view contrib/fuzz/manifest.cc @ 41247:a89b20a49c13

rust-cpython: using MissingAncestors from Python code

As precedently done with LazyAncestors on cpython.rs, we test for the
presence of the 'rustext' module.

incrementalmissingrevs() has two callers within the Mercurial core:
`setdiscovery.partialdiscovery` and the `only()` revset.

This move shows a significant discovery performance improvement
in cases where the baseline is slow: using perfdiscovery on the PyPy
repos, prepared with `contrib/discovery-helper <repo> 50 100`, we
get averaged medians of 403ms with the Rust version vs 742ms without
(about 45% better).

But there are still indications that performance can be worse in cases
the baseline is fast, possibly due to the conversion from Python to
Rust and back becoming the bottleneck. We could measure this on
mozilla-central in cases were the delta is just a few changesets.
This requires confirmation, but if that's the reason, then an
upcoming `partialdiscovery` fully in Rust should solve the problem.

Differential Revision: https://phab.mercurial-scm.org/D5551

#include <Python.h>
#include <assert.h>
#include <stdlib.h>
#include <unistd.h>

#include "pyutil.h"

#include <string>

extern "C" {

static PyCodeObject *code;

extern "C" int LLVMFuzzerInitialize(int *argc, char ***argv)
{
	contrib::initpy(*argv[0]);
	code = (PyCodeObject *)Py_CompileString(R"py(
from parsers import lazymanifest
try:
  lm = lazymanifest(mdata)
  # iterate the whole thing, which causes the code to fully parse
  # every line in the manifest
  list(lm.iterentries())
  lm[b'xyzzy'] = (b'\0' * 20, 'x')
  # do an insert, text should change
  assert lm.text() != mdata, "insert should change text and didn't: %r %r" % (lm.text(), mdata)
  del lm[b'xyzzy']
  # 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)
{
	PyObject *mtext =
	    PyBytes_FromStringAndSize((const char *)Data, (Py_ssize_t)Size);
	PyObject *locals = PyDict_New();
	PyDict_SetItemString(locals, "mdata", mtext);
	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.
}
}