linux-kernel - Re: [PATCH v3 05/14] tools/nolibc: stdint: use int for size

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Date:   Sat, 5 Aug 2023 18:35:24 +0200
From:   Willy Tarreau <w@....eu>
To:     Thomas Weißschuh <linux@...ssschuh.net>
Cc:     Shuah Khan <shuah@...nel.org>, linux-kselftest@...r.kernel.org,
        linux-kernel@...r.kernel.org, Yuan Tan <tanyuan@...ylab.org>,
        Zhangjin Wu <falcon@...ylab.org>
Subject: Re: [PATCH v3 05/14] tools/nolibc: stdint: use int for size_t on
 32bit

On Sat, Aug 05, 2023 at 06:25:52PM +0200, Thomas Weißschuh wrote:
> On 2023-08-05 18:19:29+0200, Willy Tarreau wrote:
> > Hi Thomas,
> > 
> > On Thu, Aug 03, 2023 at 09:28:49AM +0200, Thomas Weißschuh wrote:
> > > Otherwise both gcc and clang may generate warnings about type
> > > mismatches:
> > > 
> > > sysroot/mips/include/string.h:12:14: warning: mismatch in argument 1 type of built-in function 'malloc'; expected 'unsigned int' [-Wbuiltin-declaration-mismatch]
> > >    12 | static void *malloc(size_t len);
> > >       |              ^~~~~~
> > > 
> > > Signed-off-by: Thomas Weißschuh <linux@...ssschuh.net>
> > > ---
> > >  tools/include/nolibc/stdint.h | 4 ++++
> > >  1 file changed, 4 insertions(+)
> > > 
> > > diff --git a/tools/include/nolibc/stdint.h b/tools/include/nolibc/stdint.h
> > > index 4b282435a59a..0f390c3028d8 100644
> > > --- a/tools/include/nolibc/stdint.h
> > > +++ b/tools/include/nolibc/stdint.h
> > > @@ -15,7 +15,11 @@ typedef unsigned int       uint32_t;
> > >  typedef   signed int        int32_t;
> > >  typedef unsigned long long uint64_t;
> > >  typedef   signed long long  int64_t;
> > > +#if __SIZE_WIDTH__ == 64
> > >  typedef unsigned long        size_t;
> > > +#else
> > > +typedef unsigned int         size_t;
> > > +#endif
> > 
> > This one breaks gcc < 7 for me because __SIZE_WIDTH__ is not defined
> > there. However I could trace __SIZE_TYPE__ to be defined since at least
> > gcc-3.4 so instead we can do this, which will always match the type set
> > by the compiler (either "unsigned int" or "unsigned long int") :
> > 
> >   #ifdef __SIZE_TYPE__
> >   typedef __SIZE_TYPE__ size_t;
> >   #else
> >   typedef unsigned long size_t;
> >   #endif
> 
> Sounds good. But do we need the fallback?

I don't know. It's always the same when using a compiler-defined macro
that you discover when you need it, you never know how spread it is.
At least I've also found it in clang as old as 3.8, so maybe it can be
considered safe enough.

> Further below we are also unconditionally using preprocessor-defines
> like __INT_MAX__ and __LONG_MAX__.
> 
> So I guess we can drop the proposed #ifdef.

I'll try with this, the risk is quite low anyway (famous last words).

> > Please just let me know if you want me to modify your patch accordingly.
> > I'm still continuing the tests.
> 
> Feel free to modify the patch.

Will do, thanks!

Willy