contrib/fuzz/fm1readmarkers.cc

tests-pure: fixing test-parseindex2

This is a followup to D7603 (49fa0b31ee1d) which broke
the tests for pure Python implementation. There are two
divergences between pure and C implementations:

- the pure implementation would accept only -1 as slice end,
  whereas C accepts both -1 and len(index)
- in pure Python, `headrevs` is provided by revlog.py, not
  by the index.

Differential Revision: https://phab.mercurial-scm.org/D7707

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

#include <string>

#include "pyutil.h"

extern "C" {

static PYCODETYPE *code;

extern "C" int LLVMFuzzerInitialize(int *argc, char ***argv)
{
	contrib::initpy(*argv[0]);
	code = (PYCODETYPE *)Py_CompileString(R"py(
def maybeint(s, default):
    try:
        return int(s)
    except ValueError:
        return default
try:
    parts = data.split('\0', 2)
    if len(parts) == 3:
        offset, stop, data = parts
    elif len(parts) == 2:
        stop, data = parts
        offset = 0
    else:
        offset = stop = 0
    offset, stop = maybeint(offset, 0), maybeint(stop, len(data))
    parsers.fm1readmarkers(data, offset, stop)
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 *text =
	    PyBytes_FromStringAndSize((const char *)Data, (Py_ssize_t)Size);
	PyObject *locals = PyDict_New();
	PyDict_SetItemString(locals, "data", text);
	PyObject *res = PyEval_EvalCode(code, contrib::pyglobals(), locals);
	if (!res) {
		PyErr_Print();
	}
	Py_XDECREF(res);
	Py_DECREF(locals);
	Py_DECREF(text);
	return 0; // Non-zero return values are reserved for future use.
}
}