From b82f1c2ec0bee06161a45c057aaf0d72bab2b394 Mon Sep 17 00:00:00 2001
From: Yasuhiro Matsumoto <mattn.jp@gmail.com>
Date: Thu, 16 Apr 2026 14:41:01 +0900
Subject: [PATCH] readfloat.c: keep one extra fraction digit (17 -> 18)

18 decimal digits still fit in uint64_t (max ~1.8e19), so we can hold
one more digit of precision without overflow risk.
---
 src/readfloat.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/readfloat.c b/src/readfloat.c
index 8de734a32..cb23d7f71 100644
--- a/src/readfloat.c
+++ b/src/readfloat.c
@@ -144,7 +144,7 @@ mrb_read_float(const char *str, char **endp, double *fp)
   // Parse fractional part
   if (*p == '.') {
     p++;
-    while (ISDIGIT(*p) && frac_digits < 17) { // Limit precision to avoid overflow
+    while (ISDIGIT(*p) && frac_digits < 18) { // Limit precision to avoid overflow
       frac_part = frac_part * 10 + (*p - '0');
       frac_digits++;
       digits++;