From Newsgroup: comp.lang.c++
Now everything works correctly with Windows and Unix.
I wrote a framework to catch SIGSEGV thread-specific (see below).
#pragma once
#if defined(_WIN32)
#include <Windows.h>
#include "inline.hpp"
#elif defined(__unix__)
#include "signal_scope.hpp"
#else
#error
#endif
#include <atomic>
#include <bit>
template<typename T>
struct lockfree_stack
{
struct node : T
{
using T::T;
private:
template<typename T2>
friend struct lockfree_stack;
node *next;
};
void push( node *nd ) noexcept;
node *pop() noexcept;
private:
// static_assert(std::bit_floor( sizeof(node) ) == sizeof(node));
struct head { node *ptr; size_t ctr; };
static constexpr size_t Align = 2 * sizeof(size_t);
alignas(Align) head m_head = { nullptr, 0 };
#if defined(_WIN32) && defined(__clang__)
NOINLINE static node *getNext( node *nd );
#endif
};
template<typename T>
void lockfree_stack<T>::push( node *nd ) noexcept
{
using namespace std;
if( !nd ) [[unlikely]]
return;
atomic_ref<node *> ptr( m_head.ptr );
atomic_ref<size_t> ctr( m_head.ctr );
head hdRef( ptr.load( memory_order_relaxed ), ctr.load( memory_order_relaxed ) );
atomic_ref<head> aHead( m_head );
do [[unlikely]]
nd->next = hdRef.ptr;
while( !aHead.compare_exchange_strong( hdRef, head( nd, hdRef.ctr + 1 ), memory_order_release, memory_order_relaxed ) );
}
template<typename T>
auto lockfree_stack<T>::pop() noexcept -> node *
{
using namespace std;
atomic_ref<node *> ptr( m_head.ptr );
atomic_ref<size_t> ctr( m_head.ctr );
auto load = [&] { return head( ptr.load( memory_order_relaxed ), ctr.load( memory_order_relaxed ) ); };
head hdRef = load();
atomic_ref<head> aHead( m_head );
for( ; ; )
{
if( !hdRef.ptr ) [[unlikely]]
return nullptr;
node *next;
#if defined(_WIN32)
__try
{
#if !defined(__clang__)
next = hdRef.ptr->next;
#else
next = getNext( hdRef.ptr );
#endif
}
__except( EXCEPTION_EXECUTE_HANDLER )
{
hdRef = load();
continue;
}
#elif defined(__unix__)
if( !try_sig<SIGSEGV>( [&] { next = hdRef.ptr->m_next; } ) )
{
hdRef = load();
continue;
}
#endif
if( aHead.compare_exchange_strong( hdRef, head( next, hdRef.ctr + 1 ),
memory_order_acquire, memory_order_relaxed ) ) [[likely]]
return hdRef.ptr;
}
}
#if defined(_WIN32) && defined(__clang__)
template<typename T>
NOINLINE auto lockfree_stack<T>::getNext( node *nd ) -> node *
{
return nd->next;
}
#endif
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