From a294f067a96bdc0fb696af785940ac4f8bb18f22 Mon Sep 17 00:00:00 2001
From: Feoramund <161657516+Feoramund@users.noreply.github.com>
Date: Mon, 15 Apr 2024 05:28:22 -0400
Subject: [PATCH] Fix `big.internal_random_prime` with `Second_MSB_On`

---
 core/math/big/prime.odin | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/core/math/big/prime.odin b/core/math/big/prime.odin
index b02b7cb4e..5e7c02f37 100644
--- a/core/math/big/prime.odin
+++ b/core/math/big/prime.odin
@@ -1247,6 +1247,20 @@ internal_random_prime :: proc(a: ^Int, size_in_bits: int, trials: int, flags :=
 			a.digit[0] |= 3
 		}
 		if .Second_MSB_On in flags {
+			/*
+				Ensure there's enough space for the bit to be set.
+			*/
+			if a.used * _DIGIT_BITS < size_in_bits - 1 {
+				new_size := (size_in_bits - 1) / _DIGIT_BITS
+
+				if new_size % _DIGIT_BITS > 0 {
+					new_size += 1
+				}
+
+				internal_grow(a, new_size) or_return
+				a.used = new_size
+			}
+
 			internal_int_bitfield_set_single(a, size_in_bits - 2) or_return
 		}