linux-kernel - Re: [PATCH] tools/nolibc: ensure fast64 integer types have 64 bits

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Date:   Sun, 4 Jun 2023 14:03:19 +0200
From:   Thomas Weißschuh <thomas@...ch.de>
To:     Willy Tarreau <w@....eu>
Cc:     Shuah Khan <shuah@...nel.org>,
        "Paul E. McKenney" <paulmck@...nel.org>,
        Vincent Dagonneau <v@....io>, linux-kernel@...r.kernel.org,
        linux-kselftest@...r.kernel.org
Subject: Re: [PATCH] tools/nolibc: ensure fast64 integer types have 64 bits

On 2023-06-04 13:59:42+0200, Willy Tarreau wrote:
> On Sun, Jun 04, 2023 at 12:50:03PM +0200, Willy Tarreau wrote:
> > On Tue, May 30, 2023 at 11:18:00AM +0200, Thomas Weißschuh wrote:
> > > On 32bit platforms size_t is not enough to represent [u]int_fast64_t.
> > > 
> > > Fixes: 3e9fd4e9a1d5 ("tools/nolibc: add integer types and integer limit macros")
> > > Signed-off-by: Thomas Weißschuh <linux@...ssschuh.net>
> > > ---
> > > Cc: Vincent Dagonneau <v@....io>
> > > 
> > > Note: We could also fall back to compiler-provided data like:
> > > 
> > > __UINT_FAST{8,16,32,64}_{TYPE,MIN,MAX}__
> > 
> > I'm fine with the way you did it. I'm wondering how we managed to miss
> > this one given the tests in place!
> 
> BTW, it failed on 32-bit platforms:
> 
> 4407 tests passed, 84 skipped, 63 failed
> $ grep '^linux_arch\|FAIL' test14.out
> linux_arch=i386 qemu_arch=i386 gcc_arch=i386
> 52 limit_int_fast64_min = -2147483648                           [FAIL]
> 53 limit_int_fast64_max = 2147483647                            [FAIL]
> 54 limit_uint_fast64_max = 4294967295                           [FAIL]
> 
> The reason is that the constants also have to be adjusted. With the fix
> below everything works right:
> 
> --- a/tools/include/nolibc/stdint.h
> +++ b/tools/include/nolibc/stdint.h
> @@ -84,17 +84,17 @@ typedef uint64_t          uintmax_t;
>  #define  INT_FAST8_MIN   INT8_MIN
>  #define INT_FAST16_MIN   INTPTR_MIN
>  #define INT_FAST32_MIN   INTPTR_MIN
> -#define INT_FAST64_MIN   INTPTR_MIN
> +#define INT_FAST64_MIN   INT64_MIN
>  
>  #define  INT_FAST8_MAX   INT8_MAX
>  #define INT_FAST16_MAX   INTPTR_MAX
>  #define INT_FAST32_MAX   INTPTR_MAX
> -#define INT_FAST64_MAX   INTPTR_MAX
> +#define INT_FAST64_MAX   INT64_MAX
>  
>  #define  UINT_FAST8_MAX  UINT8_MAX
>  #define UINT_FAST16_MAX  SIZE_MAX
>  #define UINT_FAST32_MAX  SIZE_MAX
> -#define UINT_FAST64_MAX  SIZE_MAX
> +#define UINT_FAST64_MAX  UINT64_MAX
>  
>  #ifndef INT_MIN
>  #define INT_MIN          (-__INT_MAX__ - 1)
> 
> 
> 4470 tests passed, 84 skipped, 0 failed
> $ grep '^linux_arch\|fast64' test15.out 
> linux_arch=i386 qemu_arch=i386 gcc_arch=i386
> 52 limit_int_fast64_min = -9223372036854775808                   [OK]
> 53 limit_int_fast64_max = 9223372036854775807                    [OK]
> 54 limit_uint_fast64_max = -1                                    [OK]
> 
> If you're fine with it, I'll squash it into your patch.

Yes, please do so.

Fitting quote:

"I'm wondering how we managed to miss this one given the tests in place!"