Use correct signedness in wcsncmp

	[BZ #18206]
	* wcsmbs/wcsncmp.c (wcsncmp): Compare as wchar_t, not wint_t.
	  Use signed comparision instead of substraction to avoid
	  overflow bug.
	* localedata/tests-mbwc/tst_wcsncmp.c (tst_wcsncmp):
	  Take the sign of ret.
	* localedata/tests-mbwc/dat_wcsncmp.c (tst_wcsncmp_loc):
	  Do not expect precise return values. Only the sign matters.
	* wcsmbs/Makefile (strop-tests): Add wcsncmp.
	* wcsmbs/test-wcsncmp.c: New File.
	* string/test-strncmp.c: Add wcsncmp support.

3 files changed, 21 insertions, 19 deletions

diff --git a/wcsmbs/Makefile b/wcsmbs/Makefile
index 69f78922a2..44a4494403 100644
--- a/wcsmbs/Makefile
+++ b/wcsmbs/Makefile
@@ -42,7 +42,7 @@ routines := wcscat wcschr wcscmp wcscpy wcscspn wcsdup wcslen wcsncat \
 	    isoc99_swscanf isoc99_vswscanf \
 	    mbrtoc16 c16rtomb
 
-strop-tests :=  wcscmp wmemcmp wcslen wcschr wcsrchr wcscpy
+strop-tests :=  wcscmp wcsncmp wmemcmp wcslen wcschr wcsrchr wcscpy
 tests := tst-wcstof wcsmbs-tst1 tst-wcsnlen tst-btowc tst-mbrtowc \
 	 tst-wcrtomb tst-wcpncpy tst-mbsrtowcs tst-wchar-h tst-mbrtowc2 \
 	 tst-c16c32-1 wcsatcliff $(addprefix test-,$(strop-tests))
diff --git a/wcsmbs/test-wcsncmp.c b/wcsmbs/test-wcsncmp.c
new file mode 100644
index 0000000000..07757d8e45
--- /dev/null
+++ b/wcsmbs/test-wcsncmp.c
@@ -0,0 +1,2 @@
+#define WIDE 1
+#include "../string/test-strncmp.c"
diff --git a/wcsmbs/wcsncmp.c b/wcsmbs/wcsncmp.c
index 59e003b857..e083ad8174 100644
--- a/wcsmbs/wcsncmp.c
+++ b/wcsmbs/wcsncmp.c
@@ -29,42 +29,42 @@ wcsncmp (s1, s2, n)
      const wchar_t *s2;
      size_t n;
 {
-  wint_t c1 = L'\0';
-  wint_t c2 = L'\0';
+  wchar_t c1 = L'\0';
+  wchar_t c2 = L'\0';
 
   if (n >= 4)
     {
       size_t n4 = n >> 2;
       do
 	{
-	  c1 = (wint_t) *s1++;
-	  c2 = (wint_t) *s2++;
+	  c1 = *s1++;
+	  c2 = *s2++;
 	  if (c1 == L'\0' || c1 != c2)
-	    return c1 - c2;
-	  c1 = (wint_t) *s1++;
-	  c2 = (wint_t) *s2++;
+	    return c1 > c2 ? 1 : (c1 < c2 ? -1 : 0);
+	  c1 = *s1++;
+	  c2 = *s2++;
 	  if (c1 == L'\0' || c1 != c2)
-	    return c1 - c2;
-	  c1 = (wint_t) *s1++;
-	  c2 = (wint_t) *s2++;
+	    return c1 > c2 ? 1 : (c1 < c2 ? -1 : 0);
+	  c1 = *s1++;
+	  c2 = *s2++;
 	  if (c1 == L'\0' || c1 != c2)
-	    return c1 - c2;
-	  c1 = (wint_t) *s1++;
-	  c2 = (wint_t) *s2++;
+	    return c1 > c2 ? 1 : (c1 < c2 ? -1 : 0);
+	  c1 = *s1++;
+	  c2 = *s2++;
 	  if (c1 == L'\0' || c1 != c2)
-	    return c1 - c2;
+	    return c1 > c2 ? 1 : (c1 < c2 ? -1 : 0);
 	} while (--n4 > 0);
       n &= 3;
     }
 
   while (n > 0)
     {
-      c1 = (wint_t) *s1++;
-      c2 = (wint_t) *s2++;
+      c1 = *s1++;
+      c2 = *s2++;
       if (c1 == L'\0' || c1 != c2)
-	return c1 - c2;
+	return c1 > c2 ? 1 : (c1 < c2 ? -1 : 0);
       n--;
     }
 
-  return c1 - c2;
+  return 0;
 }