Issue #18184: PyUnicode_FromFormat() and PyUnicode_FromFormatV() now raise

OverflowError when an argument of %c format is out of range.

Lib/test/test_unicode.py

@@ -2048,6 +2048,8 @@ class UnicodeTest(string_tests.CommonTest,
                      b'%c', c_int(0xabcd))
         check_format('\U0010ffff',
                      b'%c', c_int(0x10ffff))
+        with self.assertRaises(OverflowError):
+            PyUnicode_FromFormat(b'%c', c_int(0x110000))
         # Issue #18183
         check_format('\U00010000\U00100000',
                      b'%c%c', c_int(0x10000), c_int(0x100000))

Misc/NEWS

@@ -10,6 +10,9 @@ What's New in Python 3.4.0 Alpha 1?
 Core and Builtins
 -----------------
 
+- Issue #18184: PyUnicode_FromFormat() and PyUnicode_FromFormatV() now raise
+  OverflowError when an argument of %c format is out of range.
+
 - Issue #18137: Detect integer overflow on precision in float.__format__()
   and complex.__format__().
 

Objects/unicodeobject.c

@@ -2496,7 +2496,7 @@ unicode_fromformat_arg(_PyUnicodeWriter *writer,
     {
         int ordinal = va_arg(*vargs, int);
         if (ordinal < 0 || ordinal > MAX_UNICODE) {
-            PyErr_SetString(PyExc_ValueError,
+            PyErr_SetString(PyExc_OverflowError,
                             "character argument not in range(0x110000)");
             return NULL;
         }