ntdll: qsort: comparator must not get the same pointer.

dlls/ntdll/misc.c

@@ -272,7 +272,7 @@ NTDLL_mergesort( void *arr, void *barr, int elemsize, int(__cdecl *compar)(const
 
         for (k=left; k<=right; k++) {
             /*arr[k]=(barr[i]<barr[j])?barr[i++]:barr[j--];*/
-            if (compar(X(barr,i),X(barr,j))<0) {
+            if (i != j && compar(X(barr,i),X(barr,j))<0) {
                 memcpy(X(arr,k),X(barr,i),elemsize);
                 i++;
             } else {

dlls/ntdll/tests/string.c

@@ -1145,16 +1145,19 @@ static void test_wcsrchr(void)
 
 static __cdecl int intcomparefunc(const void *a, const void*b)
 {
+	ok (a != b, "must never get the same pointer\n");
 	return (*(int*)a) - (*(int*)b);
 }
 
 static __cdecl int charcomparefunc(const void *a, const void*b)
 {
+	ok (a != b, "must never get the same pointer\n");
 	return (*(char*)a) - (*(char*)b);
 }
 
 static __cdecl int strcomparefunc(const void *a, const void*b)
 {
+	ok (a != b, "must never get the same pointer\n");
 	return lstrcmpA(*(char**)a,*(char**)b);
 }