Error on C Warnings

pandas/_libs/hashtable_class_helper.pxi.in

@@ -192,7 +192,7 @@ cdef class StringVector:
 
         append_data_string(self.data, x)
 
-    cdef extend(self, ndarray[:] x):
+    cdef extend(self, ndarray[object] x):
         for i in range(len(x)):
             self.append(x[i])
 
@@ -237,7 +237,7 @@ cdef class ObjectVector:
         self.external_view_exists = True
         return self.ao
 
-    cdef extend(self, ndarray[:] x):
+    cdef extend(self, ndarray[object] x):
         for i in range(len(x)):
             self.append(x[i])
 

pandas/_libs/internals.pyx

@@ -371,8 +371,8 @@ def get_blkno_indexers(int64_t[:] blknos, bint group=True):
         Py_ssize_t i, start, stop, n, diff
 
         object blkno
-        list group_order
-        dict group_dict
+        list group_order = []
+        dict group_dict = {}
         int64_t[:] res_view
 
     n = blknos.shape[0]
@@ -393,9 +393,6 @@ def get_blkno_indexers(int64_t[:] blknos, bint group=True):
 
         yield cur_blkno, slice(start, n)
     else:
-        group_order = []
-        group_dict = {}
-
         for i in range(1, n):
             if blknos[i] != cur_blkno:
                 if cur_blkno not in group_dict:

pandas/_libs/parsers.pyx

@@ -701,7 +701,7 @@ cdef class TextReader:
             char *word
             object name, old_name
             int status
-            uint64_t hr, data_line
+            uint64_t hr, data_line = 0
             char *errors = "strict"
             StringPath path = _string_path(self.c_encoding)
 
@@ -805,7 +805,6 @@ cdef class TextReader:
                 self._tokenize_rows(1)
 
             header = [ self.names ]
-            data_line = 0
 
             if self.parser.lines < 1:
                 field_count = len(header[0])

pandas/_libs/src/ujson/python/objToJSON.c

@@ -1454,7 +1454,7 @@ char **NpyArr_encodeLabels(PyArrayObject *labels, PyObjectEncoder *enc,
                                  1000000000LL; // nanoseconds per second
                 } else {
                     // datetime.* objects don't follow above rules
-                    nanosecVal = PyDateTimeToEpoch(item, NPY_FR_ns);
+                  nanosecVal = PyDateTimeToEpoch((PyDateTime_Date *)item, NPY_FR_ns);
                 }
             }
         }

pandas/_libs/writers.pyx

@@ -31,7 +31,7 @@ def write_csv_rows(list data, ndarray data_index,
     """
     # In crude testing, N>100 yields little marginal improvement
     cdef:
-        Py_ssize_t i, j, k = len(data_index), N = 100, ncols = len(cols)
+        Py_ssize_t i, j = 0, k = len(data_index), N = 100, ncols = len(cols)
         list rows
 
     # pre-allocate rows

pandas/io/sas/sas.pyx

@@ -120,7 +120,7 @@ cdef const uint8_t[:] rdc_decompress(int result_length, const uint8_t[:] inbuff)
 
     cdef:
         uint8_t cmd
-        uint16_t ctrl_bits, ctrl_mask = 0, ofs, cnt
+        uint16_t ctrl_bits = 0, ctrl_mask = 0, ofs, cnt
         int rpos = 0, k
         uint8_t[:] outbuff = np.zeros(result_length, dtype=np.uint8)
         Py_ssize_t ipos = 0, length = len(inbuff)

setup.py

@@ -433,8 +433,7 @@ def run(self):
         extra_compile_args.append("/Z7")
         extra_link_args.append("/DEBUG")
 else:
-    # args to ignore warnings
-    extra_compile_args = []
+    extra_compile_args = ["-Werror"]
     extra_link_args = []
     if debugging_symbols_requested:
         extra_compile_args.append("-g")
@@ -477,6 +476,14 @@ def run(self):
 #  we can't do anything about these warnings because they stem from
 #  cython+numpy version mismatches.
 macros.append(("NPY_NO_DEPRECATED_API", "0"))
+if "-Werror" in extra_compile_args:
+    try:
+        import numpy as np
+    except ImportError:
+        pass
+    else:
+        if np.__version__ < LooseVersion("1.16.0"):
+            extra_compile_args.remove("-Werror")
 
 
 # ----------------------------------------------------------------------