[libc-commits] [libc] [libc][arc4random][patch 2/4] add ABA protected MPMCStack (PR #151361)

[Michael Jones via libc-commits]

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@@ -0,0 +1,88 @@
+//===-- Transactional Ptr for ABA prevention --------------------*- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_LIBC_SRC___SUPPORT_ABA_PTR_H
+#define LLVM_LIBC_SRC___SUPPORT_ABA_PTR_H
+
+#include "hdr/types/size_t.h"
+#include "src/__support/CPP/atomic.h"
+#include "src/__support/common.h"
+#include "src/__support/threads/sleep.h"
+
+#ifdef __GCC_HAVE_SYNC_COMPARE_AND_SWAP_16
+#define LIBC_ABA_PTR_IS_ATOMIC true
+#else
+#define LIBC_ABA_PTR_IS_ATOMIC false
+#endif
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michaelrj-google wrote:

why do we need two implementations dependant on a specific gcc feature? To start it would be much simpler to have just the one implementation and add the other as an optimization later.

https://github.com/llvm/llvm-project/pull/151361