No, this is about `inline asm` (i.e `__asm`), not `inline`. :)

`inline` is a C99 standard feature [1], but `__asm` (`__asm__`, `asm`)
isn't [2][3].

And my goal is not building the whole OpenBSD project with another
compiler; I just want my (and others') home brewed C compiler could be
able to process at least the C standard headers.

[1]: http://port70.net/%7Ensz/c/c99/n1256.html#6.7.4
[2]: https://gcc.gnu.org/onlinedocs/gcc/Extended-Asm.html
[3]: https://stackoverflow.com/a/49830990

On Sun, Dec 31, 2023, at 9:18 PM, Jonathan Gray wrote:
> On Sun, Dec 31, 2023 at 08:36:52PM -0800, Chenguang Wang wrote:
>> Hi,
>> 
>> It seems that /usr/include/machine/endian.h uses inline asm, which is a
>> GNU C extension, without guarding it with __GNUC__. This header is a
>> dependency of stdio.h, which means any C compiler that wants to #include
>> stdio.h is required to implement the asm extension. This has been
>> causing troubles in the cproc C11 compiler; they had to patch that
>> header file [1] in their automated testing setup for OpenBSD.
>
> __inline is defined by cdefs.h which endian.h includes
>
> For a C compiler not defining __GNUC__ it gets defined to nothing.
> Untested diff below to define it to inline for >= c99.
>
> I would not be surprised if other things are broken when __GNUC__
> is not defined.  The pcc revival started out that way but soon changed.
>
> Index: sys/sys/cdefs.h
> ===================================================================
> RCS file: /cvs/src/sys/sys/cdefs.h,v
> diff -u -p -r1.43 cdefs.h
> --- sys/sys/cdefs.h	29 Oct 2018 17:10:40 -0000	1.43
> +++ sys/sys/cdefs.h	1 Jan 2024 05:10:36 -0000
> @@ -66,8 +66,9 @@
>  #define	__const		const		/* define reserved names to standard */
>  #define	__signed	signed
>  #define	__volatile	volatile
> -#if defined(__cplusplus) || defined(__PCC__)
> -#define	__inline	inline		/* convert to C++ keyword */
> +#if defined(__cplusplus) || \
> +    (defined(__STDC_VERSION__) && __STDC_VERSION__ >= 199901)
> +#define	__inline	inline		/* convert to C++/C99 keyword */
>  #else
>  #if !defined(__GNUC__)
>  #define	__inline			/* delete GCC keyword */