New submission from Sye van der Veen:
The PyMarshal_Read* functions raise EOFError when the end of the file is
unexpectedly met. The current import.c functions propagate this error when
reading .pyc or .pyo files. One consequence of this is that Python will abort
on startup if, say, encodings.utf_8's .pyc file is truncated.
I have encountered a scenario where this truncation is common. If a second
Python process is launched while the first is writing the "core" .pyc files,
the second process may open the files before they are completely written and
will thus see truncated files and abort. This is a race condition that I was
able to reproduce consistently on several Windows Server 2008 RC2 Standard SP1
machines running 32-bit Python 3.2.3 from GNU make with "-j 16" (Intel Xeon
E5405 2GHz 2 processors 8GB 64-bit OS). (Of course, I had to clean the
__pycache__ directories between tests.)
This can be fixed in load_source_module by making read_compiled_module failures
non-fatal:
if (cpathname != NULL &&
(fpc = check_compiled_module(pathname, st.st_mtime, cpathname))) {
co = read_compiled_module(cpathname, fpc);
if (co == NULL) PyErr_Clear();
fclose(fpc);
}
if (co != NULL) {
// etc...
}
else {
co = parse_source_module(pathname, fp);
// etc...
write_compiled_module(co, cpathname, &st);
}
This is similar to how write_compiled_module ignores failures in writing the
.pyc files. It ensures that if the .pyc file is corrupt for _any_ reason, it
will get rewritten; this could be made specific to EOFError, but I don't
recommed that. Mostly, it ensures that corrupt .pyc files do not prevent
Python from loading if the .py files are valid.
----------
components: None
messages: 174438
nosy: syeberman
priority: normal
severity: normal
status: open
title: import.c doesn't handle EOFError from PyMarshal_Read*
type: crash
versions: Python 3.2
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Python tracker <rep...@bugs.python.org>
<http://bugs.python.org/issue16384>
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