Adding cleanup from @jagerman

Author: henryiii

include/pybind11/cast.h

@@ -981,18 +981,11 @@ struct type_caster<T, enable_if_t<std::is_arithmetic<T>::value && !is_std_char_t
         if (std::is_floating_point<T>::value) {
             return PyFloat_FromDouble((double) src);
         } else if (sizeof(T) <= sizeof(ssize_t)) {
-#if PY_VERSION_HEX < 0x03000000
             // This returns a long automatically if needed
             if (std::is_signed<T>::value)
-                return PyInt_FromSsize_t((ssize_t) src);
+                return PYBIND11_LONG_FROM_SIGNED(src);
             else
-                return PyInt_FromSize_t((size_t) src);
-#else
-            if (std::is_signed<T>::value)
-                return PyLong_FromSsize_t((ssize_t) src);
-            else
-                return PyLong_FromSize_t((size_t) src);
-#endif
+                return PYBIND11_LONG_FROM_UNSIGNED(src);
         } else {
             if (std::is_signed<T>::value)
                 return PyLong_FromLongLong((long long) src);

include/pybind11/detail/common.h

@@ -158,6 +158,8 @@
 #define PYBIND11_BYTES_SIZE PyBytes_Size
 #define PYBIND11_LONG_CHECK(o) PyLong_Check(o)
 #define PYBIND11_LONG_AS_LONGLONG(o) PyLong_AsLongLong(o)
+#define PYBIND11_LONG_FROM_SIGNED(o) PyLong_FromSsize_t((ssize_t) o)
+#define PYBIND11_LONG_FROM_UNSIGNED(o) PyLong_FromSize_t((size_t) o)
 #define PYBIND11_BYTES_NAME "bytes"
 #define PYBIND11_STRING_NAME "str"
 #define PYBIND11_SLICE_OBJECT PyObject
@@ -180,6 +182,8 @@
 #define PYBIND11_BYTES_SIZE PyString_Size
 #define PYBIND11_LONG_CHECK(o) (PyInt_Check(o) || PyLong_Check(o))
 #define PYBIND11_LONG_AS_LONGLONG(o) (PyInt_Check(o) ? (long long) PyLong_AsLong(o) : PyLong_AsLongLong(o))
+#define PYBIND11_LONG_FROM_SIGNED(o) PyInt_FromSsize_t((ssize_t) o) // Returns long if needed.
+#define PYBIND11_LONG_FROM_UNSIGNED(o) PyInt_FromSize_t((size_t) o) // Returns long if needed.
 #define PYBIND11_BYTES_NAME "str"
 #define PYBIND11_STRING_NAME "unicode"
 #define PYBIND11_SLICE_OBJECT PySliceObject

tests/test_builtin_casters.py

@@ -326,7 +326,11 @@ def test_numpy_bool():
 
 
 def test_int_long():
-    """In Python 2, a C++ int should return a Python int if possible, not long."""
+    """In Python 2, a C++ int should return a Python int rather than long
+    if possible: longs are not always accepted where ints are used (such
+    as the argument to sys.exit()). A C++ long long is always a Python
+    long."""
+
     import sys
     must_be_long = type(getattr(sys, 'maxint', 1) + 1)
     isinstance(m.int_cast(), int)