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SubjectRe: [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@gmail.com> wrote:
> On Mon, Nov 10, 2014 at 1:09 PM, Kevin Cernekee <cernekee@gmail.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@gmail.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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