From 9ad34da47ff7d71446e667897559047ed5635b60 Mon Sep 17 00:00:00 2001
From: Nobuyoshi Nakada <nobu@ruby-lang.org>
Date: Mon, 13 Dec 2021 13:05:40 +0900
Subject: [PATCH] [DOC] Mention RBOOL in extension.rdoc [Feature #13125]

---
 doc/extension.ja.rdoc | 15 +++++++++++++++
 doc/extension.rdoc    | 15 +++++++++++++++
 2 files changed, 30 insertions(+)

diff --git a/doc/extension.ja.rdoc b/doc/extension.ja.rdoc
index 3b68ec6cbc..feae7b97da 100644
--- a/doc/extension.ja.rdoc
+++ b/doc/extension.ja.rdoc
@@ -190,6 +190,21 @@ INT2NUM() :: 任意の整数からVALUEへ
 INT2NUM()は整数がFIXNUMの範囲に収まらない場合，Bignumに変換
 してくれます(が，少し遅い)．
 
+Cの真偽値をRubyの +true+ または +false+ に変換する
+
+RBOOL() ::
+
+<code>RBOOL(v)</code> は _v_ が非0のとき +Qtrue+ ，それ以外
+の _v_ が0のとき +Qfalse+ を返します．
+
+注意: RBOOLは定義されているのはRuby 3.1以降なので，それより
+古いバージョンをサポートするプログラム中で使いたいときは，以
+下のような定義を追加しておく必要があるでしょう．
+
+    #ifndef RBOOL
+    #define RBOOL(v) ((v) ? Qtrue : Qfalse)
+    #endif
+
 === Rubyのデータを操作する
 
 先程も述べた通り，Rubyの構造体をアクセスする時に内容の更新を
diff --git a/doc/extension.rdoc b/doc/extension.rdoc
index 15417179e1..12cff6b497 100644
--- a/doc/extension.rdoc
+++ b/doc/extension.rdoc
@@ -169,6 +169,21 @@ INT2NUM() :: for arbitrary sized integers.
 INT2NUM() converts an integer into a Bignum if it is out of the FIXNUM
 range, but is a bit slower.
 
+To convert C boolean to Ruby +true+ or +false+ :
+
+RBOOL() ::
+
+<code>RBOOL(v)</code> returns +Qtrue+ if _v_ is not 0, or +Qfalse+
+otherwisze _v_ is 0.
+
+Notice: RBOOL is defined since Ruby 3.1, if you want to use it in a
+program which supports older versions, the fallback definition will be
+needed, like as the following.
+
+    #ifndef RBOOL
+    #define RBOOL(v) ((v) ? Qtrue : Qfalse)
+    #endif
+
 === Manipulating Ruby Data
 
 As I already mentioned, it is not recommended to modify an object's