From cd95fc28fb6d8afced0d70ce52c294d0761a9daa Mon Sep 17 00:00:00 2001 From: Peter Maydell Date: Thu, 10 May 2018 18:10:57 +0100 Subject: [PATCH] atomic.h: Work around gcc spurious "unused value" warning MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit Some versions of gcc produce a spurious warning if the result of __atomic_compare_echange_n() is not used and the type involved is a signed 8 bit value: error: value computed is not used [-Werror=unused-value] This has been seen on at least gcc (Ubuntu 5.4.0-6ubuntu1~16.04.9) 5.4.0 20160609 Work around this by using an explicit cast to void to indicate that we don't care about the return value. We don't currently use our atomic_cmpxchg() macro on any signed 8 bit types, but the upcoming support for the Arm v8.1-Atomics will require it. Signed-off-by: Peter Maydell Reviewed-by: Richard Henderson Reviewed-by: Philippe Mathieu-Daudé --- include/qemu/atomic.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/include/qemu/atomic.h b/include/qemu/atomic.h index d73c9e14d7..9ed39effd3 100644 --- a/include/qemu/atomic.h +++ b/include/qemu/atomic.h @@ -187,7 +187,7 @@ /* Returns the eventual value, failed or not */ #define atomic_cmpxchg__nocheck(ptr, old, new) ({ \ typeof_strip_qual(*ptr) _old = (old); \ - __atomic_compare_exchange_n(ptr, &_old, new, false, \ + (void)__atomic_compare_exchange_n(ptr, &_old, new, false, \ __ATOMIC_SEQ_CST, __ATOMIC_SEQ_CST); \ _old; \ }) -- 2.30.2