procutil: make stream detection in make_line_buffered more correct and strict
In make_line_buffered(), we don’t want to wrap the stream if we know that lines
get flushed to the underlying raw stream already.
Previously, the heuristic was too optimistic. It assumed that any stream which
is not an instance of io.BufferedIOBase doesn’t need wrapping. However, there
are buffered streams that aren’t instances of io.BufferedIOBase, like
Mercurial’s own winstdout.
The new logic is different in two ways:
First, only for the check, if unwraps any combination of WriteAllWrapper and
winstdout.
Second, it skips wrapping the stream only if it is an instance of io.RawIOBase
(or already wrapped). If it is an instance of io.BufferedIOBase, it gets
wrapped. In any other case, the function raises an exception. This ensures
that, if an unknown stream is passed or we add another wrapper in the future,
we don’t wrap the stream if it’s already line buffered or not wrap the stream
if it’s not line buffered. In fact, this was already helpful during development
of this change. Without it, I possibly would have forgot that WriteAllWrapper
needs to be ignored for the check, leading to unnecessary wrapping if stdout is
unbuffered.
The alternative would have been to always wrap unknown streams. However, I
don’t think that anyone would benefit from being less strict. We can expect
streams from the standard library to be subclassing either io.RawIOBase or
io.BufferedIOBase, so running Mercurial in the standard way should not regress
by this change. Py2exe might replace sys.stdout and sys.stderr, but that
currently breaks Mercurial anyway and also these streams don’t claim to be
interactive, so this function is not called for them.
#include <Python.h>
#include <assert.h>
#include <stdlib.h>
#include <unistd.h>
#include "FuzzedDataProvider.h"
#include "pyutil.h"
#include <string>
extern "C" {
static PYCODETYPE *code;
extern "C" int LLVMFuzzerInitialize(int *argc, char ***argv)
{
contrib::initpy(*argv[0]);
code = (PYCODETYPE *)Py_CompileString(R"py(
try:
lm = parsers.lazymanifest(mdata)
# iterate the whole thing, which causes the code to fully parse
# every line in the manifest
for e, _, _ in lm.iterentries():
# also exercise __getitem__ et al
lm[e]
e in lm
(e + 'nope') in lm
lm[b'xyzzy'] = (b'\0' * nlen, 'x')
# do an insert, text should change
assert lm.text() != mdata, "insert should change text and didn't: %r %r" % (lm.text(), mdata)
cloned = lm.filtercopy(lambda x: x != 'xyzzy')
assert cloned.text() == mdata, 'cloned text should equal mdata'
cloned.diff(lm)
del lm[b'xyzzy']
cloned.diff(lm)
# should be back to the same
assert lm.text() == mdata, "delete should have restored text but didn't: %r %r" % (lm.text(), mdata)
except Exception as e:
pass
# uncomment this print if you're editing this Python code
# to debug failures.
# print e
)py",
"fuzzer", Py_file_input);
return 0;
}
int LLVMFuzzerTestOneInput(const uint8_t *Data, size_t Size)
{
// Don't allow fuzzer inputs larger than 100k, since we'll just bog
// down and not accomplish much.
if (Size > 100000) {
return 0;
}
FuzzedDataProvider provider(Data, Size);
Py_ssize_t nodelength = provider.ConsumeBool() ? 20 : 32;
PyObject *nlen = PyLong_FromSsize_t(nodelength);
PyObject *mtext =
PyBytes_FromStringAndSize((const char *)Data, (Py_ssize_t)Size);
PyObject *locals = PyDict_New();
PyDict_SetItemString(locals, "mdata", mtext);
PyDict_SetItemString(locals, "nlen", nlen);
PyObject *res = PyEval_EvalCode(code, contrib::pyglobals(), locals);
if (!res) {
PyErr_Print();
}
Py_XDECREF(res);
Py_DECREF(locals);
Py_DECREF(mtext);
return 0; // Non-zero return values are reserved for future use.
}
}