回复： Re: [PATCH linux-next] net/dccp/timer.c: use 'u64' instead of 's64' to avoid compiler's warning

[管雪涛 <gxt@pku.edu.cn>]

----- David Miller <davem@davemloft.net> 写道：
> From: Chen Gang <gang.chen.5i5j@gmail.com>
> Date: Wed, 21 May 2014 08:19:34 +0800
> 
> > 'dccp_timestamp_seed' is initialized once by ktime_get_real() in
> > dccp_timestamping_init(). It is always less than ktime_get_real()
> > in dccp_timestamp().
> > 
> > Then, ktime_us_delta() in dccp_timestamp() will always return positive
> > number. So can use manual type cast to let compiler and do_div() know
> > about it to avoid warning.
> > 
> > The related warning (with allmodconfig under unicore32):
> > 
> >     CC [M]  net/dccp/timer.o
> >   net/dccp/timer.c: In function ‘dccp_timestamp’:
> >   net/dccp/timer.c:285: warning: comparison of distinct pointer types lacks a cast
> > 
> > 
> > Signed-off-by: Chen Gang <gang.chen.5i5j@gmail.com>
> 
> Applied to net-next, thanks.
> 
> But that type check in include/asm-generic/div64.h is bogus, it should
> be checking sizeof(X) == 8 rather than the type thing, it just wants to
> make sure that the value is 64-bit regardless of it's signedness.
> 
> The arch local implementations do not do this, and that's why very few
> other people notice this warning.

Arch-dependent codes implement it with unsigned long long type.
And, every warning should not be ignored.