[PATCH 02/59] stdlib: longlong.h: Do no use asm input cast for clang
H.J. Lu
hjl.tools@gmail.com
Fri Oct 17 22:36:46 GMT 2025
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.
> On gcc the cast are still useful [1] as type-checking.
>
> [1] https://gcc.gnu.org/pipermail/gcc-patches/2021-October/581722.html
> ---
> stdlib/longlong.h | 48 +++++++++++++++++++++++++++--------------------
> 1 file changed, 28 insertions(+), 20 deletions(-)
>
> diff --git a/stdlib/longlong.h b/stdlib/longlong.h
> index 4549f0a55f..2ec82d0315 100644
> --- a/stdlib/longlong.h
> +++ b/stdlib/longlong.h
> @@ -57,6 +57,14 @@
> #define attribute_hidden
> #endif
>
> +/* clang does not support output constraint as lvalue, while gcc uses it as a
> + simple type check. */
> +#ifdef __clang__
> +# define __asm_output_check_type(__type, __arg) (__arg)
> +#else
> +# define __asm_output_check_type(__type, __arg) ((__type)(__arg))
> +#endif
> +
> extern const UQItype __clz_tab[256] attribute_hidden;
>
> /* Define auxiliary asm macros.
> @@ -230,16 +238,16 @@ extern UDItype __udiv_qrnnd (UDItype *, UDItype, UDItype, UDItype);
> && W_TYPE_SIZE == 32
> #define add_ssaaaa(sh, sl, ah, al, bh, bl) \
> __asm__ ("adds %1, %4, %5\n\tadc %0, %2, %3" \
> - : "=r" ((USItype) (sh)), \
> - "=&r" ((USItype) (sl)) \
> + : "=r" __asm_output_check_type (USItype, sh), \
> + "=&r" __asm_output_check_type (USItype, sl) \
> : "%r" ((USItype) (ah)), \
> "rI" ((USItype) (bh)), \
> "%r" ((USItype) (al)), \
> "rI" ((USItype) (bl)) __CLOBBER_CC)
> #define sub_ddmmss(sh, sl, ah, al, bh, bl) \
> __asm__ ("subs %1, %4, %5\n\tsbc %0, %2, %3" \
> - : "=r" ((USItype) (sh)), \
> - "=&r" ((USItype) (sl)) \
> + : "=r" __asm_output_check_type (USItype, sh), \
> + "=&r" __asm_output_check_type (USItype, sl) \
> : "r" ((USItype) (ah)), \
> "rI" ((USItype) (bh)), \
> "r" ((USItype) (al)), \
> @@ -456,30 +464,30 @@ extern UDItype __umulsidi3 (USItype, USItype);
> #if (defined (__i386__) || defined (__i486__)) && W_TYPE_SIZE == 32
> #define add_ssaaaa(sh, sl, ah, al, bh, bl) \
> __asm__ ("add{l} {%5,%1|%1,%5}\n\tadc{l} {%3,%0|%0,%3}" \
> - : "=r" ((USItype) (sh)), \
> - "=&r" ((USItype) (sl)) \
> + : "=r" __asm_output_check_type (USItype, sh), \
> + "=&r" __asm_output_check_type(USItype, sl) \
> : "%0" ((USItype) (ah)), \
> "g" ((USItype) (bh)), \
> "%1" ((USItype) (al)), \
> "g" ((USItype) (bl)))
> #define sub_ddmmss(sh, sl, ah, al, bh, bl) \
> __asm__ ("sub{l} {%5,%1|%1,%5}\n\tsbb{l} {%3,%0|%0,%3}" \
> - : "=r" ((USItype) (sh)), \
> - "=&r" ((USItype) (sl)) \
> + : "=r" __asm_output_check_type (USItype, sh), \
> + "=&r" __asm_output_check_type (USItype, sl) \
> : "0" ((USItype) (ah)), \
> "g" ((USItype) (bh)), \
> "1" ((USItype) (al)), \
> "g" ((USItype) (bl)))
> #define umul_ppmm(w1, w0, u, v) \
> __asm__ ("mul{l} %3" \
> - : "=a" ((USItype) (w0)), \
> - "=d" ((USItype) (w1)) \
> + : "=a" __asm_output_check_type (USItype, w0), \
> + "=d" __asm_output_check_type (USItype, w1) \
> : "%0" ((USItype) (u)), \
> "rm" ((USItype) (v)))
> #define udiv_qrnnd(q, r, n1, n0, dv) \
> __asm__ ("div{l} %4" \
> - : "=a" ((USItype) (q)), \
> - "=d" ((USItype) (r)) \
> + : "=a" __asm_output_check_type (USItype, q), \
> + "=d" __asm_output_check_type (USItype, r) \
> : "0" ((USItype) (n0)), \
> "1" ((USItype) (n1)), \
> "rm" ((USItype) (dv)))
> @@ -492,30 +500,30 @@ extern UDItype __umulsidi3 (USItype, USItype);
> #if defined (__x86_64__) && W_TYPE_SIZE == 64
> #define add_ssaaaa(sh, sl, ah, al, bh, bl) \
> __asm__ ("add{q} {%5,%1|%1,%5}\n\tadc{q} {%3,%0|%0,%3}" \
> - : "=r" ((UDItype) (sh)), \
> - "=&r" ((UDItype) (sl)) \
> + : "=r" __asm_output_check_type (UDItype, sh), \
> + "=&r" __asm_output_check_type (UDItype, sl) \
> : "%0" ((UDItype) (ah)), \
> "rme" ((UDItype) (bh)), \
> "%1" ((UDItype) (al)), \
> "rme" ((UDItype) (bl)))
> #define sub_ddmmss(sh, sl, ah, al, bh, bl) \
> __asm__ ("sub{q} {%5,%1|%1,%5}\n\tsbb{q} {%3,%0|%0,%3}" \
> - : "=r" ((UDItype) (sh)), \
> - "=&r" ((UDItype) (sl)) \
> + : "=r" __asm_output_check_type (UDItype, sh), \
> + "=&r" __asm_output_check_type (UDItype, sl) \
> : "0" ((UDItype) (ah)), \
> "rme" ((UDItype) (bh)), \
> "1" ((UDItype) (al)), \
> "rme" ((UDItype) (bl)))
> #define umul_ppmm(w1, w0, u, v) \
> __asm__ ("mul{q} %3" \
> - : "=a" ((UDItype) (w0)), \
> - "=d" ((UDItype) (w1)) \
> + : "=a" __asm_output_check_type (UDItype, w0), \
> + "=d" __asm_output_check_type (UDItype, w1) \
> : "%0" ((UDItype) (u)), \
> "rm" ((UDItype) (v)))
> #define udiv_qrnnd(q, r, n1, n0, dv) \
> __asm__ ("div{q} %4" \
> - : "=a" ((UDItype) (q)), \
> - "=d" ((UDItype) (r)) \
> + : "=a" __asm_output_check_type (UDItype, q), \
> + "=d" __asm_output_check_type (UDItype, r) \
> : "0" ((UDItype) (n0)), \
> "1" ((UDItype) (n1)), \
> "rm" ((UDItype) (dv)))
> --
> 2.43.0
>
--
H.J.
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