From: Miss Islington (bot) <31488909+miss-islington@users.noreply.github.com>
Date: Thu, 5 Mar 2020 01:04:38 +0000 (-0800)
Subject: bpo-13487: Use sys.modules.copy() in inspect.getmodule() for thread safety. (GH-18786)
X-Git-Tag: v3.8.3rc1~134
X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=6b452ff97f70eca79ab956987cc04b6586feca00;p=thirdparty%2FPython%2Fcpython.git

bpo-13487: Use sys.modules.copy() in inspect.getmodule() for thread safety. (GH-18786)


`list(sys.modules.items())` was apparently not immune to "dictionary
changed size during iteration" errors.

Tested internally using an integration test that has run into this a couple of times in the past two years.  With this patch applied, the test is no longer flaky.
(cherry picked from commit 85cf1d514b84dc9a4bcb40e20a12e1d82ff19f20)

Co-authored-by: Gregory P. Smith <gps@google.com>
---

diff --git a/Lib/inspect.py b/Lib/inspect.py
index 3ff395ca3337..e8ea8c221f82 100644
--- a/Lib/inspect.py
+++ b/Lib/inspect.py
@@ -741,7 +741,7 @@ def getmodule(object, _filename=None):
         return sys.modules.get(modulesbyfile[file])
     # Update the filename to module name cache and check yet again
     # Copy sys.modules in order to cope with changes while iterating
-    for modname, module in list(sys.modules.items()):
+    for modname, module in sys.modules.copy().items():
         if ismodule(module) and hasattr(module, '__file__'):
             f = module.__file__
             if f == _filesbymodname.get(modname, None):
diff --git a/Misc/NEWS.d/next/Library/2020-03-04-16-10-59.bpo-13487.gqe4Fb.rst b/Misc/NEWS.d/next/Library/2020-03-04-16-10-59.bpo-13487.gqe4Fb.rst
new file mode 100644
index 000000000000..5a1f02a7bdf3
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2020-03-04-16-10-59.bpo-13487.gqe4Fb.rst
@@ -0,0 +1,3 @@
+Avoid a possible *"RuntimeError: dictionary changed size during iteration"*
+from :func:`inspect.getmodule` when it tried to loop through
+:attr:`sys.modules`.