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


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


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