diff -r 10cf594ace4b Lib/trace.py
--- a/Lib/trace.py	Sun Jun 29 17:44:05 2014 -0400
+++ b/Lib/trace.py	Sun Jun 29 20:58:21 2014 -0400
@@ -58,6 +58,7 @@
 import gc
 import dis
 import pickle
+import io
 from warnings import warn as _warn
 try:
     from time import monotonic as _time
@@ -327,10 +328,13 @@
             else:
                 lnotab = {}
             if lnotab:
-                source = linecache.getlines(filename)
+                source = linecache.getlines(filename, sys.modules[modulename].__dict__)
                 coverpath = os.path.join(dir, modulename + ".cover")
-                with open(filename, 'rb') as fp:
-                    encoding, _ = tokenize.detect_encoding(fp.readline)
+                try:
+                    with open(filename, 'rb') as fp:
+                        encoding, _ = tokenize.detect_encoding(fp.readline)
+                except IOError:
+                    encoding = None
                 n_hits, n_lines = self.write_results_file(coverpath, source,
                                                           lnotab, count, encoding)
                 if summary and n_lines:
@@ -416,34 +420,45 @@
     line that contains only a string or a part of a triple-quoted
     string.
     """
+    with open(filename, encoding=encoding) as f:
+        return _find_strings_stream(f)
+
+def _find_strings_stream(stream):
     d = {}
     # If the first token is a string, then it's the module docstring.
     # Add this special case so that the test in the loop passes.
     prev_ttype = token.INDENT
-    with open(filename, encoding=encoding) as f:
-        tok = tokenize.generate_tokens(f.readline)
-        for ttype, tstr, start, end, line in tok:
-            if ttype == token.STRING:
-                if prev_ttype == token.INDENT:
-                    sline, scol = start
-                    eline, ecol = end
-                    for i in range(sline, eline + 1):
-                        d[i] = 1
-            prev_ttype = ttype
+    tok = tokenize.generate_tokens(stream.readline)
+    for ttype, tstr, start, end, line in tok:
+        if ttype == token.STRING:
+            if prev_ttype == token.INDENT:
+                sline, scol = start
+                eline, ecol = end
+                for i in range(sline, eline + 1):
+                    d[i] = 1
+        prev_ttype = ttype
     return d
 
 def _find_executable_linenos(filename):
     """Return dict where keys are line numbers in the line number table."""
-    try:
-        with tokenize.open(filename) as f:
-            prog = f.read()
-            encoding = f.encoding
-    except OSError as err:
-        print(("Not printing coverage data for %r: %s"
-                              % (filename, err)), file=sys.stderr)
-        return {}
-    code = compile(prog, filename, "exec")
-    strs = _find_strings(filename, encoding)
+    modulename = fullmodname(filename)
+    module = sys.modules[modulename]
+    loader = getattr(module, '__loader__', None)
+    if loader:
+        code = loader.get_code(modulename)
+        source = loader.get_source(modulename)
+        strs = _find_strings_stream(io.StringIO(source))
+    else:
+        try:
+            with tokenize.open(filename) as f:
+                prog = f.read()
+                encoding = f.encoding
+        except OSError as err:
+            print(("Not printing coverage data for %r: %s"
+                                  % (filename, err)), file=sys.stderr)
+            return {}
+        code = compile(prog, filename, "exec")
+        strs = _find_strings(filename, encoding)
     return _find_lines(code, strs)
 
 class Trace: