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