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

[H.J. Lu]

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?

-- 
H.J.
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