From 392d901aba3930243c516ee2a9ef00a090357ac6 Mon Sep 17 00:00:00 2001
From: Ned Batchelder <ned@nedbatchelder.com>
Date: Wed, 10 Jan 2018 21:47:09 -0500
Subject: Python 3.7 tweaked the layout of .pyc files

---
 coverage/execfile.py | 19 ++++++++++++++-----
 lab/show_pyc.py      | 25 ++++++++++++++++++-------
 2 files changed, 32 insertions(+), 12 deletions(-)

diff --git a/coverage/execfile.py b/coverage/execfile.py
index 693f54f..ffe3ca1 100644
--- a/coverage/execfile.py
+++ b/coverage/execfile.py
@@ -5,6 +5,7 @@
 
 import marshal
 import os
+import struct
 import sys
 import types
 
@@ -253,11 +254,19 @@ def make_code_from_pyc(filename):
         if magic != PYC_MAGIC_NUMBER:
             raise NoCode("Bad magic number in .pyc file")
 
-        # Skip the junk in the header that we don't need.
-        fpyc.read(4)            # Skip the moddate.
-        if sys.version_info >= (3, 3):
-            # 3.3 added another long to the header (size), skip it.
-            fpyc.read(4)
+        date_based = True
+        if sys.version_info >= (3, 7):
+            flags = struct.unpack('<L', fpyc.read(4))[0]
+            hash_based = flags & 0x01
+            if hash_based:
+                fpyc.read(8)    # Skip the hash.
+                date_based = False
+        if date_based:
+            # Skip the junk in the header that we don't need.
+            fpyc.read(4)            # Skip the moddate.
+            if sys.version_info >= (3, 3):
+                # 3.3 added another long to the header (size), skip it.
+                fpyc.read(4)
 
         # The rest of the file is the code object we want.
         code = marshal.load(fpyc)
diff --git a/lab/show_pyc.py b/lab/show_pyc.py
index 0a28e4f..525797a 100644
--- a/lab/show_pyc.py
+++ b/lab/show_pyc.py
@@ -13,14 +13,25 @@ import types
 def show_pyc_file(fname):
     f = open(fname, "rb")
     magic = f.read(4)
-    moddate = f.read(4)
-    modtime = time.asctime(time.localtime(struct.unpack('<L', moddate)[0]))
     print("magic %s" % (binascii.hexlify(magic)))
-    print("moddate %s (%s)" % (binascii.hexlify(moddate), modtime))
-    if sys.version_info >= (3, 3):
-        # 3.3 added another long to the header (size).
-        size = f.read(4)
-        print("pysize %s (%d)" % (binascii.hexlify(size), struct.unpack('<L', size)[0]))
+    read_date_and_size = True
+    if sys.version_info >= (3, 7):
+        # 3.7 added a flags word
+        flags = struct.unpack('<L', f.read(4))[0]
+        hash_based = flags & 0x01
+        check_source = flags & 0x02
+        print("flags 0x%08x" % (flags,))
+        if hash_based:
+            source_hash = f.read(8)
+            read_date_and_size = False
+    if read_date_and_size:
+        moddate = f.read(4)
+        modtime = time.asctime(time.localtime(struct.unpack('<L', moddate)[0]))
+        print("moddate %s (%s)" % (binascii.hexlify(moddate), modtime))
+        if sys.version_info >= (3, 3):
+            # 3.3 added another long to the header (size).
+            size = f.read(4)
+            print("pysize %s (%d)" % (binascii.hexlify(size), struct.unpack('<L', size)[0]))
     code = marshal.load(f)
     show_code(code)
 
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