Re: [GIT PULL v2] Kbuild updates for v5.15-rc1

From: Segher Boessenkool
Date: Tue Sep 07 2021 - 10:57:02 EST

On Mon, Sep 06, 2021 at 11:52:18PM +0200, Jakub Jelinek wrote:
> On Mon, Sep 06, 2021 at 02:08:58PM -0700, Linus Torvalds wrote:
> There is a stddef.h include too and that's it
> (I must say I don't see the reason for that include though).

Yeah me neither. Maybe the header used NULL before?

> Other compiler provided headers (not talking about C++ now) also have no
> or very limited includes, including stddef.h, stdarg.h, stdatomic.h, etc.
> The only exceptions are tgmath.h which isn't usable without libc
> math.h/complex.h,

<tgmath.h> is only for hosted environments. That requires a C library
for GCC (we do not implement this stuff ourselves). The compiler and
the C library have to work together to get this done, and the relation
between GCC and Glibc has been a bit too tight for this, it is true.

But a kernel build is not in a hosted environment.

> in some cases stdint.h and limits.h which are in some
> configurations provided both by the C library and the compiler and include
> each other in that case (but e.g. stdint.h has an alternate version that
> only uses compiler provided builtin macros) and openacc.h.

On what targets is <stdint.h> still problematic? And <limits.h>?