Use python3.7's opcode tracing if possible

pythonfuzz/tracer.py

@@ -5,7 +5,32 @@
 prev_filename = ''
 data = collections.defaultdict(set)
 
-def trace(frame, event, arg):
+def trace_opcode(frame, event, arg):
+    if event != 'opcode':
+        return trace
+
+    global prev_line
+    global prev_filename
+
+    func_filename = frame.f_code.co_filename
+    func_line_no = frame.f_lineno
+    func_opcode = frame.f_code
+
+    if func_filename != prev_filename:
+        # We need a way to keep track of inter-files transferts,
+        # and since we don't really care about the details of the coverage,
+        # concatenating the two filenames in enough.
+        data[func_filename + prev_filename].add((prev_line, func_line_no, func_opcode))
+    else:
+        data[func_filename].add((prev_line, func_line_no, func_opcode))
+
+    prev_line = func_line_no
+    prev_filename = func_filename
+
+    return trace
+
+
+def trace_default(frame, event, arg):
     if event != 'line':
         return trace
 
@@ -29,5 +54,9 @@ def trace(frame, event, arg):
     return trace
 
 
+trace = trace_default
+if sys.version_info >= (3, 7):
+    trace = trace_opcode
+
 def get_coverage():
     return sum(map(len, data.values()))