*: NULL -> nil (Pyx and only where we can)

Convert Pyx part of the project to use nil instead of NULL.

Not every usage of NULL was converted and some places were left to use
NULL where changing it to nil currently hits Cython compilation error:

https://github.com/cython/cython/issues/3314

golang/_context.pyx

 # -*- coding: utf-8 -*-
 # cython: language_level=2
-# Copyright (C) 2019  Nexedi SA and Contributors.
-#                     Kirill Smelkov <kirr@nexedi.com>
+# Copyright (C) 2019-2020  Nexedi SA and Contributors.
+#                          Kirill Smelkov <kirr@nexedi.com>
 #
 # This program is free software: you can Use, Study, Modify and Redistribute
 # it under the terms of the GNU General Public License version 3, or (at your
@@ -58,7 +58,7 @@ cdef class PyContext:
             raise AssertionError("Context must not be instantiated by user")
 
     def __dealloc__(PyContext pyctx):
-        ctx = NULL
+        ctx = nil
 
     # deadline() returns context deadline or None, if there is no deadline.
     def deadline(PyContext pyctx):  # -> time | None

golang/_golang.pyx

@@ -5,7 +5,7 @@
 # distutils: language = c++
 # distutils: depends = libgolang.h
 #
-# Copyright (C) 2018-2019  Nexedi SA and Contributors.
+# Copyright (C) 2018-2020  Nexedi SA and Contributors.
 #                          Kirill Smelkov <kirr@nexedi.com>
 #
 # This program is free software: you can Use, Study, Modify and Redistribute
@@ -66,7 +66,7 @@ cdef void topyexc() except *:
     # recover_ is declared `except +` - if it was another - not panic -
     # exception, it will be converted to py exc by cython automatically.
     arg = recover_()
-    if arg != NULL:
+    if arg != nil:
         pyarg = <bytes>arg
         if PY_MAJOR_VERSION >= 3:
             pyarg = pyarg.decode("utf-8")
@@ -188,7 +188,7 @@ cdef class pychan:
         return pynil(parse_dtype(dtype))
 
     def __dealloc__(pychan pych):
-        if pych._ch == NULL:
+        if pych._ch == nil:
             return
 
         # pychan[X!=object]: just decref the raw chan and we are done.
@@ -264,7 +264,7 @@ cdef class pychan:
         cdef PyObject *_rxpy
         if pych.dtype == DTYPE_PYOBJECT:
             _rxpy = (<PyObject **>&_rx)[0]
-            if _rxpy != NULL:
+            if _rxpy != nil:
                 # we received the object and the channel dropped pointer to it.
                 rx = <object>_rxpy
                 Py_DECREF(rx)
@@ -287,7 +287,7 @@ cdef class pychan:
         return _chanlen_pyexc(pych._ch)
 
     def __repr__(pychan pych):
-        if pych._ch == NULL:
+        if pych._ch == nil:
             if pych.dtype == DTYPE_PYOBJECT:
                 return "nilchan"
             else:
@@ -309,7 +309,7 @@ cdef class pychan:
         # if one of the sides is nil[*] (untyped nil).
         if a.dtype == b.dtype:
             return True
-        if a._ch != NULL:
+        if a._ch != nil:
             return False
         if a.dtype == DTYPE_PYOBJECT or b.dtype == DTYPE_PYOBJECT:
             return True
@@ -425,7 +425,7 @@ def pyselect(*pycasev):
                     pypanic("pyselect: send expected: %r" % (pysend,))
 
                 tx = <object>(_tcase.ob_item[1])
-                casev[i] = _selsend(pych._ch, NULL)
+                casev[i] = _selsend(pych._ch, nil)
                 casev[i].flags = _INPLACE_DATA
                 casev[i].user  = pych.dtype
 
@@ -481,17 +481,17 @@ def pyselect(*pycasev):
     cdef PyObject *_rxpy
     cdef DType rxtype = <DType>casev[selected].user
     if rxtype == DTYPE_PYOBJECT:
-        # we received NULL or the object; if it is object, corresponding channel
+        # we received nil or the object; if it is object, corresponding channel
         # dropped pointer to it (see pychan.recv_ for details).
         _rxpy = (<PyObject **>&_rx)[0]
-        if _rxpy != NULL:
+        if _rxpy != nil:
             rx = <object>_rxpy
             Py_DECREF(rx)
 
     else:
         rx = c_to_py(rxtype, &_rx)
 
-    if casev[selected].rxok != NULL:
+    if casev[selected].rxok != nil:
         return selected, (rx, rxok)
     else:
         return selected, rx
@@ -522,8 +522,8 @@ cdef void _init_libgolang() except*:
     runtimecaps = (runtimemod + ".libgolang_runtime_ops").encode("utf-8") # py3
     cdef const _libgolang_runtime_ops *runtime_ops = \
         <const _libgolang_runtime_ops*>PyCapsule_Import(runtimecaps, 0)
-    if runtime_ops == NULL:
-        pypanic("init: %s: libgolang_runtime_ops=NULL" % runtimemod)
+    if runtime_ops == nil:
+        pypanic("init: %s: libgolang_runtime_ops=nil" % runtimemod)
     _libgolang_init(runtime_ops)
 
 

golang/_golang_test.pyx

@@ -2,7 +2,7 @@
 # cython: language_level=2
 # distutils: language=c++
 #
-# Copyright (C) 2018-2019  Nexedi SA and Contributors.
+# Copyright (C) 2018-2020  Nexedi SA and Contributors.
 #                          Kirill Smelkov <kirr@nexedi.com>
 #
 # This program is free software: you can Use, Study, Modify and Redistribute
@@ -38,11 +38,11 @@ cdef extern from "golang/libgolang.h" namespace "golang" nogil:
 
 # pylen_{recv,send}q returns len(_chan._{recv,send}q)
 def pylen_recvq(pychan pych not None): # -> int
-    if pych._ch == NULL:
+    if pych._ch == nil:
         raise AssertionError('len(.recvq) on nil channel')
     return _tchanrecvqlen(pych._ch)
 def pylen_sendq(pychan pych not None): # -> int
-    if pych._ch == NULL:
+    if pych._ch == nil:
         raise AssertionError('len(.sendq) on nil channel')
     return _tchansendqlen(pych._ch)
 
@@ -82,7 +82,7 @@ cdef class pypanicWhenBlocked:
         return t
 
     def __exit__(pypanicWhenBlocked t, typ, val, tb):
-        _tblockforever = NULL
+        _tblockforever = nil
 
 cdef void _panicblocked() nogil:
     panic("t: blocks forever")
@@ -158,12 +158,12 @@ def test_go_nogil():
 #   interfere with current py state )
 def test_runtime_vs_pyexc():
     cdef PyObject *pyexc
-    assert PyErr_Occurred() == NULL # no exception initially
+    assert PyErr_Occurred() == nil # no exception initially
 
     # set "current" exception
     PyErr_SetString(RuntimeError, "abc")
     pyexc = PyErr_Occurred()
-    assert pyexc != NULL
+    assert pyexc != nil
     assert pyexc == PyErr_Occurred()
 
     # makechan (also tests sema alloc)
@@ -193,7 +193,7 @@ def test_runtime_vs_pyexc():
 
     # clear current exception, or else test driver will see calling us as failure
     PyErr_Clear()
-    assert PyErr_Occurred() == NULL
+    assert PyErr_Occurred() == nil
 
 cdef void _noop() nogil:
     pass

golang/_sync.pyx

 # cython: language_level=2
-# Copyright (C) 2019  Nexedi SA and Contributors.
-#                     Kirill Smelkov <kirr@nexedi.com>
+# Copyright (C) 2019-2020  Nexedi SA and Contributors.
+#                          Kirill Smelkov <kirr@nexedi.com>
 #
 # This program is free software: you can Use, Study, Modify and Redistribute
 # it under the terms of the GNU General Public License version 3, or (at your
@@ -169,7 +169,7 @@ cdef class PyWorkGroup:
         pywg._pyctx = context.PyContext.from_ctx(_WorkGroup_ctx(pywg.wg._ptr()))
 
     def __dealloc__(PyWorkGroup pywg):
-        pywg.wg = NULL
+        pywg.wg = nil
 
     def go(PyWorkGroup pywg, f, *argv, **kw):
         # run f(._pyctx, ...) via _PyCtxFunc whose operator()(ctx)

golang/_sync_test.pyx

@@ -2,7 +2,7 @@
 # cython: language_level=2
 # distutils: language=c++
 #
-# Copyright (C) 2018-2019  Nexedi SA and Contributors.
+# Copyright (C) 2018-2020  Nexedi SA and Contributors.
 #                          Kirill Smelkov <kirr@nexedi.com>
 #
 # This program is free software: you can Use, Study, Modify and Redistribute
@@ -75,13 +75,13 @@ cdef nogil:
         cdef double Wstart, now
         while 1:
             i += 1
-            # wait till .sema != NULL and pop it
+            # wait till .sema != nil and pop it
             Wstart = time.now()
             j = 0
             while 1:
                 state.mu.lock()
                 sema = state.sema
-                if sema != NULL:
+                if sema != nil:
                     state.sema = NULL
                 stop = state.stop
                 state.mu.unlock()
@@ -89,7 +89,7 @@ cdef nogil:
                 if stop:
                     state.done.close()
                     return
-                if sema != NULL:
+                if sema != nil:
                     break
 
                 now = time.now()
@@ -109,8 +109,8 @@ cdef nogil:
 
     void _test_sema_wakeup() except +topyexc:
         cdef WorkState *state = <WorkState *>calloc(1, sizeof(WorkState))
-        if state == NULL:
-            panic("malloc -> NULL")
+        if state == nil:
+            panic("malloc -> nil")
         state.sema = NULL
         _mutex_init(&state.mu)
         state.stop = False

golang/_time.pyx

 # cython: language_level=2
-# Copyright (C) 2019  Nexedi SA and Contributors.
-#                     Kirill Smelkov <kirr@nexedi.com>
+# Copyright (C) 2019-2020  Nexedi SA and Contributors.
+#                          Kirill Smelkov <kirr@nexedi.com>
 #
 # This program is free software: you can Use, Study, Modify and Redistribute
 # it under the terms of the GNU General Public License version 3, or (at your
@@ -21,7 +21,7 @@
 
 from __future__ import print_function, absolute_import
 
-from golang cimport pychan, topyexc
+from golang cimport nil, pychan, topyexc
 from golang cimport sync
 from golang.pyx cimport runtime
 from cpython cimport PyObject
@@ -74,7 +74,7 @@ cdef class PyTicker:
         pytx.c = pychan.from_chan_double( pytx.tx.c )
 
     def __dealloc__(PyTicker pytx):
-        pytx.tx = NULL
+        pytx.tx = nil
 
     # stop cancels the ticker.
     #
@@ -104,7 +104,7 @@ cdef class PyTimer:
         pyt.c = pychan.from_chan_double( pyt.t.c )
 
     def __dealloc__(PyTimer pyt):
-        pyt.t = NULL
+        pyt.t = nil
 
     # stop cancels the timer.
     #