diff --git a/pandas/_libs/parsers.pyx b/pandas/_libs/parsers.pyx
index bbea66542a953..8f0f4e17df2f9 100644
--- a/pandas/_libs/parsers.pyx
+++ b/pandas/_libs/parsers.pyx
@@ -1406,59 +1406,6 @@ cdef inline StringPath _string_path(char *encoding):
 # Type conversions / inference support code
 
 
-cdef _string_box_factorize(parser_t *parser, int64_t col,
-                           int64_t line_start, int64_t line_end,
-                           bint na_filter, kh_str_starts_t *na_hashset):
-    cdef:
-        int error, na_count = 0
-        Py_ssize_t i, lines
-        coliter_t it
-        const char *word = NULL
-        ndarray[object] result
-
-        int ret = 0
-        kh_strbox_t *table
-
-        object pyval
-
-        object NA = na_values[np.object_]
-        khiter_t k
-
-    table = kh_init_strbox()
-    lines = line_end - line_start
-    result = np.empty(lines, dtype=np.object_)
-    coliter_setup(&it, parser, col, line_start)
-
-    for i in range(lines):
-        COLITER_NEXT(it, word)
-
-        if na_filter:
-            if kh_get_str_starts_item(na_hashset, word):
-                # in the hash table
-                na_count += 1
-                result[i] = NA
-                continue
-
-        k = kh_get_strbox(table, word)
-
-        # in the hash table
-        if k != table.n_buckets:
-            # this increments the refcount, but need to test
-            pyval = <object>table.vals[k]
-        else:
-            # box it. new ref?
-            pyval = PyBytes_FromString(word)
-
-            k = kh_put_strbox(table, word, &ret)
-            table.vals[k] = <PyObject*>pyval
-
-        result[i] = pyval
-
-    kh_destroy_strbox(table)
-
-    return result, na_count
-
-
 cdef _string_box_utf8(parser_t *parser, int64_t col,
                       int64_t line_start, int64_t line_end,
                       bint na_filter, kh_str_starts_t *na_hashset):
diff --git a/pandas/_libs/src/ujson/python/objToJSON.c b/pandas/_libs/src/ujson/python/objToJSON.c
index 48712dc68829d..21f439ec93e0f 100644
--- a/pandas/_libs/src/ujson/python/objToJSON.c
+++ b/pandas/_libs/src/ujson/python/objToJSON.c
@@ -399,22 +399,6 @@ static void *CLong(JSOBJ obj, JSONTypeContext *tc, void *outValue,
     return NULL;
 }
 
-#ifdef _LP64
-static void *PyIntToINT64(JSOBJ _obj, JSONTypeContext *tc, void *outValue,
-                          size_t *_outLen) {
-    PyObject *obj = (PyObject *)_obj;
-    *((JSINT64 *)outValue) = PyLong_AsLong(obj);
-    return NULL;
-}
-#else
-static void *PyIntToINT32(JSOBJ _obj, JSONTypeContext *tc, void *outValue,
-                          size_t *_outLen) {
-    PyObject *obj = (PyObject *)_obj;
-    *((JSINT32 *)outValue) = PyLong_AsLong(obj);
-    return NULL;
-}
-#endif
-
 static void *PyLongToINT64(JSOBJ _obj, JSONTypeContext *tc, void *outValue,
                            size_t *_outLen) {
     *((JSINT64 *)outValue) = GET_TC(tc)->longValue;
diff --git a/pandas/_libs/tslibs/nattype.pyx b/pandas/_libs/tslibs/nattype.pyx
index 3ddce28fb6dd1..a3274f74fff9e 100644
--- a/pandas/_libs/tslibs/nattype.pyx
+++ b/pandas/_libs/tslibs/nattype.pyx
@@ -95,10 +95,6 @@ cdef class _NaT(datetime):
     # higher than np.ndarray and np.matrix
     __array_priority__ = 100
 
-    def __hash__(_NaT self):
-        # py3k needs this defined here
-        return hash(self.value)
-
     def __richcmp__(_NaT self, object other, int op):
         cdef:
             int ndim = getattr(other, 'ndim', -1)
diff --git a/setup.py b/setup.py
index 545765ecb114d..a5c26b064f2f3 100755
--- a/setup.py
+++ b/setup.py
@@ -462,7 +462,7 @@ def run(self):
         extra_link_args.append("/DEBUG")
 else:
     # args to ignore warnings
-    extra_compile_args = ["-Wno-unused-function"]
+    extra_compile_args = []
     extra_link_args = []
     if debugging_symbols_requested:
         extra_compile_args.append("-g")