[PATCH 02/59] stdlib: longlong.h: Do no use asm input cast for clang

[H.J. Lu]

On Mon, Oct 20, 2025 at 8:46 PM Adhemerval Zanella Netto
<adhemerval.zanella@linaro.org> wrote:
>
>
>
> On 17/10/25 19:36, H.J. Lu wrote:
> > On Sat, Oct 18, 2025 at 3:23 AM Adhemerval Zanella
> > <adhemerval.zanella@linaro.org> wrote:
> >>
> >> clang 18 and 19 rejects the input casts with:
> >>
> >>   error: invalid use of a cast in a inline asm context requiring an lvalue: remove the cast or build with -fheinous-gnu-extensions
> >>
> >> While clang 20 and 21 throws a different error:
> >>
> >>   strtod_l.c:1502:20: error: invalid use of a cast in an inline asm context requiring an lvalue
> >>       [-Winvalid-gnu-asm-cast]
> >>
> >> And even with -fheinous-gnu-extensions clang issues an warning
> >> that can only be supressed with clang 20/21 (and the option might
> >> also might be removed in the future).
> >
> > This file is copied from GCC.   It should be modified in GCC first.
> >
> Fangrui tries to make a similar change back em 2021 [1], and I tried
> to make a similar change again in 2023 [2]. The impression I had was
> that gcc developers do not want to make any changes on the header
> to handle clang requirements.  I really do not want to get stalled
> again in gcc maillist for this simple fix.
>
> Since Joseph said is not a good idea to diverge between implementations,
> another possibility is to get rid of longlong.h by using stdbit.h and
> mode the required definitions on sysdeps using a more modern definition
> (function instead the spaghetti macro).  The problem with this approach
> is this also touches shared code with gcc, and thus we will have similar
> problems.
>
> I thought about a hack solution which is to pre-process this header
> with some script to generate another one at build time; but I do not
> want to go on this path.

We can rename GCC  longlong.h to longlong.h.gcc and update configure.ac
to generate longlong.h from longlong.h.gcc at build time.    When building
with GCC, longlong.h.gcc should be copied to longlong.h without any changes.

> [1] https://gcc.gnu.org/pipermail/gcc-patches/2021-October/581257.html
> [2] https://gcc.gnu.org/pipermail/gcc-patches/2023-January/609671.html



-- 
H.J.