#10169: Fix argument parsing in socket.sendto() to avoid error masking.

3 files changed, 56 insertions, 5 deletions

diff --git a/Lib/test/test_socket.py b/Lib/test/test_socket.py
index d41bca51b5..7ee16ebced 100644
--- a/Lib/test/test_socket.py
+++ b/Lib/test/test_socket.py
@@ -274,6 +274,45 @@ class GeneralModuleTests(unittest.TestCase):
         self.assertRaises(socket.error, raise_gaierror,
                               "Error raising socket exception.")
 
+    def testSendtoErrors(self):
+        # Testing that sendto doens't masks failures. See #10169.
+        s = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
+        self.addCleanup(s.close)
+        s.bind(('', 0))
+        sockname = s.getsockname()
+        # 2 args
+        with self.assertRaises(UnicodeEncodeError):
+            s.sendto(u'\u2620', sockname)
+        with self.assertRaises(TypeError) as cm:
+            s.sendto(5j, sockname)
+        self.assertIn('not complex', str(cm.exception))
+        with self.assertRaises(TypeError) as cm:
+            s.sendto('foo', None)
+        self.assertIn('not NoneType', str(cm.exception))
+        # 3 args
+        with self.assertRaises(UnicodeEncodeError):
+            s.sendto(u'\u2620', 0, sockname)
+        with self.assertRaises(TypeError) as cm:
+            s.sendto(5j, 0, sockname)
+        self.assertIn('not complex', str(cm.exception))
+        with self.assertRaises(TypeError) as cm:
+            s.sendto('foo', 0, None)
+        self.assertIn('not NoneType', str(cm.exception))
+        with self.assertRaises(TypeError) as cm:
+            s.sendto('foo', 'bar', sockname)
+        self.assertIn('an integer is required', str(cm.exception))
+        with self.assertRaises(TypeError) as cm:
+            s.sendto('foo', None, None)
+        self.assertIn('an integer is required', str(cm.exception))
+        # wrong number of args
+        with self.assertRaises(TypeError) as cm:
+            s.sendto('foo')
+        self.assertIn('(1 given)', str(cm.exception))
+        with self.assertRaises(TypeError) as cm:
+            s.sendto('foo', 0, sockname, 4)
+        self.assertIn('(4 given)', str(cm.exception))
+
+
     def testCrucialConstants(self):
         # Testing for mission critical constants
         socket.AF_INET
diff --git a/Misc/NEWS b/Misc/NEWS
index 8c760576a6..8f3c0b9ab1 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -358,6 +358,8 @@ Library
 Extension Modules
 -----------------
 
+- Issue #10169: Fix argument parsing in socket.sendto() to avoid error masking.
+
 - Issue #12017: Fix segfault in json.loads() while decoding highly-nested
   objects using the C accelerations.
 
diff --git a/Modules/socketmodule.c b/Modules/socketmodule.c
index d14910a613..96b83b1150 100644
--- a/Modules/socketmodule.c
+++ b/Modules/socketmodule.c
@@ -2826,14 +2826,24 @@ sock_sendto(PySocketSockObject *s, PyObject *args)
     Py_ssize_t len;
     sock_addr_t addrbuf;
     int addrlen, n = -1, flags, timeout;
+    int arglen;
 
     flags = 0;
-    if (!PyArg_ParseTuple(args, "s*O:sendto", &pbuf, &addro)) {
-        PyErr_Clear();
-        if (!PyArg_ParseTuple(args, "s*iO:sendto",
-                              &pbuf, &flags, &addro))
-            return NULL;
+    arglen = PyTuple_Size(args);
+    switch(arglen) {
+        case 2:
+            PyArg_ParseTuple(args, "s*O:sendto", &pbuf, &addro);
+            break;
+        case 3:
+            PyArg_ParseTuple(args, "s*iO:sendto", &pbuf, &flags, &addro);
+            break;
+        default:
+            PyErr_Format(PyExc_TypeError, "sendto() takes 2 or 3"
+                         " arguments (%d given)", arglen);
     }
+    if (PyErr_Occurred())
+        return NULL;
+
     buf = pbuf.buf;
     len = pbuf.len;