Add support for anonymous shared IO buffers. (#6580)

1 files changed, 3 insertions, 0 deletions

diff --git a/include/ruby/io/buffer.h b/include/ruby/io/buffer.h
index dd92db5bbe..88e5598066 100644
--- a/include/ruby/io/buffer.h
+++ b/include/ruby/io/buffer.h
@@ -37,6 +37,9 @@ enum rb_io_buffer_flags {
     // A non-private mapping is marked as external.
     RB_IO_BUFFER_MAPPED = 4,
 
+    // A mapped buffer that is also shared.
+    RB_IO_BUFFER_SHARED = 8,
+
     // The buffer is locked and cannot be resized.
     // More specifically, it means we can't change the base address or size.
     // A buffer is typically locked before a system call that uses the data.