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

[H.J. Lu]

On Tue, Aug 22, 2017 at 5:07 AM, Stefan Liebler <stli@linux.vnet.ibm.com> wrote:
> 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?
>

Here is the updated patch.  I added

 if (outer == 0)
   break;

at the end of loop.

-- 
H.J.
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