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

----- David Miller [off-list ref] 写道：

From: Chen Gang <redacted>
Date: Wed, 21 May 2014 08:19:34 +0800

quoted

'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 <redacted>

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.