Re: [PATCH] qemu/atomic.h: add #ifdef guards for stdatomic.h

[Paolo Bonzini]

On 26/03/20 18:14, Peter Maydell wrote:
>> +#ifndef atomic_fetch_add
>>  #define atomic_fetch_add(ptr, n) __atomic_fetch_add(ptr, n, 
>> __ATOMIC_SEQ_CST)
>>  #define atomic_fetch_sub(ptr, n) __atomic_fetch_sub(ptr, n, 
>> __ATOMIC_SEQ_CST)
>>  #define atomic_fetch_and(ptr, n) __atomic_fetch_and(ptr, n, 
>> __ATOMIC_SEQ_CST)
>>  #define atomic_fetch_or(ptr, n)  __atomic_fetch_or(ptr, n, __ATOMIC_SEQ_CST)
>>  #define atomic_fetch_xor(ptr, n) __atomic_fetch_xor(ptr, n, 
>> __ATOMIC_SEQ_CST)
>> +#endif
>
> This will work around FreeBSD's current implementation in particular,
> but I don't think there's anything in the C11 spec that mandates that
> atomic_fetch_add() and friends have to be macros and not simply
> functions...

That's not a problem as long as they are all functions, the macros would
simply override the function-based implementation.

Paolo