[libcxx-commits] [libcxx] r368916 - Fix thread comparison by making sure we never pass our special 'not a thread' value to the underlying implementation. Fixes PR#42918.

[Hans Wennborg via libcxx-commits]

Merged together with r368867 to release_90 in r369369.

On Wed, Aug 14, 2019 at 10:53 PM Marshall Clow via libcxx-commits
<libcxx-commits at lists.llvm.org> wrote:
>
> Author: marshall
> Date: Wed Aug 14 13:54:56 2019
> New Revision: 368916
>
> URL: http://llvm.org/viewvc/llvm-project?rev=368916&view=rev
> Log:
> Fix thread comparison by making sure we never pass our special 'not a thread' value to the underlying implementation. Fixes PR#42918.
>
> Modified:
>     libcxx/trunk/include/__threading_support
>     libcxx/trunk/src/mutex.cpp
>
> Modified: libcxx/trunk/include/__threading_support
> URL: http://llvm.org/viewvc/llvm-project/libcxx/trunk/include/__threading_support?rev=368916&r1=368915&r2=368916&view=diff
> ==============================================================================
> --- libcxx/trunk/include/__threading_support (original)
> +++ libcxx/trunk/include/__threading_support Wed Aug 14 13:54:56 2019
> @@ -420,13 +420,21 @@ public:
>
>      friend _LIBCPP_INLINE_VISIBILITY
>          bool operator==(__thread_id __x, __thread_id __y) _NOEXCEPT
> -        {return __libcpp_thread_id_equal(__x.__id_, __y.__id_);}
> +        { // don't pass id==0 to underlying routines
> +        if (__x.__id_ == 0) return __y.__id_ == 0;
> +        if (__y.__id_ == 0) return false;
> +        return __libcpp_thread_id_equal(__x.__id_, __y.__id_);
> +        }
>      friend _LIBCPP_INLINE_VISIBILITY
>          bool operator!=(__thread_id __x, __thread_id __y) _NOEXCEPT
>          {return !(__x == __y);}
>      friend _LIBCPP_INLINE_VISIBILITY
>          bool operator< (__thread_id __x, __thread_id __y) _NOEXCEPT
> -        {return  __libcpp_thread_id_less(__x.__id_, __y.__id_);}
> +        { // id==0 is always less than any other thread_id
> +        if (__x.__id_ == 0) return __y.__id_ != 0;
> +        if (__y.__id_ == 0) return false;
> +        return  __libcpp_thread_id_less(__x.__id_, __y.__id_);
> +        }
>      friend _LIBCPP_INLINE_VISIBILITY
>          bool operator<=(__thread_id __x, __thread_id __y) _NOEXCEPT
>          {return !(__y < __x);}
> @@ -438,7 +446,7 @@ public:
>          {return !(__x < __y);}
>
>      _LIBCPP_INLINE_VISIBILITY
> -    void reset() { __id_ = 0; }
> +    void __reset() { __id_ = 0; }
>
>      template<class _CharT, class _Traits>
>      friend
>
> Modified: libcxx/trunk/src/mutex.cpp
> URL: http://llvm.org/viewvc/llvm-project/libcxx/trunk/src/mutex.cpp?rev=368916&r1=368915&r2=368916&view=diff
> ==============================================================================
> --- libcxx/trunk/src/mutex.cpp (original)
> +++ libcxx/trunk/src/mutex.cpp Wed Aug 14 13:54:56 2019
> @@ -181,7 +181,7 @@ recursive_timed_mutex::unlock() _NOEXCEP
>      unique_lock<mutex> lk(__m_);
>      if (--__count_ == 0)
>      {
> -        __id_.reset();
> +        __id_.__reset();
>          lk.unlock();
>          __cv_.notify_one();
>      }
>
>
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