From: Jonathan Wakely <jwakely@redhat.com>
Date: Thu, 7 Oct 2021 17:28:04 +0000 (+0100)
Subject: libstdc++: Avoid use of hardware interference non-constant [PR102377]
X-Git-Tag: basepoints/gcc-13~4079
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=0e90799071ee78f712f3b58fca7000bc0a258ade;p=thirdparty%2Fgcc.git

libstdc++: Avoid use of hardware interference non-constant [PR102377]

libstdc++-v3/ChangeLog:

	PR libstdc++/102377
	* include/bits/atomic_wait.h (__waiter_pool_base:_S_align):
	Hardcode to 64 instead of using non-constant constant.
---

diff --git a/libstdc++-v3/include/bits/atomic_wait.h b/libstdc++-v3/include/bits/atomic_wait.h
index 35c926441467..2ac07ccd05e5 100644
--- a/libstdc++-v3/include/bits/atomic_wait.h
+++ b/libstdc++-v3/include/bits/atomic_wait.h
@@ -190,11 +190,9 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
 
     struct __waiter_pool_base
     {
-#ifdef __cpp_lib_hardware_interference_size
-    static constexpr auto _S_align = hardware_destructive_interference_size;
-#else
-    static constexpr auto _S_align = 64;
-#endif
+      // Don't use std::hardware_destructive_interference_size here because we
+      // don't want the layout of library types to depend on compiler options.
+      static constexpr auto _S_align = 64;
 
       alignas(_S_align) __platform_wait_t _M_wait = 0;