From 68bd122e5d53db1c83e3b0271875b9182354bce9 Mon Sep 17 00:00:00 2001
From: Jake Bailey <5341706+jakebailey@users.noreply.github.com>
Date: Tue, 21 Apr 2026 17:38:11 -0700
Subject: [PATCH] Fix js_atod rounding when input has more than max_digits
 significant digits

---
 dtoa.c                | 6 ++++--
 tests/test_builtin.js | 6 ++++++
 2 files changed, 10 insertions(+), 2 deletions(-)

diff --git a/dtoa.c b/dtoa.c
index ac1be8d..14b6605 100644
--- a/dtoa.c
+++ b/dtoa.c
@@ -1505,8 +1505,10 @@ double js_atod(const char *str, const char **pnext, int radix, int flags,
     }
     
     /* Use the extra digits for rounding if the base is a power of
-       two. Otherwise they are just truncated. */
-    if (radix_bits != 0 && extra_digits != 0) {
+       two. Otherwise use them as a sticky bit so that round-half-to-even
+       rounds correctly when there are non-zero digits beyond the
+       precision we kept. */
+    if (extra_digits != 0) {
         tmp0->tab[0] |= 1;
     }
     
diff --git a/tests/test_builtin.js b/tests/test_builtin.js
index 14bcc06..9d9ac31 100644
--- a/tests/test_builtin.js
+++ b/tests/test_builtin.js
@@ -398,6 +398,12 @@ function test_number()
 
     assert((1.3).toString(7), "1.2046204620462046205");
     assert((1.3).toString(35), "1.ahhhhhhhhhm");
+
+    /* parsing must use digits beyond max_digits as a sticky bit so
+       that round-half-to-even rounds in the correct direction.
+       https://github.com/bellard/quickjs/issues/452 */
+    assert(+"100000000000000000000000.000000000000001",
+           1.0000000000000001e+23);
 }
 
 function test_eval2()