
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got = run_row(wdrv, cwd, &rows[i], seq++);
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if (got != rows[i].want_exit) {
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fprintf(stderr,
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"fmt_scanoverflow[ww][%s]: exit=%d want=%d\n",
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rows[i].label, got, rows[i].want_exit);
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fail++;
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}
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}
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}
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if (!wwpresent)
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fprintf(stderr, "fmt_scanoverflow: skip wwstage (no %s)\n", wdrv);
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if (fail) {
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fprintf(stderr, "fmt_scanoverflow: %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("fmt_scanoverflow: %d/%d ok\n", total, total);
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return 0;
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}
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