closes bpo-31650: PEP 552 (Deterministic pycs) implementation (#4575)
Python now supports checking bytecode cache up-to-dateness with a hash of the
source contents rather than volatile source metadata. See the PEP for details.
While a fairly straightforward idea, quite a lot of code had to be modified due
to the pervasiveness of pyc implementation details in the codebase. Changes in
this commit include:
- The core changes to importlib to understand how to read, validate, and
regenerate hash-based pycs.
- Support for generating hash-based pycs in py_compile and compileall.
- Modifications to our siphash implementation to support passing a custom
key. We then expose it to importlib through _imp.
- Updates to all places in the interpreter, standard library, and tests that
manually generate or parse pyc files to grok the new format.
- Support in the interpreter command line code for long options like
--check-hash-based-pycs.
- Tests and documentation for all of the above.
diff --git a/Python/pythonrun.c b/Python/pythonrun.c
index b528575..26f74c8 100644
--- a/Python/pythonrun.c
+++ b/Python/pythonrun.c
@@ -1053,7 +1053,8 @@
"Bad magic number in .pyc file");
return NULL;
}
- /* Skip mtime and size */
+ /* Skip the rest of the header. */
+ (void) PyMarshal_ReadLongFromFile(fp);
(void) PyMarshal_ReadLongFromFile(fp);
(void) PyMarshal_ReadLongFromFile(fp);
if (PyErr_Occurred())