bpo-31370: Remove support for threads-less builds (python#3385)

* Remove Setup.config
* Always define WITH_THREAD for compatibility.

Doc/whatsnew/3.7.rst

@@ -344,6 +344,9 @@ Build and C API Changes
   download a copy of 32-bit Python for this purpose.  (Contributed by Zachary
   Ware in :issue:`30450`.)
 
+* Support for building ``--without-threads`` is removed.
+  (Contributed by Antoine Pitrou in :issue:`31370`.).
+
 
 Deprecated
 ==========

Include/Python.h

@@ -18,7 +18,7 @@
 #error "Python's source code assumes C's unsigned char is an 8-bit type."
 #endif
 
-#if defined(__sgi) && defined(WITH_THREAD) && !defined(_SGI_MP_SOURCE)
+#if defined(__sgi) && !defined(_SGI_MP_SOURCE)
 #define _SGI_MP_SOURCE
 #endif
 

Include/ceval.h

@@ -183,8 +183,6 @@ PyAPI_FUNC(PyObject *) _PyEval_EvalFrameDefault(struct _frame *f, int exc);
 PyAPI_FUNC(PyThreadState *) PyEval_SaveThread(void);
 PyAPI_FUNC(void) PyEval_RestoreThread(PyThreadState *);
 
-#ifdef WITH_THREAD
-
 PyAPI_FUNC(int)  PyEval_ThreadsInitialized(void);
 PyAPI_FUNC(void) PyEval_InitThreads(void);
 #ifndef Py_LIMITED_API
@@ -213,15 +211,6 @@ PyAPI_FUNC(Py_ssize_t) _PyEval_RequestCodeExtraIndex(freefunc);
 #define Py_END_ALLOW_THREADS    PyEval_RestoreThread(_save); \
                  }
 
-#else /* !WITH_THREAD */
-
-#define Py_BEGIN_ALLOW_THREADS {
-#define Py_BLOCK_THREADS
-#define Py_UNBLOCK_THREADS
-#define Py_END_ALLOW_THREADS }
-
-#endif /* !WITH_THREAD */
-
 #ifndef Py_LIMITED_API
 PyAPI_FUNC(int) _PyEval_SliceIndex(PyObject *, Py_ssize_t *);
 PyAPI_FUNC(int) _PyEval_SliceIndexNotNone(PyObject *, Py_ssize_t *);

Include/import.h

@@ -100,13 +100,8 @@ PyAPI_FUNC(int) PyImport_ImportFrozenModule(
     );
 
 #ifndef Py_LIMITED_API
-#ifdef WITH_THREAD
 PyAPI_FUNC(void) _PyImport_AcquireLock(void);
 PyAPI_FUNC(int) _PyImport_ReleaseLock(void);
-#else
-#define _PyImport_AcquireLock()
-#define _PyImport_ReleaseLock() 1
-#endif
 
 PyAPI_FUNC(void) _PyImport_ReInitLock(void);
 

Include/pyport.h

@@ -797,4 +797,12 @@ extern _invalid_parameter_handler _Py_silent_invalid_parameter_handler;
 #include <android/api-level.h>
 #endif
 
+/* This macro used to tell whether Python was built with multithreading
+ * enabled.  Now multithreading is always enabled, but keep the macro
+ * for compatibility.
+ */
+#ifndef WITH_THREAD
+#define WITH_THREAD
+#endif
+
 #endif /* Py_PYPORT_H */

Include/pystate.h

@@ -218,12 +218,10 @@ PyAPI_FUNC(void) PyThreadState_Delete(PyThreadState *);
 #ifndef Py_LIMITED_API
 PyAPI_FUNC(void) _PyThreadState_DeleteExcept(PyThreadState *tstate);
 #endif /* !Py_LIMITED_API */
-#ifdef WITH_THREAD
 PyAPI_FUNC(void) PyThreadState_DeleteCurrent(void);
 #ifndef Py_LIMITED_API
 PyAPI_FUNC(void) _PyGILState_Reinit(void);
 #endif /* !Py_LIMITED_API */
-#endif
 
 /* Return the current thread state. The global interpreter lock must be held.
  * When the current thread state is NULL, this issues a fatal error (so that
@@ -257,7 +255,6 @@ typedef
     enum {PyGILState_LOCKED, PyGILState_UNLOCKED}
         PyGILState_STATE;
 
-#ifdef WITH_THREAD
 
 /* Ensure that the current thread is ready to call the Python
    C API, regardless of the current state of Python, or of its
@@ -319,7 +316,6 @@ PyAPI_FUNC(int) PyGILState_Check(void);
 PyAPI_FUNC(PyInterpreterState *) _PyGILState_GetInterpreterStateUnsafe(void);
 #endif
 
-#endif   /* #ifdef WITH_THREAD */
 
 /* The implementation of sys._current_frames()  Returns a dict mapping
    thread id to that thread's current frame.

Lib/_pydecimal.py

@@ -436,75 +436,34 @@ class FloatOperation(DecimalException, TypeError):
 # work for older Pythons.  If threads are not part of the build, create a
 # mock threading object with threading.local() returning the module namespace.
 
-try:
-    import threading
-except ImportError:
-    # Python was compiled without threads; create a mock object instead
-    class MockThreading(object):
-        def local(self, sys=sys):
-            return sys.modules[__xname__]
-    threading = MockThreading()
-    del MockThreading
-
-try:
-    threading.local
-
-except AttributeError:
-
-    # To fix reloading, force it to create a new context
-    # Old contexts have different exceptions in their dicts, making problems.
-    if hasattr(threading.current_thread(), '__decimal_context__'):
-        del threading.current_thread().__decimal_context__
-
-    def setcontext(context):
-        """Set this thread's context to context."""
-        if context in (DefaultContext, BasicContext, ExtendedContext):
-            context = context.copy()
-            context.clear_flags()
-        threading.current_thread().__decimal_context__ = context
-
-    def getcontext():
-        """Returns this thread's context.
-
-        If this thread does not yet have a context, returns
-        a new context and sets this thread's context.
-        New contexts are copies of DefaultContext.
-        """
-        try:
-            return threading.current_thread().__decimal_context__
-        except AttributeError:
-            context = Context()
-            threading.current_thread().__decimal_context__ = context
-            return context
+import threading
 
-else:
+local = threading.local()
+if hasattr(local, '__decimal_context__'):
+    del local.__decimal_context__
 
-    local = threading.local()
-    if hasattr(local, '__decimal_context__'):
-        del local.__decimal_context__
+def getcontext(_local=local):
+    """Returns this thread's context.
 
-    def getcontext(_local=local):
-        """Returns this thread's context.
-
-        If this thread does not yet have a context, returns
-        a new context and sets this thread's context.
-        New contexts are copies of DefaultContext.
-        """
-        try:
-            return _local.__decimal_context__
-        except AttributeError:
-            context = Context()
-            _local.__decimal_context__ = context
-            return context
-
-    def setcontext(context, _local=local):
-        """Set this thread's context to context."""
-        if context in (DefaultContext, BasicContext, ExtendedContext):
-            context = context.copy()
-            context.clear_flags()
+    If this thread does not yet have a context, returns
+    a new context and sets this thread's context.
+    New contexts are copies of DefaultContext.
+    """
+    try:
+        return _local.__decimal_context__
+    except AttributeError:
+        context = Context()
         _local.__decimal_context__ = context
+        return context
+
+def setcontext(context, _local=local):
+    """Set this thread's context to context."""
+    if context in (DefaultContext, BasicContext, ExtendedContext):
+        context = context.copy()
+        context.clear_flags()
+    _local.__decimal_context__ = context
 
-    del threading, local        # Don't contaminate the namespace
+del threading, local        # Don't contaminate the namespace
 
 def localcontext(ctx=None):
     """Return a context manager for a copy of the supplied context

Lib/_pyio.py

@@ -9,10 +9,7 @@
 import stat
 import sys
 # Import _thread instead of threading to reduce startup cost
-try:
-    from _thread import allocate_lock as Lock
-except ImportError:
-    from _dummy_thread import allocate_lock as Lock
+from _thread import allocate_lock as Lock
 if sys.platform in {'win32', 'cygwin'}:
     from msvcrt import setmode as _setmode
 else:

Lib/_strptime.py

@@ -19,10 +19,7 @@
 from datetime import (date as datetime_date,
                       timedelta as datetime_timedelta,
                       timezone as datetime_timezone)
-try:
-    from _thread import allocate_lock as _thread_allocate_lock
-except ImportError:
-    from _dummy_thread import allocate_lock as _thread_allocate_lock
+from _thread import allocate_lock as _thread_allocate_lock
 
 __all__ = []
 

Lib/bz2.py

@@ -14,11 +14,7 @@
 import os
 import warnings
 import _compression
-
-try:
-    from threading import RLock
-except ImportError:
-    from dummy_threading import RLock
+from threading import RLock
 
 from _bz2 import BZ2Compressor, BZ2Decompressor