罗勇刚,
there might be a misunderstanding here, this page is not meant for
musl alone and the example code is just that, example code. How C
library implementations then do it is clearly a question of their
particular coding style.

on Wed, 23 Nov 2022 12:31:27 +0800 you (罗勇刚(Yonggang Luo)
<luoyonggang@gmail.com>) wrote:

> I have concern about the macros guard with __cplusplus and
> __STDC_VERSION__
> 
> #if (__cplusplus >= 201103L) || (__STDC_VERSION__ >= 202311L)
> #define NULL nullptr
> #elif defined(__cplusplus)
> #define NULL 0L              /* Any of 0, 0L, 0LL as wide as a void*
> */ #else
> #define NULL ((void*)0)
> #endif
> 
> 
> I think all of these should be guarded with
> #if (defined(__cplusplus) && (__cplusplus >= 201103L)) ||
> (defined(__STDC_VERSION__) && (__STDC_VERSION__ >= 202311L))
> 
> this is safer to avoid -Wundef complain it

IIRC musl's strategy has so far been to use the implicit 0 rule for
identifiers in preprocessor conditionals. But I may be mistaken.

Also, `__STDC_VERSION__` has been introduced in C95, I think, do we
even support compilers that don't have this?

Thanks
Jₑₙₛ

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