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author | Michał Górny <mgorny@gentoo.org> | 2023-02-26 01:04:34 +0100 |
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committer | GitHub <noreply@github.com> | 2023-02-25 16:04:34 -0800 |
commit | 35a279ecb9af41a6f95ddbc6a0f1beaa2472d165 (patch) | |
tree | be560e7396e5bc67c62e83e8d64c27cbefedf815 | |
parent | 1d012f46b0149cf718ca7fbd498e4b51b06bcd19 (diff) | |
download | pycparser-35a279ecb9af41a6f95ddbc6a0f1beaa2472d165.tar.gz |
_build_tables: Invalidate cache before importing generated modules (#494)
Make sure to invalidate finder caches before trying to import generated
modules. This is necessary according to the Python documentation:
https://docs.python.org/3/library/importlib.html#importlib.invalidate_caches
This fixes a hard-to-reproduce bug that Python would be unable to find
just-generated `lextab.py` if mtime of the current directory did not
change from the moment the script was started. This could
e.g. be the case if one has second-precision timestamps and removes
the generated file just before starting the build, e.g.:
$ rm pycparser/lextab.py; python -m build -nw
It could also be reproduced easier by doing something like:
$ cd pycparser
$ touch .; python -B _build_tables.py
Traceback (most recent call last):
File "/var/tmp/pycparser/pycparser/_build_tables.py", line 38, in <module>
import lextab
ModuleNotFoundError: No module named 'lextab'
This is because the first command (`rm` or `touch`) updates the mtime
of the directory to the current time. If the script is run fast enough,
it manages to scan the directory and then write the new `lextab.py`
within the same second. As a result, mtime of the directory after
writing the new file is the same as when the script was started, finder
does not invalidate the cache and assumes that `lextab.py` does not
exist since it did not exist when the directory was scanned earlier.
This potentially fixes #493.
It was originally reported on https://bugs.gentoo.org/701878.
Thanks to Gary E. Miller for patience in reproducing the problem
and proxy-debugging it for me, as well as testing the final patch before
submission.
-rw-r--r-- | pycparser/_build_tables.py | 3 |
1 files changed, 3 insertions, 0 deletions
diff --git a/pycparser/_build_tables.py b/pycparser/_build_tables.py index 958381a..4f37107 100644 --- a/pycparser/_build_tables.py +++ b/pycparser/_build_tables.py @@ -13,6 +13,7 @@ # Insert '.' and '..' as first entries to the search path for modules. # Restricted environments like embeddable python do not include the # current working directory on startup. +import importlib import sys sys.path[0:0] = ['.', '..'] @@ -32,6 +33,8 @@ c_parser.CParser( # Load to compile into .pyc # +importlib.invalidate_caches() + import lextab import yacctab import c_ast |