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Date:   Tue, 21 Jun 2022 15:01:24 +0200
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Subject: Re: [PATCH v3] uapi: Make __{u,s}64 match {u,}int64_t in userspace
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To:     Cyril Hrubis <chrubis@suse.cz>, linux-kernel@vger.kernel.org
Cc:     linux-arch@vger.kernel.org, libc-alpha@sourceware.org,
        linux-api@vger.kernel.org, dhowells@redhat.com,
        David.Laight@aculab.com, zack@owlfolio.org, ltp@lists.linux.it,
        linux-man <linux-man@vger.kernel.org>
References: <20220621120355.2903-1-chrubis@suse.cz>
From:   Alejandro Colomar <alx.manpages@gmail.com>
In-Reply-To: <20220621120355.2903-1-chrubis@suse.cz>
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On 6/21/22 14:03, Cyril Hrubis wrote:
> This changes the __u64 and __s64 in userspace on 64bit platforms from
> long long (unsigned) int to just long (unsigned) int in order to match
> the uint64_t and int64_t size in userspace for C code.
> 
> We cannot make the change for C++ since that would be non-backwards
> compatible change and may cause possible regressions and even
> compilation failures, e.g. overloaded function may no longer find a
> correct match.
> 
> This allows us to use the kernel structure definitions in userspace in C
> code. For example we can use PRIu64 and PRId64 modifiers in printf() to
> print structure membere. Morever with this there would be no need to
> redefine these structures in an libc implementations as it is done now.
> 
> Consider for example the newly added statx() syscall. If we use the
> header from uapi we will get warnings when attempting to print it's
> members as:
> 
> 	printf("%" PRIu64 "\n", stx.stx_size);
> 
> We get:
> 
> 	warning: format '%lu' expects argument of type 'long unsigned int',
> 	         but argument 5 has type '__u64' {aka 'long long unsigned int'}
> 
> Signed-off-by: Cyril Hrubis <chrubis@suse.cz>

Acked-by: Alejandro Colomar <alx.manpages@gmail.com>

> ---
>   include/uapi/asm-generic/types.h | 11 +++++++++--
>   1 file changed, 9 insertions(+), 2 deletions(-)
> 
> v2: Make sure we do not break C++ applications
> v3: Update commit message to explain C++ exclusion
> 
> diff --git a/include/uapi/asm-generic/types.h b/include/uapi/asm-generic/types.h
> index dfaa50d99d8f..11e468a39d1e 100644