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

[Stefan Liebler]

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.

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"?

Bye,
Stefan