[PATCH] string/stratcliff.c: Replace int with size_t [BZ #21982]

[Stefan Liebler]

On 08/22/2017 01:05 AM, H.J. Lu wrote:
> On Mon, Aug 21, 2017 at 8:41 AM, Stefan Liebler <stli@linux.vnet.ibm.com> wrote:
>> On 08/21/2017 04:53 PM, H.J. Lu wrote:
>>>
>>> On Mon, Aug 21, 2017 at 6:48 AM, Stefan Liebler <stli@linux.vnet.ibm.com>
>>> wrote:
>>>>
>>>> On 08/20/2017 07:17 PM, H.J. Lu wrote:
>>>>>
>>>>>
>>>>> Fix GCC 7 errors when string/stratcliff.c is compiled with -O3:
>>>>>
>>>>> stratcliff.c: In function ‘do_test’:
>>>>> cc1: error: assuming signed overflow does not occur when assuming that
>>>>> (X
>>>>> - c) <= X is always true [-Werror=strict-overflow]
>>>>>
>>>>> OK for master?
>>>>>
>>>>> H.J.
>>>>> ---
>>>>>           [BZ #21982]
>>>>>           * string/stratcliff.c (do_test): Declare size, nchars, inner,
>>>>>           middle and outer with size_t instead of int.  Repleace %d with
>>>>>           %Zd in printf.
>>>>> ---
>>>>>     string/stratcliff.c | 72
>>>>> ++++++++++++++++++++++++++---------------------------
>>>>>     1 file changed, 36 insertions(+), 36 deletions(-)
>>>>>
>>>>> diff --git a/string/stratcliff.c b/string/stratcliff.c
>>>>> index e28b0c5058..ae780379cb 100644
>>>>> --- a/string/stratcliff.c
>>>>> +++ b/string/stratcliff.c
>>>>> @@ -58,8 +58,8 @@
>>>>>     int
>>>>>     do_test (void)
>>>>>     {
>>>>> -  int size = sysconf (_SC_PAGESIZE);
>>>>> -  int nchars = size / sizeof (CHAR);
>>>>> +  size_t size = sysconf (_SC_PAGESIZE);
>>>>> +  size_t nchars = size / sizeof (CHAR);
>>>>>       CHAR *adr;
>>>>>       CHAR *dest;
>>>>>       int result = 0;
>>>>> @@ -80,7 +80,7 @@ do_test (void)
>>>>>         }
>>>>>       else
>>>>>         {
>>>>> -      int inner, middle, outer;
>>>>> +      size_t inner, middle, outer;
>>>>>
>>>>>           mprotect (adr, size, PROT_NONE);
>>>>>           mprotect (adr + 2 * nchars, size, PROT_NONE);
>>>>> @@ -101,7 +101,7 @@ do_test (void)
>>>>>
>>>>>                 if (STRLEN (&adr[outer]) != (size_t) (inner - outer))
>>>>>                   {
>>>>> -                 printf ("%s flunked for outer = %d, inner = %d\n",
>>>>> +                 printf ("%s flunked for outer = %Zd, inner = %Zd\n",
>>>>>                             STRINGIFY (STRLEN), outer, inner);
>>>>>                     result = 1;
>>>>>                   }
>>>>>                   {
>>>>> -                 printf ("%s flunked for outer = %d, middle = %d\n",
>>>>> +                 printf ("%s flunked for outer = %Zd, middle = %Zd\n",
>>>>>                             STRINGIFY (rawmemchr), outer, middle);
>>>>>                     result = 1;
>>>>>                   }
>>>>> Hi H.J. Lu,
>>>>
>>>>
>>>>
>>>> I've applied your patch and the warnings does not occur anymore on s390.
>>>
>>>
>>> Great.
>>>
>>>> The outer loops of the string tests are all using the following:
>>>> size_t nchars, outer;
>>>> for (outer = nchars - 1; outer >= MAX (0, nchars - 128); --outer)
>>>>
>>>> I think we can assume, that nchars is always > 128 as it is derived by
>>>> the
>>>> pagesize.
>>>> But if nchars would be equal to 128, this would result in an infinite
>>>> loop
>>>> (outer >= 0)?
>>>> If nchars would be less than 128, the tests would be skipped.
>>>>
>>>> Should we add a check that nchars > 128 at the beginning and replace the
>>>> "MAX (0, nchars - 128)" with only "nchars - 128"?
>>>
>>>
>>> This is a separate issue beyond BZ #21982.
>>>
>>>
>> Your patch is introducing this behaviour.
>> Before your patch, nchars and outer was an int and the for-loop-condition
>> "outer >= MAX (0, nchars - 128)" does not lead to an infinite loop or to
>> skipping the test if nchars <= 128.
>>
> 
> How about this patch?
> 
This solves the cases if nchars < 128.
But if nchars == 128, then the condition of the for-loop is "size_t 
outer >= 0", which is always true.

Could we check once if nchars > 128 and exit the test with an error if 
nchars is <= 128?
Are there architectures where the page size is < 4096?
Or where wchar_t > 4byte?

Bye
Stefan