search.c: Fix build failure due new GCC

The warning by GCC is false positive because we don't access the freed memory in the scope, only the pointer memory which contained address of allocated memory on the heap, and used that for updating index pointer.

Using ptrdiff_t struct before realloc works the warning around.

cgi-bin/search.c

@@ -1,7 +1,7 @@
 /*
  * Search routines for CUPS.
  *
- * Copyright © 2020-2024 by OpenPrinting.
+ * Copyright © 2020-2025 by OpenPrinting.
  * Copyright © 2007-2018 by Apple Inc.
  * Copyright © 1997-2006 by Easy Software Products.
  *
@@ -169,26 +169,27 @@ cgiCompileSearch(const char *query)	/* I - Query string */
       if (wlen > slen)
       {
        /*
-        * Expand the RE string buffer...
+	* Expand the RE string buffer...
 	*/
 
-        char *temp;			/* Temporary string pointer */
+	char *temp;			/* Temporary string pointer */
+	const ptrdiff_t pos = sptr - s;	/* Current pointer position (GCC workaround for use-after-free warning after realloc) */
 
 
 	slen = wlen + 128;
-        temp = (char *)realloc(s, slen);
+	temp = (char *)realloc(s, slen);
 	if (!temp)
 	{
 	  free(s);
 	  free(re);
 
 	  if (lword)
-            free(lword);
+	    free(lword);
 
 	  return (NULL);
 	}
 
-        sptr = temp + (sptr - s);
+	sptr = temp + pos;
 	s    = temp;
       }