bpo-6532: Make the thread id an unsigned integer. (python#781)

* bpo-6532: Make the thread id an unsigned integer.

From C API side the type of results of PyThread_start_new_thread() and
PyThread_get_thread_ident(), the id parameter of
PyThreadState_SetAsyncExc(), and the thread_id field of PyThreadState
changed from "long" to "unsigned long".

* Restore a check in thread_get_ident().

Doc/c-api/init.rst

@@ -830,7 +830,7 @@ been created.
    the caller should assume no current thread state is available.
 
 
-.. c:function:: int PyThreadState_SetAsyncExc(long id, PyObject *exc)
+.. c:function:: int PyThreadState_SetAsyncExc(unsigned long id, PyObject *exc)
 
    Asynchronously raise an exception in a thread. The *id* argument is the thread
    id of the target thread; *exc* is the exception object to be raised. This
@@ -840,6 +840,9 @@ been created.
    zero if the thread id isn't found.  If *exc* is :const:`NULL`, the pending
    exception (if any) for the thread is cleared. This raises no exceptions.
 
+   .. versionchanged:: 3.7
+      The type of the *id* parameter changed from :c:type:`long` to
+      :c:type:`unsigned long`.
 
 .. c:function:: void PyEval_AcquireThread(PyThreadState *tstate)
 

Doc/whatsnew/3.7.rst

@@ -185,6 +185,16 @@ Deprecated
   (Contributed by Serhiy Storchaka in :issue:`28692`.)
 
 
+Changes in the C API
+--------------------
+
+- The type of results of :c:func:`PyThread_start_new_thread` and
+  :c:func:`PyThread_get_thread_ident`, and the *id* parameter of
+  :c:func:`PyThreadState_SetAsyncExc` changed from :c:type:`long` to
+  :c:type:`unsigned long`.
+  (Contributed by Serhiy Storchaka in :issue:`6532`.)
+
+
 Removed
 =======
 

Include/pystate.h

@@ -108,7 +108,7 @@ typedef struct _ts {
     int gilstate_counter;
 
     PyObject *async_exc; /* Asynchronous exception to raise */
-    long thread_id; /* Thread id where this tstate was created */
+    unsigned long thread_id; /* Thread id where this tstate was created */
 
     int trash_delete_nesting;
     PyObject *trash_delete_later;
@@ -200,7 +200,7 @@ PyAPI_FUNC(PyThreadState *) _PyThreadState_UncheckedGet(void);
 
 PyAPI_FUNC(PyThreadState *) PyThreadState_Swap(PyThreadState *);
 PyAPI_FUNC(PyObject *) PyThreadState_GetDict(void);
-PyAPI_FUNC(int) PyThreadState_SetAsyncExc(long, PyObject *);
+PyAPI_FUNC(int) PyThreadState_SetAsyncExc(unsigned long, PyObject *);
 
 
 /* Variable and macro for in-line access to current thread state */

Include/pythread.h

@@ -17,10 +17,14 @@ typedef enum PyLockStatus {
     PY_LOCK_INTR
 } PyLockStatus;
 
+#ifndef Py_LIMITED_API
+#define PYTHREAD_INVALID_THREAD_ID ((unsigned long)-1)
+#endif
+
 PyAPI_FUNC(void) PyThread_init_thread(void);
-PyAPI_FUNC(long) PyThread_start_new_thread(void (*)(void *), void *);
+PyAPI_FUNC(unsigned long) PyThread_start_new_thread(void (*)(void *), void *);
 PyAPI_FUNC(void) PyThread_exit_thread(void);
-PyAPI_FUNC(long) PyThread_get_thread_ident(void);
+PyAPI_FUNC(unsigned long) PyThread_get_thread_ident(void);
 
 PyAPI_FUNC(PyThread_type_lock) PyThread_allocate_lock(void);
 PyAPI_FUNC(void) PyThread_free_lock(PyThread_type_lock);

Lib/_dummy_thread.py

@@ -69,7 +69,7 @@ def get_ident():
     available, it is safe to assume that the current process is the
     only thread.  Thus a constant can be safely returned.
     """
-    return -1
+    return 1
 
 def allocate_lock():
     """Dummy implementation of _thread.allocate_lock()."""

Lib/test/test_dummy_thread.py

@@ -111,8 +111,7 @@ def test_exit(self):
     def test_ident(self):
         self.assertIsInstance(_thread.get_ident(), int,
                               "_thread.get_ident() returned a non-integer")
-        self.assertNotEqual(_thread.get_ident(), 0,
-                        "_thread.get_ident() returned 0")
+        self.assertGreater(_thread.get_ident(), 0)
 
     def test_LockType(self):
         self.assertIsInstance(_thread.allocate_lock(), _thread.LockType,

Lib/test/test_sys.py

@@ -393,6 +393,9 @@ def g456():
         thread_id = thread_info[0]
 
         d = sys._current_frames()
+        for tid in d:
+            self.assertIsInstance(tid, int)
+            self.assertGreater(tid, 0)
 
         main_id = threading.get_ident()
         self.assertIn(main_id, d)

Lib/test/test_threading.py

@@ -181,6 +181,7 @@ def test_PyThreadState_SetAsyncExc(self):
         ctypes = import_module("ctypes")
 
         set_async_exc = ctypes.pythonapi.PyThreadState_SetAsyncExc
+        set_async_exc.argtypes = (ctypes.c_ulong, ctypes.py_object)
 
         class AsyncExc(Exception):
             pass
@@ -189,9 +190,11 @@ class AsyncExc(Exception):
 
         # First check it works when setting the exception from the same thread.
         tid = threading.get_ident()
+        self.assertIsInstance(tid, int)
+        self.assertGreater(tid, 0)
 
         try:
-            result = set_async_exc(ctypes.c_long(tid), exception)
+            result = set_async_exc(tid, exception)
             # The exception is async, so we might have to keep the VM busy until
             # it notices.
             while True:
@@ -237,7 +240,7 @@ def run(self):
         # Try a thread id that doesn't make sense.
         if verbose:
             print("    trying nonsensical thread id")
-        result = set_async_exc(ctypes.c_long(-1), exception)
+        result = set_async_exc(-1, exception)
         self.assertEqual(result, 0)  # no thread states modified
 
         # Now raise an exception in the worker thread.
@@ -250,7 +253,7 @@ def run(self):
         self.assertFalse(t.finished)
         if verbose:
             print("    attempting to raise asynch exception in worker")
-        result = set_async_exc(ctypes.c_long(t.id), exception)
+        result = set_async_exc(t.id, exception)
         self.assertEqual(result, 1) # one thread state modified
         if verbose:
             print("    waiting for worker to say it caught the exception")

Lib/threading.py

@@ -993,14 +993,14 @@ def _delete(self):
         #
         # Must take care to not raise an exception if _dummy_thread is being
         # used (and thus this module is being used as an instance of
-        # dummy_threading).  _dummy_thread.get_ident() always returns -1 since
+        # dummy_threading).  _dummy_thread.get_ident() always returns 1 since
         # there is only one thread if _dummy_thread is being used.  Thus
         # len(_active) is always <= 1 here, and any Thread instance created
         # overwrites the (if any) thread currently registered in _active.
         #
         # An instance of _MainThread is always created by 'threading'.  This
         # gets overwritten the instant an instance of Thread is created; both
-        # threads return -1 from _dummy_thread.get_ident() and thus have the
+        # threads return 1 from _dummy_thread.get_ident() and thus have the
         # same key in the dict.  So when the _MainThread instance created by
         # 'threading' tries to clean itself up when atexit calls this method
         # it gets a KeyError if another Thread instance was created.

Misc/NEWS

@@ -813,6 +813,10 @@ Windows
 C API
 -----
 
+- bpo-6532: The type of results of PyThread_start_new_thread() and
+  PyThread_get_thread_ident(), and the id parameter of
+  PyThreadState_SetAsyncExc() changed from "long" to "unsigned long".
+
 - Issue #27867: Function PySlice_GetIndicesEx() is deprecated and replaced with
   a macro if Py_LIMITED_API is not set or set to the value between 0x03050400
   and 0x03060000 (not including) or 0x03060100 or higher.  Added functions

Modules/_io/bufferedio.c

@@ -239,7 +239,7 @@ typedef struct {
 
 #ifdef WITH_THREAD
     PyThread_type_lock lock;
-    volatile long owner;
+    volatile unsigned long owner;
 #endif
 
     Py_ssize_t buffer_size;

Modules/_multiprocessing/semaphore.c

@@ -14,7 +14,7 @@ enum { RECURSIVE_MUTEX, SEMAPHORE };
 typedef struct {
     PyObject_HEAD
     SEM_HANDLE handle;
-    long last_tid;
+    unsigned long last_tid;
     int count;
     int maxvalue;
     int kind;

Modules/_sqlite/connection.c

@@ -1125,7 +1125,7 @@ int pysqlite_check_thread(pysqlite_Connection* self)
         if (PyThread_get_thread_ident() != self->thread_ident) {
             PyErr_Format(pysqlite_ProgrammingError,
                         "SQLite objects created in a thread can only be used in that same thread."
-                        "The object was created in thread id %ld and this is thread id %ld",
+                        "The object was created in thread id %lu and this is thread id %lu",
                         self->thread_ident, PyThread_get_thread_ident());
             return 0;
         }

Modules/_sqlite/connection.h

@@ -61,7 +61,7 @@ typedef struct
     int initialized;
 
     /* thread identification of the thread the connection was created in */
-    long thread_ident;
+    unsigned long thread_ident;
 
     pysqlite_Cache* statement_cache;
 

Modules/_ssl.c

@@ -5032,8 +5032,7 @@ static PyThread_type_lock *_ssl_locks = NULL;
 static void
 _ssl_threadid_callback(CRYPTO_THREADID *id)
 {
-    CRYPTO_THREADID_set_numeric(id,
-                                (unsigned long)PyThread_get_thread_ident());
+    CRYPTO_THREADID_set_numeric(id, PyThread_get_thread_ident());
 }
 #else
 /* deprecated CRYPTO_set_id_callback() API. */

Modules/_threadmodule.c

@@ -267,7 +267,7 @@ static PyTypeObject Locktype = {
 typedef struct {
     PyObject_HEAD
     PyThread_type_lock rlock_lock;
-    long rlock_owner;
+    unsigned long rlock_owner;
     unsigned long rlock_count;
     PyObject *in_weakreflist;
 } rlockobject;
@@ -293,7 +293,7 @@ static PyObject *
 rlock_acquire(rlockobject *self, PyObject *args, PyObject *kwds)
 {
     _PyTime_t timeout;
-    long tid;
+    unsigned long tid;
     PyLockStatus r = PY_LOCK_ACQUIRED;
 
     if (lock_acquire_parse_args(args, kwds, &timeout) < 0)
@@ -342,7 +342,7 @@ the lock is taken and its internal counter initialized to 1.");
 static PyObject *
 rlock_release(rlockobject *self)
 {
-    long tid = PyThread_get_thread_ident();
+    unsigned long tid = PyThread_get_thread_ident();
 
     if (self->rlock_count == 0 || self->rlock_owner != tid) {
         PyErr_SetString(PyExc_RuntimeError,
@@ -371,11 +371,11 @@ to be available for other threads.");
 static PyObject *
 rlock_acquire_restore(rlockobject *self, PyObject *args)
 {
-    long owner;
+    unsigned long owner;
     unsigned long count;
     int r = 1;
 
-    if (!PyArg_ParseTuple(args, "(kl):_acquire_restore", &count, &owner))
+    if (!PyArg_ParseTuple(args, "(kk):_acquire_restore", &count, &owner))
         return NULL;
 
     if (!PyThread_acquire_lock(self->rlock_lock, 0)) {
@@ -401,7 +401,7 @@ For internal use by `threading.Condition`.");
 static PyObject *
 rlock_release_save(rlockobject *self)
 {
-    long owner;
+    unsigned long owner;
     unsigned long count;
 
     if (self->rlock_count == 0) {
@@ -415,7 +415,7 @@ rlock_release_save(rlockobject *self)
     self->rlock_count = 0;
     self->rlock_owner = 0;
     PyThread_release_lock(self->rlock_lock);
-    return Py_BuildValue("kl", count, owner);
+    return Py_BuildValue("kk", count, owner);
 }
 
 PyDoc_STRVAR(rlock_release_save_doc,
@@ -427,7 +427,7 @@ For internal use by `threading.Condition`.");
 static PyObject *
 rlock_is_owned(rlockobject *self)
 {
-    long tid = PyThread_get_thread_ident();
+    unsigned long tid = PyThread_get_thread_ident();
 
     if (self->rlock_count > 0 && self->rlock_owner == tid) {
         Py_RETURN_TRUE;
@@ -1031,7 +1031,7 @@ thread_PyThread_start_new_thread(PyObject *self, PyObject *fargs)
 {
     PyObject *func, *args, *keyw = NULL;
     struct bootstate *boot;
-    long ident;
+    unsigned long ident;
 
     if (!PyArg_UnpackTuple(fargs, "start_new_thread", 2, 3,
                            &func, &args, &keyw))
@@ -1068,7 +1068,7 @@ thread_PyThread_start_new_thread(PyObject *self, PyObject *fargs)
     Py_XINCREF(keyw);
     PyEval_InitThreads(); /* Start the interpreter's thread-awareness */
     ident = PyThread_start_new_thread(t_bootstrap, (void*) boot);
-    if (ident == -1) {
+    if (ident == PYTHREAD_INVALID_THREAD_ID) {
         PyErr_SetString(ThreadError, "can't start new thread");
         Py_DECREF(func);
         Py_DECREF(args);
@@ -1077,7 +1077,7 @@ thread_PyThread_start_new_thread(PyObject *self, PyObject *fargs)
         PyMem_DEL(boot);
         return NULL;
     }
-    return PyLong_FromLong(ident);
+    return PyLong_FromUnsignedLong(ident);
 }
 
 PyDoc_STRVAR(start_new_doc,
@@ -1137,13 +1137,12 @@ information about locks.");
 static PyObject *
 thread_get_ident(PyObject *self)
 {
-    long ident;
-    ident = PyThread_get_thread_ident();
-    if (ident == -1) {
+    unsigned long ident = PyThread_get_thread_ident();
+    if (ident == PYTHREAD_INVALID_THREAD_ID) {
         PyErr_SetString(ThreadError, "no current thread ident");
         return NULL;
     }
-    return PyLong_FromLong(ident);
+    return PyLong_FromUnsignedLong(ident);
 }
 
 PyDoc_STRVAR(get_ident_doc,

Modules/clinic/signalmodule.c.h

@@ -395,16 +395,17 @@ PyDoc_STRVAR(signal_pthread_kill__doc__,
     {"pthread_kill", (PyCFunction)signal_pthread_kill, METH_FASTCALL, signal_pthread_kill__doc__},
 
 static PyObject *
-signal_pthread_kill_impl(PyObject *module, long thread_id, int signalnum);
+signal_pthread_kill_impl(PyObject *module, unsigned long thread_id,
+                         int signalnum);
 
 static PyObject *
 signal_pthread_kill(PyObject *module, PyObject **args, Py_ssize_t nargs, PyObject *kwnames)
 {
     PyObject *return_value = NULL;
-    long thread_id;
+    unsigned long thread_id;
     int signalnum;
 
-    if (!_PyArg_ParseStack(args, nargs, "li:pthread_kill",
+    if (!_PyArg_ParseStack(args, nargs, "ki:pthread_kill",
         &thread_id, &signalnum)) {
         goto exit;
     }
@@ -463,4 +464,4 @@ signal_pthread_kill(PyObject *module, PyObject **args, Py_ssize_t nargs, PyObjec
 #ifndef SIGNAL_PTHREAD_KILL_METHODDEF
     #define SIGNAL_PTHREAD_KILL_METHODDEF
 #endif /* !defined(SIGNAL_PTHREAD_KILL_METHODDEF) */
-/*[clinic end generated code: output=fab3dba32c058588 input=a9049054013a1b77]*/
+/*[clinic end generated code: output=c1a3f374b2c77e5d input=a9049054013a1b77]*/

Modules/faulthandler.c

@@ -678,7 +678,7 @@ faulthandler_dump_traceback_later(PyObject *self,
     /* Arm these locks to serve as events when released */
     PyThread_acquire_lock(thread.running, 1);
 
-    if (PyThread_start_new_thread(faulthandler_thread, NULL) == -1) {
+    if (PyThread_start_new_thread(faulthandler_thread, NULL) == PYTHREAD_INVALID_THREAD_ID) {
         PyThread_release_lock(thread.running);
         Py_CLEAR(thread.file);
         PyMem_Free(header);

Modules/signalmodule.c

@@ -88,7 +88,7 @@ module signal
 #ifdef WITH_THREAD
 #include <sys/types.h> /* For pid_t */
 #include "pythread.h"
-static long main_thread;
+static unsigned long main_thread;
 static pid_t main_pid;
 #endif
 
@@ -1088,16 +1088,17 @@ signal_sigtimedwait_impl(PyObject *module, PyObject *sigset,
 /*[clinic input]
 signal.pthread_kill
 
-    thread_id:  long
+    thread_id:  unsigned_long(bitwise=True)
     signalnum:  int
     /
 
 Send a signal to a thread.
 [clinic start generated code]*/
 
 static PyObject *
-signal_pthread_kill_impl(PyObject *module, long thread_id, int signalnum)
-/*[clinic end generated code: output=2a09ce41f1c4228a input=77ed6a3b6f2a8122]*/
+signal_pthread_kill_impl(PyObject *module, unsigned long thread_id,
+                         int signalnum)
+/*[clinic end generated code: output=7629919b791bc27f input=1d901f2c7bb544ff]*/
 {
     int err;
 

Python/ceval.c

@@ -148,7 +148,7 @@ static long dxp[256];
 #include "pythread.h"
 
 static PyThread_type_lock pending_lock = 0; /* for pending calls */
-static long main_thread = 0;
+static unsigned long main_thread = 0;
 /* This single variable consolidates all requests to break out of the fast path
    in the eval loop. */
 static _Py_atomic_int eval_breaker = {0};