merge revision(s) 09295ea796900fb7b05d29e93364090e21598566: [Backport #19543]

	IO::Buffer#resize: Free internal buffer if new size is zero (#7569)

	`#resize(0)` on an IO::Buffer with internal buffer allocated will
	result in calling `realloc(data->base, 0)`. The behavior of `realloc`
	with size = 0 is implementation-defined (glibc frees the object
	and returns NULL, while BSDs return an inaccessible object). And
	thus such usage is deprecated in standard C (upcoming C23 will make it
	UB).

	To avoid this problem, just `free`s the memory when the new size is zero.
	---
	 io_buffer.c                 |  5 +++++
	 test/ruby/test_io_buffer.rb | 18 ++++++++++++++++++
	 2 files changed, 23 insertions(+)

3 files changed, 24 insertions, 1 deletions

diff --git a/io_buffer.c b/io_buffer.c
index 0ca6ec5632..5951f54fc4 100644
--- a/io_buffer.c
+++ b/io_buffer.c
@@ -1308,6 +1308,11 @@ rb_io_buffer_resize(VALUE self, size_t size)
 #endif
 
     if (data->flags & RB_IO_BUFFER_INTERNAL) {
+        if (size == 0) {
+            io_buffer_free(data);
+            return;
+        }
+
         void *base = realloc(data->base, size);
 
         if (!base) {
diff --git a/test/ruby/test_io_buffer.rb b/test/ruby/test_io_buffer.rb
index e3f7021b26..fdfea00dfe 100644
--- a/test/ruby/test_io_buffer.rb
+++ b/test/ruby/test_io_buffer.rb
@@ -142,6 +142,24 @@ class TestIOBuffer < Test::Unit::TestCase
     assert_equal message, buffer.get_string(0, message.bytesize)
   end
 
+  def test_resize_zero_internal
+    buffer = IO::Buffer.new(1)
+
+    buffer.resize(0)
+    assert_equal 0, buffer.size
+
+    buffer.resize(1)
+    assert_equal 1, buffer.size
+  end
+
+  def test_resize_zero_external
+    buffer = IO::Buffer.for('1')
+
+    assert_raise IO::Buffer::AccessError do
+      buffer.resize(0)
+    end
+  end
+
   def test_compare_same_size
     buffer1 = IO::Buffer.new(1)
     assert_equal buffer1, buffer1
diff --git a/version.h b/version.h
index b180a80352..3e6dccb31b 100644
--- a/version.h
+++ b/version.h
@@ -11,7 +11,7 @@
 # define RUBY_VERSION_MINOR RUBY_API_VERSION_MINOR
 #define RUBY_VERSION_TEENY 4
 #define RUBY_RELEASE_DATE RUBY_RELEASE_YEAR_STR"-"RUBY_RELEASE_MONTH_STR"-"RUBY_RELEASE_DAY_STR
-#define RUBY_PATCHLEVEL 233
+#define RUBY_PATCHLEVEL 234
 
 #define RUBY_RELEASE_YEAR 2023
 #define RUBY_RELEASE_MONTH 7