From 4ae9ab70cd3214395756435d13d8d000368ca2cb Mon Sep 17 00:00:00 2001
From: Lasse Collin <lasse.collin@tukaani.org>
Date: Sun, 26 Jan 2020 13:37:08 +0200
Subject: [PATCH] xz: Update a comment in file_io.h.

---
 src/xz/file_io.h | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/src/xz/file_io.h b/src/xz/file_io.h
index ff6fb80a..4b4418d6 100644
--- a/src/xz/file_io.h
+++ b/src/xz/file_io.h
@@ -20,7 +20,10 @@
 
 
 /// is_sparse() accesses the buffer as uint64_t for maximum speed.
-/// Use an union to make sure that the buffer is properly aligned.
+/// The u32 and u64 members must only be access through this union
+/// to avoid strict aliasing violations. Taking a pointer of u8
+/// should be fine as long as uint8_t maps to unsigned char which
+/// can alias anything.
 typedef union {
 	uint8_t u8[IO_BUFFER_SIZE];
 	uint32_t u32[IO_BUFFER_SIZE / sizeof(uint32_t)];