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4480. <stdatomic.h> should provide ATOMIC_CHAR8_T_LOCK_FREE

Section: 32.5.12 [stdatomic.h.syn] Status: New Submitter: Jiang An Opened: 2025-11-21 Last modified: 2025-11-23

Priority: Not Prioritized

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Discussion:

Currently, <stdatomic.h> is specified to provide atomic_char8_t but not its corresponding ATOMIC_CHAR8_T_LOCK_FREE macro, which is self-inconsistent. Also, given WG14 N2653 added ATOMIC_CHAR8_T_LOCK_FREE to C's <stdatomic.h> in C23, perhaps C++ should do the same thing in the spirit of P3348R4.

Proposed resolution:

This wording is relative to N5014.

1. Modify 32.5.12 [stdatomic.h.syn], header <stdatomic.h> synopsis, as indicated:

   template<class T>
     using std-atomic = std::atomic<T>; // exposition only
   
   #define _Atomic(T) std-atomic<T>
   
   #define ATOMIC_BOOL_LOCK_FREE see below
   #define ATOMIC_CHAR_LOCK_FREE see below
   #define ATOMIC_CHAR8_T_LOCK_FREE see below
   #define ATOMIC_CHAR16_T_LOCK_FREE see below
   #define ATOMIC_CHAR32_T_LOCK_FREE see below
   #define ATOMIC_WCHAR_T_LOCK_FREE see below
   #define ATOMIC_SHORT_LOCK_FREE see below
   #define ATOMIC_INT_LOCK_FREE see below
   #define ATOMIC_LONG_LOCK_FREE see below
   #define ATOMIC_LLONG_LOCK_FREE see below
   #define ATOMIC_POINTER_LOCK_FREE see below
   
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