linux-kernel - Re: [PATCH] selftests: net: fix warning when compiling selftest/net

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Message-ID: <20220316202251.382b687e@kicinski-fedora-pc1c0hjn.dhcp.thefacebook.com>
Date:   Wed, 16 Mar 2022 20:22:51 -0700
From:   Jakub Kicinski <kuba@...nel.org>
To:     Guo Zhengkui <guozhengkui@...o.com>
Cc:     "David S. Miller" <davem@...emloft.net>,
        Shuah Khan <shuah@...nel.org>,
        netdev@...r.kernel.org (open list:NETWORKING [GENERAL]),
        linux-kselftest@...r.kernel.org (open list:KERNEL SELFTEST FRAMEWORK),
        linux-kernel@...r.kernel.org (open list),
        zhengkui_guo@...look.com
Subject: Re: [PATCH] selftests: net: fix warning when compiling selftest/net

On Wed, 16 Mar 2022 19:50:40 +0800 Guo Zhengkui wrote:
> When I compile tools/testing/selftests/net/ by
> `make -C tools/testing/selftests/net` with gcc (Debian 8.3.0-6) 8.3.0,
> it reports the following warnings:
> 
> txtimestamp.c: In function 'validate_timestamp':
> txtimestamp.c:164:29: warning: format '%lu' expects argument of type
> 'long unsigned int', but argument 3 has type 'int64_t'
> {aka 'long long int'} [-Wformat=]
>    fprintf(stderr, "ERROR: %lu us expected between %d and %d\n",
>                            ~~^
>                            %llu
>      cur64 - start64, min_delay, max_delay);
>      ~~~~~~~~~~~~~~~
> txtimestamp.c: In function '__print_ts_delta_formatted':
> txtimestamp.c:173:22: warning: format '%lu' expects argument of type
> 'long unsigned int', but argument 3 has type 'int64_t'
> {aka 'long long int'} [-Wformat=]
>    fprintf(stderr, "%lu ns", ts_delta);
>                     ~~^      ~~~~~~~~
>                     %llu
> txtimestamp.c:175:22: warning: format '%lu' expects argument of type
> 'long unsigned int', but argument 3 has type 'int64_t'
> {aka 'long long int'} [-Wformat=]
>    fprintf(stderr, "%lu us", ts_delta / NSEC_PER_USEC);
>                     ~~^
>                     %llu
> 
> `int64_t` is the alias for `long long int`. '%lld' is more suitable.

That's on 32bit machines, I think what you need to use is PRId64.
Or just cast the result / change variable types to long long.