Re: [PATCH v2.5 3/3] xen/types: Rework stdint vs __{u,s}$N types

[Jan Beulich <jbeulich@xxxxxxxx>]

On 28.06.2023 16:54, Andrew Cooper wrote:
> Xen uses the stdint types.  Rearrange the types headers to define the
> compatibility __{u,s}$N types in terms of the stdint types, not the other way
> around.
> 
> All supported compilers on architectures other than x86 support the stdint
> __*_TYPE__ macros.  Move these into a new xen/stdint.h to avoid them being
> duplicated in each architecture.  For the very old x86 compilers, synthesize
> suitable types using GCC internals.
> 
> This cleanup has the side effect of removing all use of the undocumented
> __signed__ GCC keyword.  This is a vestigial remnant of `gcc -traditional`
> mode for dialetcs of C prior to the introduction of the signed keyword.
> 
> No functional change.
> 
> Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>

Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>
with one further remark:

> --- /dev/null
> +++ b/xen/include/xen/stdint.h
> @@ -0,0 +1,33 @@
> +/* SPDX-License-Identifier: GPL-2.0-only */
> +#ifndef __XEN_STDINT_H__
> +#define __XEN_STDINT_H__
> +
> +#ifndef __INT8_TYPE__ /* GCC <= 4.4 */
> +
> +/*
> + * Define the types using GCC internal notation.  Clang understands this too.
> + * https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html
> + */
> +typedef   signed __attribute__((__mode__(QI)))     int8_t;
> +typedef unsigned __attribute__((__mode__(QI)))    uint8_t;
> +typedef   signed __attribute__((__mode__(HI)))    int16_t;
> +typedef unsigned __attribute__((__mode__(HI)))   uint16_t;
> +typedef   signed __attribute__((__mode__(SI)))    int32_t;
> +typedef unsigned __attribute__((__mode__(SI)))   uint32_t;
> +typedef   signed __attribute__((__mode__(DI)))    int64_t;
> +typedef unsigned __attribute__((__mode__(DI)))   uint64_t;

Much like you avoid "mode" potentially being the name of a visible macro,
the mode identifiers themselves could in principle be, too. Being upper
case names, perhaps there the risk is even slightly higher. Hence I'd
prefer if you/we could use __QI__ and alike.

Jan