Add C API PyUnicode_FromOrdinal() which exposes unichr() at C level.

u'%c' will now raise a ValueError in case the argument is an
integer outside the valid range of Unicode code point ordinals.

Closes SF bug #593581.

Include/unicodeobject.h

@@ -517,6 +517,18 @@ extern DL_IMPORT(int) PyUnicode_AsWideChar(
 
 #endif
 
+/* --- Unicode ordinals --------------------------------------------------- */
+
+/* Create a Unicode Object from the given Unicode code point ordinal. 
+ 
+   The ordinal must be in range(0x10000) on narrow Python builds
+   (UCS2), and range(0x110000) on wide builds (UCS4). A ValueError is
+   raised in case it is not.
+
+*/
+
+extern DL_IMPORT(PyObject*) PyUnicode_FromOrdinal(int ordinal);
+
 /* === Builtin Codecs ===================================================== 
 
    Many of these APIs take two arguments encoding and errors. These

Lib/test/test_unicode.py

@@ -453,6 +453,14 @@ except KeyError:
 else:
     verify(value == u'abc, def')
 
+for ordinal in (-100, 0x20000):
+    try:
+        u"%c" % ordinal
+    except ValueError:
+        pass
+    else:
+        print '*** formatting u"%%c" % %i should give a ValueError' % ordinal
+
 # formatting jobs delegated from the string implementation:
 verify('...%(foo)s...' % {'foo':u"abc"} == u'...abc...')
 verify('...%(foo)s...' % {'foo':"abc"} == '...abc...')

Misc/NEWS

@@ -6,6 +6,9 @@ Type/class unification and new-style classes
 
 Core and builtins
 
+- u'%c' will now raise a ValueError in case the argument is an
+  integer outside the valid range of Unicode code point ordinals.
+
 - The tempfile module has been overhauled for enhanced security.  The
   mktemp() function is now deprecated; new, safe replacements are
   mkstemp() (for files) and mkdtemp() (for directories), and the
@@ -437,6 +440,9 @@ Build
 
 C API
 
+- New C API PyUnicode_FromOrdinal() which exposes unichr() at C
+  level.
+
 - New functions PyErr_SetExcFromWindowsErr() and
   PyErr_SetExcFromWindowsErrWithFilename(). Similar to
   PyErr_SetFromWindowsErrWithFilename() and

Objects/unicodeobject.c

@@ -390,6 +390,45 @@ int PyUnicode_AsWideChar(PyUnicodeObject *unicode,
 
 #endif
 
+PyObject *PyUnicode_FromOrdinal(int ordinal)
+{
+    Py_UNICODE s[2];
+
+#ifdef Py_UNICODE_WIDE
+    if (ordinal < 0 || ordinal > 0x10ffff) {
+	PyErr_SetString(PyExc_ValueError,
+			"unichr() arg not in range(0x110000) "
+			"(wide Python build)");
+	return NULL;
+    }
+#else
+    if (ordinal < 0 || ordinal > 0xffff) {
+	PyErr_SetString(PyExc_ValueError,
+			"unichr() arg not in range(0x10000) "
+			"(narrow Python build)");
+	return NULL;
+    }
+#endif
+
+    if (ordinal <= 0xffff) {
+	/* UCS-2 character */
+	s[0] = (Py_UNICODE) ordinal;
+	return PyUnicode_FromUnicode(s, 1);
+    }
+    else {
+#ifndef Py_UNICODE_WIDE
+	/* UCS-4 character.  store as two surrogate characters */
+	ordinal -= 0x10000L;
+	s[0] = 0xD800 + (Py_UNICODE) (ordinal >> 10);
+	s[1] = 0xDC00 + (Py_UNICODE) (ordinal & 0x03FF);
+	return PyUnicode_FromUnicode(s, 2);
+#else
+	s[0] = (Py_UNICODE)ordinal;
+	return PyUnicode_FromUnicode(s, 1);
+#endif
+    }
+}
+
 PyObject *PyUnicode_FromObject(register PyObject *obj)
 {
     /* XXX Perhaps we should make this API an alias of
@@ -5373,7 +5412,22 @@ formatchar(Py_UNICODE *buf,
 	x = PyInt_AsLong(v);
 	if (x == -1 && PyErr_Occurred())
 	    goto onError;
-	buf[0] = (char) x;
+#ifdef Py_UNICODE_WIDE
+	if (x < 0 || x > 0x10ffff) {
+	    PyErr_SetString(PyExc_ValueError,
+			    "%c arg not in range(0x110000) "
+			    "(wide Python build)");
+	    return -1;
+	}
+#else
+	if (x < 0 || x > 0xffff) {
+	    PyErr_SetString(PyExc_ValueError,
+			    "%c arg not in range(0x10000) "
+			    "(narrow Python build)");
+	    return -1;
+	}
+#endif
+	buf[0] = (Py_UNICODE) x;
     }
     buf[1] = '\0';
     return 1;

Python/bltinmodule.c

@@ -260,44 +260,11 @@ static PyObject *
 builtin_unichr(PyObject *self, PyObject *args)
 {
 	long x;
-	Py_UNICODE s[2];
 
 	if (!PyArg_ParseTuple(args, "l:unichr", &x))
 		return NULL;
 
-#ifdef Py_UNICODE_WIDE
-	if (x < 0 || x > 0x10ffff) {
-		PyErr_SetString(PyExc_ValueError,
-				"unichr() arg not in range(0x110000) "
-				"(wide Python build)");
-		return NULL;
-	}
-#else
-	if (x < 0 || x > 0xffff) {
-		PyErr_SetString(PyExc_ValueError,
-				"unichr() arg not in range(0x10000) "
-				"(narrow Python build)");
-		return NULL;
-	}
-#endif
-
-	if (x <= 0xffff) {
-		/* UCS-2 character */
-		s[0] = (Py_UNICODE) x;
-		return PyUnicode_FromUnicode(s, 1);
-	}
-	else {
-#ifndef Py_UNICODE_WIDE
-		/* UCS-4 character.  store as two surrogate characters */
-		x -= 0x10000L;
-		s[0] = 0xD800 + (Py_UNICODE) (x >> 10);
-		s[1] = 0xDC00 + (Py_UNICODE) (x & 0x03FF);
-		return PyUnicode_FromUnicode(s, 2);
-#else
-		s[0] = (Py_UNICODE)x;
-		return PyUnicode_FromUnicode(s, 1);
-#endif
-	}
+	return PyUnicode_FromOrdinal(x);
 }
 
 PyDoc_STRVAR(unichr_doc,