From ad62d7809e4944f3f5e9d0f896af5be146d23b51 Mon Sep 17 00:00:00 2001
From: leviongit <levi.duncan.self@gmail.com>
Date: Thu, 4 Apr 2024 20:36:44 +0200
Subject: [PATCH] fix: `Array#shuffle(!)` result distribution

---
 mrbgems/mruby-random/src/random.c | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/mrbgems/mruby-random/src/random.c b/mrbgems/mruby-random/src/random.c
index 98d4fce4d..fdba482ee 100644
--- a/mrbgems/mruby-random/src/random.c
+++ b/mrbgems/mruby-random/src/random.c
@@ -261,7 +261,7 @@ static mrb_value
 mrb_ary_shuffle_bang(mrb_state *mrb, mrb_value ary)
 {
   if (RARRAY_LEN(ary) > 1) {
-    mrb_int i, max;
+    mrb_int i;
     rand_state *random;
     mrb_sym kname = MRB_SYM(random);
     mrb_value r;
@@ -270,13 +270,12 @@ mrb_ary_shuffle_bang(mrb_state *mrb, mrb_value ary)
     mrb_get_args(mrb, ":", &kw);
     random = check_random_arg(mrb, r);
     mrb_ary_modify(mrb, mrb_ary_ptr(ary));
-    max = RARRAY_LEN(ary);
     for (i = RARRAY_LEN(ary) - 1; i > 0; i--)  {
       mrb_int j;
       mrb_value *ptr = RARRAY_PTR(ary);
       mrb_value tmp;
 
-      j = rand_i(random, max);
+      j = rand_i(random, i + 1);
 
       tmp = ptr[i];
       ptr[i] = ptr[j];