Possible fix for #445 and #420

The line that seems to break #445 is the import of weakref, even if we never
use it.  Delaying the import until we need it seems to fix #445.

1 files changed, 16 insertions, 13 deletions

diff --git a/coverage/ctracer/tracer.c b/coverage/ctracer/tracer.c
index dba8a11c..25036f99 100644
--- a/coverage/ctracer/tracer.c
+++ b/coverage/ctracer/tracer.c
@@ -64,24 +64,11 @@ static int
 CTracer_init(CTracer *self, PyObject *args_unused, PyObject *kwds_unused)
 {
     int ret = RET_ERROR;
-    PyObject * weakref = NULL;
 
     if (DataStack_init(&self->stats, &self->data_stack) < 0) {
         goto error;
     }
 
-    weakref = PyImport_ImportModule("weakref");
-    if (weakref == NULL) {
-        goto error;
-    }
-    STATS( self->stats.pycalls++; )
-    self->data_stack_index = PyObject_CallMethod(weakref, "WeakKeyDictionary", NULL);
-    Py_XDECREF(weakref);
-
-    if (self->data_stack_index == NULL) {
-        goto error;
-    }
-
     self->pdata_stack = &self->data_stack;
 
     self->cur_entry.last_line = -1;
@@ -212,6 +199,22 @@ CTracer_set_pdata_stack(CTracer *self)
     if (self->concur_id_func != Py_None) {
         int the_index = 0;
 
+        if (self->data_stack_index == NULL) {
+            PyObject * weakref = NULL;
+
+            weakref = PyImport_ImportModule("weakref");
+            if (weakref == NULL) {
+                goto error;
+            }
+            STATS( self->stats.pycalls++; )
+            self->data_stack_index = PyObject_CallMethod(weakref, "WeakKeyDictionary", NULL);
+            Py_XDECREF(weakref);
+
+            if (self->data_stack_index == NULL) {
+                goto error;
+            }
+        }
+
         STATS( self->stats.pycalls++; )
         co_obj = PyObject_CallObject(self->concur_id_func, NULL);
         if (co_obj == NULL) {