Correctly free DTrace resources.

kwitaszczyk · kwitaszczyk · commit 0a889ceed8cb · 2022-02-09T14:36:55.000Z
Cython's cdef attributes are not regular class attributes as in Python.
hasattr(object, name) always returns False for a cdef attribute
corresponding to name.

Instead, we should simply check a pointer's value. I couldn't confirm
it in any documentation but, based on examples I found and my
experiments, it seems that a cdef pointer is always initially set to
NULL, at least when declared as a class attribute.
diff --git a/dtrace_cython/consumer.pyx b/dtrace_cython/consumer.pyx
@@ -312,7 +312,7 @@ cdef class DTraceConsumer:
         self.walk_func = noop_walk if walk_func is None else walk_func
 
         cdef int err
-        if not hasattr(self, 'handle'):
+        if self.handle == NULL:
             # ensure we only grab 1 - cython might call init twice, of more.
             self.handle = dtrace_open(3, 0, &err)
         if self.handle == NULL:
@@ -331,8 +331,9 @@ cdef class DTraceConsumer:
         """
         Release DTrace handle.
         """
-        if hasattr(self, 'handle') and self.handle != NULL:
+        if self.handle != NULL:
             dtrace_close(self.handle)
+            self.handle = NULL
 
     cpdef compile(self, str script):
         """
@@ -437,7 +438,7 @@ cdef class DTraceContinuousConsumer:
         self.script = script.encode("utf-8")
 
         cdef int err
-        if not hasattr(self, 'handle'):
+        if self.handle == NULL:
             # ensure we only grab 1 - cython might call init twice, of more.
             self.handle = dtrace_open(3, 0, &err)
         if self.handle == NULL:
@@ -456,9 +457,10 @@ cdef class DTraceContinuousConsumer:
         """
         Release DTrace handle.
         """
-        if hasattr(self, 'handle') and self.handle != NULL:
+        if self.handle != NULL:
             dtrace_stop(self.handle)
             dtrace_close(self.handle)
+            self.handle = NULL
 
     cpdef go(self):
         """
