merge revision(s) c5cf4d4e129f64cb69aaf0a829aed068ef1943c4: [Backport#19542] (#9829)

merge revision(s) c5cf4d4e129f64cb69aaf0a829aed068ef1943c4: [Backport #19542]

	Improve behavioural consistency of unallocated (zero length)
	 `IO::Buffer`. (#9532)

	This makes the behaviour of IO::Buffer.new(0) and IO::Buffer.new.slice(0, 0) consistent.

	Fixes https://bugs.ruby-lang.org/issues/19542 and https://bugs.ruby-lang.org/issues/18805.
	---
	 io_buffer.c                 | 14 ++++++--------
	 test/ruby/test_io_buffer.rb | 35 +++++++++++++++++++++++++++++++++++
	 2 files changed, 41 insertions(+), 8 deletions(-)

3 files changed, 42 insertions, 9 deletions

diff --git a/io_buffer.c b/io_buffer.c
index 7e580c8633..7715aa0d37 100644
--- a/io_buffer.c
+++ b/io_buffer.c
@@ -854,11 +854,10 @@ io_buffer_get_bytes_for_writing(struct rb_io_buffer *buffer, void **base, size_t
     if (buffer->base) {
         *base = buffer->base;
         *size = buffer->size;
-
-        return;
+    } else {
+        *base = NULL;
+        *size = 0;
     }
-
-    rb_raise(rb_eIOBufferAllocationError, "The buffer is not allocated!");
 }
 
 void
@@ -880,11 +879,10 @@ io_buffer_get_bytes_for_reading(struct rb_io_buffer *buffer, const void **base,
     if (buffer->base) {
         *base = buffer->base;
         *size = buffer->size;
-
-        return;
+    } else {
+        *base = NULL;
+        *size = 0;
     }
-
-    rb_raise(rb_eIOBufferAllocationError, "The buffer is not allocated!");
 }
 
 void
diff --git a/test/ruby/test_io_buffer.rb b/test/ruby/test_io_buffer.rb
index 321b6534ee..7a58ec0c5a 100644
--- a/test/ruby/test_io_buffer.rb
+++ b/test/ruby/test_io_buffer.rb
@@ -199,6 +199,14 @@ class TestIOBuffer < Test::Unit::TestCase
     assert_positive buffer2 <=> buffer1
   end
 
+  def test_compare_zero_length
+    buffer1 = IO::Buffer.new(0)
+    buffer2 = IO::Buffer.new(1)
+
+    assert_negative buffer1 <=> buffer2
+    assert_positive buffer2 <=> buffer1
+  end
+
   def test_slice
     buffer = IO::Buffer.new(128)
     slice = buffer.slice(8, 32)
@@ -270,6 +278,14 @@ class TestIOBuffer < Test::Unit::TestCase
     end
   end
 
+  def test_zero_length_get_string
+    buffer = IO::Buffer.new.slice(0, 0)
+    assert_equal "", buffer.get_string
+
+    buffer = IO::Buffer.new(0)
+    assert_equal "", buffer.get_string
+  end
+
   # We check that values are correctly round tripped.
   RANGES = {
     :U8 => [0, 2**8-1],
@@ -316,6 +332,13 @@ class TestIOBuffer < Test::Unit::TestCase
     end
   end
 
+  def test_zero_length_get_set_values
+    buffer = IO::Buffer.new(0)
+
+    assert_equal [], buffer.get_values([], 0)
+    assert_equal 0, buffer.set_values([], 0, [])
+  end
+
   def test_values
     buffer = IO::Buffer.new(128)
 
@@ -340,6 +363,12 @@ class TestIOBuffer < Test::Unit::TestCase
     end
   end
 
+  def test_zero_length_each
+    buffer = IO::Buffer.new(0)
+
+    assert_equal [], buffer.each(:U8).to_a
+  end
+
   def test_each_byte
     string = "The quick brown fox jumped over the lazy dog."
     buffer = IO::Buffer.for(string)
@@ -347,6 +376,12 @@ class TestIOBuffer < Test::Unit::TestCase
     assert_equal string.bytes, buffer.each_byte.to_a
   end
 
+  def test_zero_length_each_byte
+    buffer = IO::Buffer.new(0)
+
+    assert_equal [], buffer.each_byte.to_a
+  end
+
   def test_clear
     buffer = IO::Buffer.new(16)
     buffer.set_string("Hello World!")
diff --git a/version.h b/version.h
index 9b9fde34c4..d5097e2003 100644
--- a/version.h
+++ b/version.h
@@ -11,7 +11,7 @@
 # define RUBY_VERSION_MINOR RUBY_API_VERSION_MINOR
 #define RUBY_VERSION_TEENY 0
 #define RUBY_RELEASE_DATE RUBY_RELEASE_YEAR_STR"-"RUBY_RELEASE_MONTH_STR"-"RUBY_RELEASE_DAY_STR
-#define RUBY_PATCHLEVEL 9
+#define RUBY_PATCHLEVEL 10
 
 #include "ruby/version.h"
 #include "ruby/internal/abi.h"