From mboxrd@z Thu Jan  1 00:00:00 1970
From: David Miller <davem@davemloft.net>
Subject: Re: [PATCH V1 net-next 2/4] net/mlx5_core: Use hardware registers
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Date: Wed, 01 Oct 2014 14:56:15 -0400 (EDT)
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From: Alexei Starovoitov <alexei.starovoitov@gmail.com>
Date: Wed, 1 Oct 2014 10:12:10 -0700

>> +#define MLX5_SET64(typ, p, fld, v) do { \
>> +       if (__mlx5_bit_sz(typ, fld) != 64) \
>> +               non_existent_function(); \
>> +       else if (__mlx5_bit_off(typ, fld) % 64) \
>> +               non_existent_function(); \
>> +       else \
>> +               *((__be64 *)(p) + __mlx5_64_off(typ, fld)) = cpu_to_be64(v); \
>> +} while (0)
> 
> is it possible to use BUILD_BUG_ON instead of runtime pr_info() ?

Indeed, please don't invent your own facilities for compile-time checks,
we have BUILD_BUG_ON() so please use it instead of non_existent_function()
which BTW doesn't work with some non-gcc compilers.