wcc: reject final-band integer overflow; restore rewind columns

cmd/wcc/lex.c

@@ -181,6 +181,9 @@ static u64
 parseint(const char *s, u64 n, int base, int *ok)
 {
 	u64 v = 0;
+	u64 b = (u64)base;
+	u64 cutoff = (u64)~0ULL / b;
+	u64 cutlim = (u64)~0ULL % b;
 	int got = 0;
 	for (u64 i = 0; i < n; i++) {
 		int c = (unsigned char)s[i];
@@ -192,9 +195,11 @@ parseint(const char *s, u64 n, int base, int *ok)
 		else if (c >= 'A' && c <= 'F') d = c - 'A' + 10;
 		else { *ok = 0; return 0; }
 		if (d >= base) { *ok = 0; return 0; }
-		/* overflow? cheap check */
-		if (v > (u64)~0ULL / (u64)base) { *ok = 0; return 0; }
-		v = v * (u64)base + (u64)d;
+		if (v > cutoff || (v == cutoff && (u64)d > cutlim)) {
+			*ok = 0;
+			return 0;
+		}
+		v = v * b + (u64)d;
 		got = 1;
 	}
 	*ok = got;
@@ -369,6 +374,7 @@ lexnum(Lex *l, Pos start)
 	/* A typed suffix must be glued (no whitespace) to the digits. */
 	if (isidstart(lpeek(l, 0))) {
 		u64 sb = l->pos;
+		i32 sc = l->col;
 		while (isidcont(lpeek(l, 0))) lget(l);
 		u64 sl = l->pos - sb;
 		const char *names[] = {
@@ -387,9 +393,8 @@ lexnum(Lex *l, Pos start)
 		if (match) {
 			t.tsuffix = astrndup(l->a, l->src + sb, sl);
 		} else {
-			/* not a known suffix — rewind so the run becomes a
-			 * separate token. */
 			l->pos = sb;
+			l->col = sc;
 		}
 	}
 	return t;