linux-kernel - Re: [PATCH 1/2] [CIFS] Fix signed/unsigned pointer warning

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Date:	Sat, 13 Dec 2014 23:20:06 -0600
From:	Steve French <smfrench@...il.com>
To:	Kevin Cernekee <cernekee@...il.com>
Cc:	Steve French <sfrench@...ba.org>,
	"linux-cifs@...r.kernel.org" <linux-cifs@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/2] [CIFS] Fix signed/unsigned pointer warning

Probably harmless patch - but I didn't notice the warning on x86
kernel build (building on Fedora 21, gcc 4.9.2)

On Fri, Dec 12, 2014 at 11:19 AM, Kevin Cernekee <cernekee@...il.com> wrote:
> On Mon, Nov 10, 2014 at 1:09 PM, Kevin Cernekee <cernekee@...il.com> wrote:
>> Commit 2ae83bf93882d1 ("[CIFS] Fix setting time before epoch (negative
>> time values)") changed "u64 t" to "s64 t", which makes do_div() complain
>> about a pointer signedness mismatch:
>>
>>       CC      fs/cifs/netmisc.o
>>     In file included from ./arch/mips/include/asm/div64.h:12:0,
>>                      from include/linux/kernel.h:124,
>>                      from include/linux/list.h:8,
>>                      from include/linux/wait.h:6,
>>                      from include/linux/net.h:23,
>>                      from fs/cifs/netmisc.c:25:
>>     fs/cifs/netmisc.c: In function ‘cifs_NTtimeToUnix’:
>>     include/asm-generic/div64.h:43:28: warning: comparison of distinct pointer types lacks a cast [enabled by default]
>>       (void)(((typeof((n)) *)0) == ((uint64_t *)0)); \
>>                                 ^
>>     fs/cifs/netmisc.c:941:22: note: in expansion of macro ‘do_div’
>>        ts.tv_nsec = (long)do_div(t, 10000000) * 100;
>>
>> Introduce a temporary "u64 abs_t" variable to fix this.
>>
>> Signed-off-by: Kevin Cernekee <cernekee@...il.com>
>> ---
>>  fs/cifs/netmisc.c | 12 +++++++-----
>>  1 file changed, 7 insertions(+), 5 deletions(-)
>>
>>
>> Note: this is compile-tested only (on a 32-bit build).
>>
>>
>> diff --git a/fs/cifs/netmisc.c b/fs/cifs/netmisc.c
>> index b333ff6..abae6dd 100644
>> --- a/fs/cifs/netmisc.c
>> +++ b/fs/cifs/netmisc.c
>> @@ -926,6 +926,7 @@ cifs_NTtimeToUnix(__le64 ntutc)
>>
>>         /* Subtract the NTFS time offset, then convert to 1s intervals. */
>>         s64 t = le64_to_cpu(ntutc) - NTFS_TIME_OFFSET;
>> +       u64 abs_t;
>>
>>         /*
>>          * Unfortunately can not use normal 64 bit division on 32 bit arch, but
>> @@ -933,13 +934,14 @@ cifs_NTtimeToUnix(__le64 ntutc)
>>          * to special case them
>>          */
>>         if (t < 0) {
>> -               t = -t;
>> -               ts.tv_nsec = (long)(do_div(t, 10000000) * 100);
>> +               abs_t = -t;
>> +               ts.tv_nsec = (long)(do_div(abs_t, 10000000) * 100);
>>                 ts.tv_nsec = -ts.tv_nsec;
>> -               ts.tv_sec = -t;
>> +               ts.tv_sec = -abs_t;
>>         } else {
>> -               ts.tv_nsec = (long)do_div(t, 10000000) * 100;
>> -               ts.tv_sec = t;
>> +               abs_t = t;
>> +               ts.tv_nsec = (long)do_div(abs_t, 10000000) * 100;
>> +               ts.tv_sec = abs_t;
>>         }
>>
>>         return ts;
>> --
>> 2.1.1
>>
>
> Hi guys,
>
> I am still seeing this warning on Linus' head of tree.  Do you think
> this is something we can pull in for 3.19?
>
> Thanks!



-- 
Thanks,

Steve
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