*: NULL/nullptr -> nil (C++ only)

Convert C++ part of the project to use nil instead of NULL/nullptr.

We do not convert pyx part yet, because Cython currently does not
understand that nullptr_t has properties of NULL and with e.g. the
following change

    --- a/golang/_context.pyx
    +++ b/golang/_context.pyx
    @@ -116,7 +116,7 @@ cdef cppclass _PyValue (_interface, gobject) nogil:
         __dealloc__():
             with gil:
                 obj = <object>this.pyobj
    -            this.pyobj = NULL
    +            this.pyobj = nil
                 Py_DECREF(obj)

errors as

    Error compiling Cython file:
    ------------------------------------------------------------
    ...
            if __decref():
                del self
        __dealloc__():
            with gil:
                obj = <object>this.pyobj
                this.pyobj = nil
                            ^
    ------------------------------------------------------------

    golang/_context.pyx:119:25: Cannot assign type 'nullptr_t' to 'PyObject *'

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

golang/context.cpp

-// Copyright (C) 2019  Nexedi SA and Contributors.
+// 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
@@ -53,9 +53,9 @@ struct _Background final : _Context, object {
     }
 
     double          deadline()              { return INFINITY;  }
-    chan<structZ>   done()                  { return NULL;      }
-    error           err()                   { return NULL;      }
-    interface       value(const void *key)  { return NULL;      }
+    chan<structZ>   done()                  { return nil;       }
+    error           err()                   { return nil;       }
+    interface       value(const void *key)  { return nil;       }
 };
 
 static Context _background = adoptref(static_cast<_Context *>(new _Background()));
@@ -98,7 +98,7 @@ struct _BaseCtx : _Context, object {
         // chan: if context can be canceled on its own
         // nil:  if context can not be canceled on its own
         ctx._done       = done;
-        if (done == NULL) {
+        if (done == nil) {
             if (parentv.size() != 1)
                 panic("BUG: _BaseCtx: done==nil, but len(parentv) != 1");
         }
@@ -109,7 +109,7 @@ struct _BaseCtx : _Context, object {
     chan<structZ> done() {
         _BaseCtx& ctx = *this;
 
-        if (ctx._done != NULL)
+        if (ctx._done != nil)
             return ctx._done;
         return ctx._parentv[0]->done();
     }
@@ -130,10 +130,10 @@ struct _BaseCtx : _Context, object {
 
         for (auto parent : ctx._parentv) {
             interface v = parent->value(key);
-            if (v != NULL)
+            if (v != nil)
                 return v;
         }
-        return NULL;
+        return nil;
     }
 
     double deadline() {
@@ -152,7 +152,7 @@ struct _BaseCtx : _Context, object {
     // _cancel cancels ctx and its children.
     void _cancel(error err) {
         _BaseCtx& ctx = *this;
-        return ctx._cancelFrom(NULL, err);
+        return ctx._cancelFrom(nil, err);
     }
 
     // _cancelFrom cancels ctx and its children.
@@ -162,7 +162,7 @@ struct _BaseCtx : _Context, object {
 
         set<refptr<_BaseCtx>> children;
         ctx._mu.lock();
-            if (ctx._err != NULL) {
+            if (ctx._err != nil) {
                 ctx._mu.unlock();
                 return; // already canceled
             }
@@ -171,7 +171,7 @@ struct _BaseCtx : _Context, object {
             ctx._children.swap(children);
         ctx._mu.unlock();
 
-        if (ctx._done != NULL)
+        if (ctx._done != nil)
             ctx._done.close();
 
         // no longer need to propagate cancel from parent after we are canceled
@@ -180,7 +180,7 @@ struct _BaseCtx : _Context, object {
             if (parent == cancelFrom)
                 continue;
             _BaseCtx *_parent = dynamic_cast<_BaseCtx *>(parent._ptr());
-            if (_parent != NULL) {
+            if (_parent != nil) {
                 _parent->_mu.lock();
                     _parent->_children.erase(bctx);
                 _parent->_mu.unlock();
@@ -204,14 +204,14 @@ struct _BaseCtx : _Context, object {
             // if parent can never be canceled (e.g. it is background) - we
             // don't need to propagate cancel from it.
             chan<structZ> pdone = parent->done();
-            if (pdone == NULL)
+            if (pdone == nil)
                 continue;
 
             // parent is cancellable - glue to propagate cancel from it to us
             _BaseCtx *_parent = dynamic_cast<_BaseCtx *>(parent._ptr());
-            if (_parent != NULL) {
+            if (_parent != nil) {
                 _parent->_mu.lock();
-                    if (_parent->_err != NULL)
+                    if (_parent->_err != nil)
                         ctx._cancel(_parent->_err);
                     else
                         _parent->_children.insert(bctx);
@@ -259,7 +259,7 @@ struct _ValueCtx : _BaseCtx {
     interface   _value;
 
     _ValueCtx(const void *key, interface value, Context parent)
-            : _BaseCtx(NULL, {parent}) {
+            : _BaseCtx(nil, {parent}) {
         _ValueCtx& ctx = *this;
 
         ctx._key   = key;
@@ -363,7 +363,7 @@ static bool _ready(chan<structZ> ch) {
 // _tctxchildren returns context's children, assuming context is instance of _BaseCtx.
 set<Context> _tctxchildren(Context ctx) {
     _BaseCtx *_bctx = dynamic_cast<_BaseCtx*>(ctx._ptr());
-    if (_bctx == NULL)
+    if (_bctx == nil)
         panic("context is not instance of golang.context._BaseCtx");
 
     set<Context> children;

golang/fmt.cpp

-// Copyright (C) 2019  Nexedi SA and Contributors.
+// 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
@@ -38,7 +38,7 @@ string _vsprintf(const char *format, va_list argp) {
     // based on https://stackoverflow.com/a/26221725/9456786
     va_list argp2;
     va_copy(argp2, argp);
-    size_t nchar = ::vsnprintf(NULL, 0, format, argp2);
+    size_t nchar = ::vsnprintf(nil, 0, format, argp2);
     va_end(argp2);
 
     std::unique_ptr<char[]> buf( new char[nchar /*for \0*/+1] );

golang/libgolang.h

@@ -412,14 +412,14 @@ class chan {
     _chan *_ch;
 
 public:
-    inline chan() { _ch = NULL; } // nil channel if not explicitly initialized
+    inline chan() { _ch = nil; } // nil channel if not explicitly initialized
     friend chan<T> makechan<T>(unsigned size);
     friend chan<T> _wrapchan<T>(_chan *_ch);
-    inline ~chan() { _chanxdecref(_ch); _ch = NULL; }
+    inline ~chan() { _chanxdecref(_ch); _ch = nil; }
 
     // = nil
-    inline chan(nullptr_t) { _ch = NULL; }
-    inline chan& operator=(nullptr_t) { _chanxdecref(_ch); _ch = NULL; return *this; }
+    inline chan(nullptr_t) { _ch = nil; }
+    inline chan& operator=(nullptr_t) { _chanxdecref(_ch); _ch = nil; return *this; }
     // copy
     inline chan(const chan& from) { _ch = from._ch; _chanxincref(_ch); }
     inline chan& operator=(const chan& from) {
@@ -429,10 +429,10 @@ public:
         return *this;
     }
     // move
-    inline chan(chan&& from) { _ch = from._ch; from._ch = NULL; }
+    inline chan(chan&& from) { _ch = from._ch; from._ch = nil; }
     inline chan& operator=(chan&& from) {
         if (this != &from) {
-            _chanxdecref(_ch); _ch = from._ch; from._ch = NULL;
+            _chanxdecref(_ch); _ch = from._ch; from._ch = nil;
         }
         return *this;
     }
@@ -457,7 +457,7 @@ public:
     //
     // if pok is provided the case is extended to `[*prx, *pok] = ch.recv_()`
     // if both prx and pok are omitted the case is reduced to `ch.recv()`.
-    [[nodiscard]] inline _selcase recvs(T *prx=NULL, bool *pok=NULL) const {
+    [[nodiscard]] inline _selcase recvs(T *prx=nil, bool *pok=nil) const {
         return _selrecv_(_ch, prx, pok);
     }
 
@@ -466,8 +466,8 @@ public:
     inline unsigned cap()             const  { return _chancap(_ch); }
 
     // compare wrt nil
-    inline bool operator==(nullptr_t) const  { return (_ch == NULL); }
-    inline bool operator!=(nullptr_t) const  { return (_ch != NULL); }
+    inline bool operator==(nullptr_t) const  { return (_ch == nil); }
+    inline bool operator!=(nullptr_t) const  { return (_ch != nil); }
 
     // compare wrt chan
     inline bool operator==(const chan<T>& ch2) const { return (_ch == ch2._ch); }
@@ -494,7 +494,7 @@ chan<T> makechan(unsigned size) {
 }
 
 // _wrapchan<T> wraps raw channel with chan<T>.
-// raw channel must be either NULL or its element size must correspond to T.
+// raw channel must be either nil or its element size must correspond to T.
 LIBGOLANG_API void __wrapchan(_chan *_ch, unsigned elemsize);
 template<typename T> static inline
 chan<T> _wrapchan(_chan *_ch) {
@@ -577,36 +577,36 @@ class refptr {
 
 public:
     // nil if not explicitly initialized
-    inline refptr()                 { _obj = NULL;  }
+    inline refptr()                 { _obj = nil;  }
 
     inline ~refptr() {
-        if (_obj != NULL) {
+        if (_obj != nil) {
             _obj->decref();
-            _obj = NULL;
+            _obj = nil;
         }
     }
 
     // = nil
-    inline refptr(nullptr_t)        { _obj = NULL;  }
+    inline refptr(nullptr_t)        { _obj = nil;  }
     inline refptr& operator=(nullptr_t) {
-        if (_obj != NULL)
+        if (_obj != nil)
             _obj->decref();
-        _obj = NULL;
+        _obj = nil;
         return *this;
     }
 
     // copy
     inline refptr(const refptr& from) {
         _obj = from._obj;
-        if(_obj != NULL)
+        if (_obj != nil)
             _obj->incref();
     }
     inline refptr& operator=(const refptr& from) {
         if (this != &from) {
-            if (_obj != NULL)
+            if (_obj != nil)
                 _obj->decref();
             _obj = from._obj;
-            if (_obj != NULL)
+            if (_obj != nil)
                 _obj->incref();
         }
         return *this;
@@ -615,14 +615,14 @@ public:
     // move
     inline refptr(refptr&& from) {
         _obj = from._obj;
-        from._obj = NULL;
+        from._obj = nil;
     }
     inline refptr& operator=(refptr&& from) {
         if (this != &from) {
-            if (_obj != NULL)
+            if (_obj != nil)
                 _obj->decref();
             _obj = from._obj;
-            from._obj = NULL;
+            from._obj = nil;
         }
         return *this;
     }
@@ -632,8 +632,8 @@ public:
     friend refptr<T> newref<T>  (T *_obj);
 
     // compare wrt nil
-    inline bool operator==(nullptr_t) const { return (_obj == NULL);    }
-    inline bool operator!=(nullptr_t) const { return (_obj != NULL);    }
+    inline bool operator==(nullptr_t) const { return (_obj == nil); }
+    inline bool operator!=(nullptr_t) const { return (_obj != nil); }
 
     // compare wrt refptr
     inline bool operator==(const refptr& p2) const { return (_obj == p2._obj);  }
@@ -681,21 +681,21 @@ public:
     }
 
     // nil if not explicitly initialized
-    inline global()                 { _obj = NULL;  }
+    inline global()                 { _obj = nil;   }
 
     // init from refptr<T>
     inline global(const refptr<T>& from) {
         _obj = from._obj;
-        if (_obj != NULL)
+        if (_obj != nil)
             _obj->incref();
     }
 
     // = nil
-    inline global(nullptr_t)        { _obj = NULL;  }
+    inline global(nullptr_t)        { _obj = nil;   }
     inline global& operator=(nullptr_t) {
-        if (_obj != NULL)
+        if (_obj != nil)
             _obj->decref();
-        _obj = NULL;
+        _obj = nil;
         return *this;
     }
 
@@ -703,8 +703,8 @@ public:
     // move - no need due to refptr<T> cast
 
     // compare wrt nil
-    inline bool operator==(nullptr_t) const { return (_obj == NULL);    }
-    inline bool operator!=(nullptr_t) const { return (_obj != NULL);    }
+    inline bool operator==(nullptr_t) const { return (_obj == nil); }
+    inline bool operator!=(nullptr_t) const { return (_obj != nil); }
 
     // compare wrt refptr
     inline bool operator==(const refptr<T>& p2) const { return (_obj == p2._obj);  }
@@ -747,7 +747,7 @@ template<typename T>
 inline refptr<T> newref(T *_obj) {
     refptr<T> p;
     p._obj = _obj;
-    if (_obj != NULL)
+    if (_obj != nil)
         _obj->incref();
     return p;
 }

golang/runtime/libgolang_test.cpp

-// Copyright (C) 2019  Nexedi SA and Contributors.
+// 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
@@ -46,14 +46,14 @@ using std::vector;
 // verify chan<T> automatic reference counting.
 void _test_chan_cpp_refcount() {
     chan<int> ch;
-    ASSERT(ch == NULL);
-    ASSERT(!(ch != NULL));
-    ASSERT(ch._rawchan() == NULL);
+    ASSERT(ch == nil);
+    ASSERT(!(ch != nil));
+    ASSERT(ch._rawchan() == nil);
 
     ch = makechan<int>();
-    ASSERT(!(ch == NULL));
-    ASSERT(ch != NULL);
-    ASSERT(ch._rawchan() != NULL);
+    ASSERT(!(ch == nil));
+    ASSERT(ch != nil);
+    ASSERT(ch._rawchan() != nil);
     _chan *_ch = ch._rawchan();
     ASSERT(_chanrefcnt(_ch) == 1);
 
@@ -71,8 +71,8 @@ void _test_chan_cpp_refcount() {
     // copy =
     {
         chan<int> ch2;
-        ASSERT(ch2 == NULL);
-        ASSERT(ch2._rawchan() == NULL);
+        ASSERT(ch2 == nil);
+        ASSERT(ch2._rawchan() == nil);
 
         ch2 = ch;
         ASSERT(ch2._rawchan() == _ch);
@@ -80,9 +80,9 @@ void _test_chan_cpp_refcount() {
         ASSERT(ch2 == ch);
         ASSERT(!(ch2 != ch));
 
-        ch2 = NULL;
-        ASSERT(ch2 == NULL);
-        ASSERT(ch2._rawchan() == NULL);
+        ch2 = nil;
+        ASSERT(ch2 == nil);
+        ASSERT(ch2._rawchan() == nil);
         ASSERT(_chanrefcnt(_ch) == 1);
         ASSERT(!(ch2 == ch));
         ASSERT(ch2 != ch);
@@ -91,18 +91,18 @@ void _test_chan_cpp_refcount() {
 
     // move ctor
     chan<int> ch2(move(ch));
-    ASSERT(ch == NULL);
-    ASSERT(ch._rawchan() == NULL);
-    ASSERT(ch2 != NULL);
+    ASSERT(ch == nil);
+    ASSERT(ch._rawchan() == nil);
+    ASSERT(ch2 != nil);
     ASSERT(ch2._rawchan() == _ch);
     ASSERT(_chanrefcnt(_ch) == 1);
 
     // move =
     ch = move(ch2);
-    ASSERT(ch != NULL);
+    ASSERT(ch != nil);
     ASSERT(ch._rawchan() == _ch);
-    ASSERT(ch2 == NULL);
-    ASSERT(ch2._rawchan() == NULL);
+    ASSERT(ch2 == nil);
+    ASSERT(ch2._rawchan() == nil);
     ASSERT(_chanrefcnt(_ch) == 1);
 
     // ch goes out of scope and destroys raw channel
@@ -117,7 +117,7 @@ struct Point {
 void _test_chan_cpp() {
     chan<structZ> done = makechan<structZ>();
     chan<int>     chi  = makechan<int>(1);
-    chan<Point>   chp  = makechan<Point>(); chp = NULL;
+    chan<Point>   chp  = makechan<Point>(); chp = nil;
 
     int   i, j, _;
     Point p;
@@ -155,7 +155,7 @@ void _test_chan_cpp() {
 // waitBlocked waits until at least nrx recv and ntx send operations block
 // waiting on the channel.
 void waitBlocked(_chan *ch, int nrx, int ntx) {
-    if (ch == NULL)
+    if (ch == nil)
         panic("wait blocked: called on nil channel");
 
     double t0 = time::now();
@@ -308,12 +308,12 @@ void __test_close_wakeup_all(bool vs_select) {
         // as other workers vvv don't use ch after wakeup from ch.recv().
         if (!vs_select)
             ASSERT(_chanrefcnt(ch._rawchan()) == 1);
-        ch = NULL;
+        ch = nil;
         done.send(structZ{});
     });
     waitBlocked(_ch, /*nrx=*/1, /*ntx=*/0);
     ASSERT(_chanrefcnt(_ch) == 2);
-    ch = NULL;
+    ch = nil;
     ASSERT(_chanrefcnt(_ch) == 1);
 
     // many other ch.recv or select({ch.recv}) subscribers queued to ch.recvq
@@ -321,7 +321,7 @@ void __test_close_wakeup_all(bool vs_select) {
     for (i=0; i < N; i++) {
         go([_ch, done, vs_select]() {
             if (!vs_select) {
-                _chanrecv(_ch, NULL);
+                _chanrecv(_ch, nil);
             } else {
                 int rx;
                 select({
@@ -363,7 +363,7 @@ void __test_select_win_while_queue() {
 
     Data *data_send = (Data *)calloc(1, sizeof(Data));
     Data *data_recv = (Data *)calloc(1, sizeof(Data));
-    if (data_send == NULL || data_recv == NULL)
+    if (data_send == nil || data_recv == nil)
         throw std::bad_alloc();
     for (i=0; i<Ndata; i++)
         data_send->_[i] = i % 0xff;
@@ -407,7 +407,7 @@ void _test_select_inplace() {
     // inplace tx
     go([ch]() {
         _selcase sel[1];
-        sel[0] = ch.sends(NULL);
+        sel[0] = ch.sends(nil);
         *(int *)&sel[0].itxrx = 12345;
         sel[0].flags = _INPLACE_DATA;
         int _ = select(sel);
@@ -421,34 +421,34 @@ void _test_select_inplace() {
     _selcase sel[1];
     sel[0] = ch.recvs();
     sel[0].flags = _INPLACE_DATA;
-    const char *err = NULL;
+    const char *err = nil;
     try {
         select(sel);
     } catch (...) {
         err = recover();
     }
-    ASSERT(err != NULL);
+    ASSERT(err != nil);
     ASSERT(!strcmp(err, "select: recv into inplace data"));
 
     // _selcase ptx/prx
     _selcase cas = _default;
 
-    err = NULL;
+    err = nil;
     try {
         cas.ptx();
     } catch (...) {
         err = recover();
     }
-    ASSERT(err != NULL);
+    ASSERT(err != nil);
     ASSERT(!strcmp(err, "_selcase: ptx: op != send"));
 
-    err = NULL;
+    err = nil;
     try {
         cas.prx();
     } catch (...) {
         err = recover();
     }
-    ASSERT(err != NULL);
+    ASSERT(err != nil);
     ASSERT(!strcmp(err, "_selcase: prx: op != recv"));
 
     cas = ch.sends(&i);
@@ -459,13 +459,13 @@ void _test_select_inplace() {
     cas = ch.recvs(&i);
     ASSERT(cas.prx() == &i);
     cas.flags = _INPLACE_DATA;
-    err = NULL;
+    err = nil;
     try {
         cas.prx();
     } catch (...) {
         err = recover();
     }
-    ASSERT(err != NULL);
+    ASSERT(err != nil);
     ASSERT(!strcmp(err, "_selcase: prx: recv with inplace data"));
 }
 
@@ -501,9 +501,9 @@ public:
 
 void _test_refptr() {
     refptr<MyObj> p;
-    ASSERT(p == NULL);
-    ASSERT(!(p != NULL));
-    ASSERT(p._ptr() == NULL);
+    ASSERT(p == nil);
+    ASSERT(!(p != nil));
+    ASSERT(p._ptr() == nil);
 
     MyObj *obj = new MyObj();
     ASSERT(obj->refcnt() == 1);
@@ -551,8 +551,8 @@ void _test_refptr() {
     {
         refptr<MyObj> q;
         ASSERT(obj->refcnt() == 1);
-        ASSERT(q == NULL);
-        ASSERT(q._ptr() == NULL);
+        ASSERT(q == nil);
+        ASSERT(q._ptr() == nil);
         ASSERT(!(p == q));
         ASSERT(p != q);
 
@@ -563,10 +563,10 @@ void _test_refptr() {
         ASSERT(p == q);
         ASSERT(!(p != q));
 
-        q = NULL;
+        q = nil;
         ASSERT(obj->refcnt() == 1);
         ASSERT(p._ptr() == obj);
-        ASSERT(q._ptr() == NULL);
+        ASSERT(q._ptr() == nil);
         ASSERT(!(p == q));
         ASSERT(p != q);
     }
@@ -575,34 +575,34 @@ void _test_refptr() {
     // move ctor
     refptr<MyObj> q(move(p));
     ASSERT(obj->refcnt() == 1);
-    ASSERT(p == NULL);
-    ASSERT(p._ptr() == NULL);
-    ASSERT(q != NULL);
+    ASSERT(p == nil);
+    ASSERT(p._ptr() == nil);
+    ASSERT(q != nil);
     ASSERT(q._ptr() == obj);
 
     // move =
     p = move(q);
     ASSERT(obj->refcnt() == 1);
-    ASSERT(p != NULL);
+    ASSERT(p != nil);
     ASSERT(p._ptr() == obj);
-    ASSERT(q == NULL);
-    ASSERT(q._ptr() == NULL);
+    ASSERT(q == nil);
+    ASSERT(q._ptr() == nil);
 
     // p goes out of scope and destroys obj
 }
 
 void _test_global() {
     global<refptr<MyObj>> g;
-    ASSERT(g == NULL);
-    ASSERT(!(g != NULL));
-    ASSERT(g._ptr() == NULL);
+    ASSERT(g == nil);
+    ASSERT(!(g != nil));
+    ASSERT(g._ptr() == nil);
 
     MyObj *obj = new MyObj();
     refptr<MyObj> p = adoptref(obj);
     ASSERT(obj->refcnt() == 1);
     obj->i = 3;
 
-    ASSERT(g._ptr() == NULL);
+    ASSERT(g._ptr() == nil);
     ASSERT(p._ptr() == obj);
     ASSERT(!(g == p));
     ASSERT(!(p == g));
@@ -614,8 +614,8 @@ void _test_global() {
     ASSERT(obj->refcnt() == 2);
     ASSERT(g._ptr() == obj);
     ASSERT(p._ptr() == obj);
-    ASSERT(!(g == NULL));
-    ASSERT(g != NULL);
+    ASSERT(!(g == nil));
+    ASSERT(g != nil);
     ASSERT(g == p);
     ASSERT(p == g);
     ASSERT(!(g != p));
@@ -630,15 +630,15 @@ void _test_global() {
 
     // global = nil     - obj reference is released
     ASSERT(obj->refcnt() == 2);
-    g = NULL;
+    g = nil;
     ASSERT(obj->refcnt() == 1);
-    ASSERT(g._ptr() == NULL);
+    ASSERT(g._ptr() == nil);
 
     // copy ctor    global <- refptr
     {
         global<refptr<MyObj>> h(p);
         ASSERT(obj->refcnt() == 2);
-        ASSERT(g._ptr() == NULL);
+        ASSERT(g._ptr() == nil);
         ASSERT(h._ptr() == obj);
         ASSERT(p._ptr() == obj);
         ASSERT(!(h == g));

golang/runtime/libpyxruntime.cpp

-// Copyright (C) 2019  Nexedi SA and Contributors.
+// 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
@@ -39,8 +39,8 @@ namespace runtime {
 
 
 // pyexited indicates whether Python interpreter exited.
-static sync::Mutex     *pyexitedMu  = NULL; // allocated in _init and never freed not to race
-static sync::WaitGroup *pygilTaking = NULL; // at exit on dtor vs use.
+static sync::Mutex     *pyexitedMu  = nil; // allocated in _init and never freed not to race
+static sync::WaitGroup *pygilTaking = nil; // at exit on dtor vs use.
 static bool            pyexited = false;
 
 void _init() {
@@ -102,8 +102,8 @@ error PyErr_Fetch() {
     PyGILState_Release(gstate);
 
     // no error
-    if (pyexc_type == NULL && pyexc_value == NULL && pyexc_tb == NULL)
-        return NULL;
+    if (pyexc_type == nil && pyexc_value == nil && pyexc_tb == nil)
+        return nil;
 
     // -> _PyError
     _PyError* _e = new _PyError();
@@ -141,9 +141,9 @@ _PyError::~_PyError() {
     PyObject *pyexc_type    = this->pyexc_type;
     PyObject *pyexc_value   = this->pyexc_value;
     PyObject *pyexc_tb      = this->pyexc_tb;
-    this->pyexc_type  = NULL;
-    this->pyexc_value = NULL;
-    this->pyexc_tb    = NULL;
+    this->pyexc_type  = nil;
+    this->pyexc_value = nil;
+    this->pyexc_tb    = nil;
     if (!ok) {
         return;
     }
@@ -182,7 +182,7 @@ PyFunc::PyFunc(const PyFunc& from) {
 
     tie(gstate, ok) = pygil_ensure();
     if (!ok) {
-        pyf = NULL; // won't be used
+        pyf = nil; // won't be used
         return;
     }
 
@@ -197,7 +197,7 @@ PyFunc::~PyFunc() {
 
     tie(gstate, ok) = pygil_ensure();
     PyObject *pyf = this->pyf;
-    this->pyf = NULL;
+    this->pyf = nil;
     if (!ok) {
         return;
     }
@@ -222,8 +222,8 @@ error PyFunc::operator() () const {
     }
 
         error err;
-        PyObject *ret = PyObject_CallFunction(pyf, NULL);
-        if (ret == NULL) {
+        PyObject *ret = PyObject_CallFunction(pyf, nil);
+        if (ret == nil) {
             err = PyErr_Fetch();
         }
         Py_XDECREF(ret);

golang/sync.cpp

-// 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
@@ -84,13 +84,13 @@ void WaitGroup::add(int delta) {
 void WaitGroup::wait() {
     WaitGroup& wg = *this;
 
-    chan<structZ> done = NULL;
+    chan<structZ> done = nil;
     wg._mu.lock();
     if (wg._count != 0)
         done = wg._done;
     wg._mu.unlock();
 
-    if (done == NULL)   // wg._count was =0
+    if (done == nil)    // wg._count was =0
         return;
 
     done.recv();
@@ -123,7 +123,7 @@ void _WorkGroup::go(func<error(context::Context)> f) {
         });
 
         error err = f(g->_ctx); // TODO consider also propagating panic
-        if (err == NULL)
+        if (err == nil)
             return;
 
         g->_mu.lock();
@@ -131,7 +131,7 @@ void _WorkGroup::go(func<error(context::Context)> f) {
             g->_mu.unlock();
         });
 
-        if (g->_err == NULL) {
+        if (g->_err == nil) {
             // this goroutine is the first failed task
             g->_err = err;
             g->_cancel();

golang/time.cpp

-// Copyright (C) 2019  Nexedi SA and Contributors.
+// 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
@@ -39,7 +39,7 @@ Timer  _new_timer(double dt, func<void()>);
 
 chan<double> tick(double dt) {
     if (dt <= 0)
-        return NULL;
+        return nil;
     return new_ticker(dt)->c;
 }
 
@@ -120,7 +120,7 @@ void _Timer::decref() {
 
 Timer _new_timer(double dt, func<void()> f) {
     Timer t = adoptref(new _Timer());
-    t->c    = (f == NULL ? makechan<double>(1) : NULL);
+    t->c    = (f == nil ? makechan<double>(1) : nil);
     t->_f   = f;
     t->_dt  = INFINITY;
     t->_ver = 0;
@@ -129,7 +129,7 @@ Timer _new_timer(double dt, func<void()> f) {
 }
 
 Timer new_timer(double dt) {
-    return _new_timer(dt, NULL);
+    return _new_timer(dt, nil);
 }
 
 bool _Timer::stop() {
@@ -186,7 +186,7 @@ void _Timer::_fire(double dt, int ver) {
 
     // send under ._mu so that .stop can be sure that if it sees
     // ._dt = INFINITY, there is no ongoing .c send.
-    if (t._f == NULL) {
+    if (t._f == nil) {
         t.c.send(now());
         t._mu.unlock();
         return;