Create a stub class and singleton to represent main

This is an updated patch from pull request #16 which will throw an
exception if coro is called without starting the event_loop(). The
main update is to bring it up to date with recent changes and make
the linux poller throw the correct exception in this case.

coro/_coro.pyx

@@ -152,6 +152,10 @@ include "fifo.pyx"
 
 import sys
 
+class YieldFromMain (Exception):
+    "attempt to yield from main"
+    pass
+
 class ScheduleError (Exception):
     "attempt to schedule an already-scheduled coroutine"
     pass
@@ -192,7 +196,8 @@ cdef extern int SHRAP_STACK_PAD
 # forward
 #cdef public class sched  [ object sched_object, type sched_type ]
 cdef public class queue_poller [ object queue_poller_object, type queue_poller_type ]
-cdef sched the_scheduler "the_scheduler"
+cdef sched the_scheduler "_the_scheduler"
+cdef main_stub the_main_coro "the_main_coro"
 cdef queue_poller the_poller "the_poller"
 
 cdef int default_selfishness
@@ -318,7 +323,7 @@ cdef public class coro [ object _coro_object, type _coro_type ]:
         # save exception data
         self.save_exception_data()
         if not self.dead:
-            the_scheduler._current = None
+            the_scheduler._current = the_main_coro
             the_scheduler._last = self
         else:
             # Beware.  When this coroutine is 'dead', it's about to __swap()
@@ -684,6 +689,17 @@ cdef public class coro [ object _coro_object, type _coro_type ]:
 
         self.waiting_joiners.wait()
 
+cdef class main_stub (coro):
+    """This class serves only one purpose - to catch attempts at yielding() from main,
+    which almost certainly means someone forgot to run inside the event loop."""
+
+    def __init__ (self):
+        self.name = b'main/scheduler'
+        self.id = -1
+
+    cdef __yield (self):
+        raise YieldFromMain ("is the event loop running?")
+
 def get_live_coros():
     """Get the number of live coroutines.
 
@@ -878,7 +894,6 @@ ELSE:
 # ================================================================================
 
 cdef public class sched [ object sched_object, type sched_type ]:
-
     def __init__ (self, stack_size=4*1024*1024):
         self.stack_size = stack_size
         # tried using mmap & MAP_STACK, always got ENOMEM
@@ -889,7 +904,7 @@ cdef public class sched [ object sched_object, type sched_type ]:
         #    <int>self.stack_base,
         #    <int>self.stack_base + stack_size
         #    ))
-        self._current = None
+        self._current = the_main_coro
         self._last = None
         self.pending = []
         self.staging = []
@@ -1082,9 +1097,6 @@ cdef public class sched [ object sched_object, type sched_type ]:
         """
         cdef timebomb tb
         cdef event e
-        IF CORO_DEBUG:
-            # can't call with_timeout() from main...
-            assert self._current is not None
 
         # Negative timeout is treated the same as 0.
         if delta < 0:
@@ -1328,6 +1340,8 @@ IF COMPILE_LIO:
 # python.  'global' doesn't do the trick.  However, defining global
 # functions to access them works...
 
+# singletons
+the_main_coro = main_stub()
 the_scheduler = sched()
 the_poller = queue_poller()
 _the_scheduler = the_scheduler
@@ -1341,15 +1355,8 @@ def print_stderr (s):
     :param s: A string to print.
     """
     try:
-        current_thread = current()
-        if current_thread is None:
-            thread_id = -1
-        else:
-            thread_id = current().thread_id()
-        output = '%i:\t%s %s' % (
-                    thread_id,
-                    tsc_time_module.now_tsc().ctime(),
-                    s)
+        timestamp = tsc_time_module.now_tsc().ctime()
+        output = '%i:\t%s %s' % (current().thread_id(), timestamp, s)
         saved_stderr.write(output)
         if not output.endswith('\n'):
             saved_stderr.write('\n')
@@ -1433,9 +1440,8 @@ cdef void info(int sig):
 
     co = the_scheduler._current
     frame = _PyThreadState_Current.frame
-    if co:
-        stdio.fprintf (
-            stdio.stderr, 'coro %i "%s" at %s: %s %i\n',
+    if co is not the_main_coro:
+        stdio.fprintf(stdio.stderr, 'coro %i "%s" at %s: %s %i\n',
             co.id,
             co.name,
             <bytes>frame.f_code.co_filename,

coro/linux_poller.pyx

@@ -305,6 +305,10 @@ cdef public class queue_poller [ object queue_poller_object, type queue_poller_t
     cdef _register_event(self, event_key ek, unsigned int flags): 
         cdef int r
         cdef epoll_event org_e
+
+        if self.ep_fd == -1:
+            raise YieldFromMain("is the event loop running?")
+
         org_e.data.fd = ek.fd
         org_e.events = ek.events | flags 
 

coro/local.pyx

@@ -20,8 +20,6 @@
 
 # $Header: //prod/main/ap/shrapnel/coro/local.pyx#3 $
 
-cdef object __dummy_main
-__dummy_main = {}
 
 cdef class ThreadLocal:
 
@@ -95,13 +93,9 @@ cdef class ThreadLocal:
         cdef coro co
 
         co = the_scheduler._current
-        if co is None:
-            # Really shouldn't use these until coro is started.
-            _tdict = __dummy_main
-        else:
-            if co._tdict is None:
-                co._tdict = {}
-            _tdict = co._tdict
+        if co._tdict is None:
+            co._tdict = {}
+        _tdict = co._tdict
         ldict = PyDict_GET_ITEM_SAFE(_tdict, self.key, None)
         if ldict is None:
             ldict = {}

test/runner

@@ -8,12 +8,14 @@ python test_isemaphore.py
 python test_lio.py
 python test_local.py
 python test_lru.py
+python test_main.py
 python test_mutex.py
 #python test_notify_of_close.py
 python test_poller.py
 python test_profile.py
 python test_read_stream.py
 #python test_readv.py
+python test_reenter.py
 python test_rw_lock.py
 python test_semaphore.py
 python test_socket.py

test/test_main.py

@@ -0,0 +1,16 @@
+import coro
+import unittest
+
+class CoroMain(unittest.TestCase):
+    def test_coro_main_connect(self):
+        s = coro.tcp_sock()
+        with self.assertRaises(coro.YieldFromMain):
+            s.connect (('127.0.0.1', 80))
+
+    def test_coro_main_yield(self):
+        s = coro.tcp_sock()
+        with self.assertRaises(coro.YieldFromMain):
+            coro.yield_slice()
+
+if __name__ == '__main__':
+    unittest.main()

test/test_reenter.py

@@ -0,0 +1,21 @@
+import coro
+import unittest
+
+def exit_coro():
+    coro.sleep_relative(0.1)
+    coro.set_exit()
+
+
+class CoroMain(unittest.TestCase):
+    def test_coro_main(self):
+        coro.set_print_exit_string(None)
+
+        for x in range(4):
+            try:
+                coro.spawn(exit_coro)
+                coro.event_loop()
+            except SystemExit:
+                pass
+
+if __name__ == '__main__':
+    unittest.main()