contrib/fuzz/fm1readmarkers.cc

resolve: use the `parentchange` context manager to apply merge action

In an ideal world, we would not have to do that. However, we are miles away from
being ready to not have to do it.

So we add this context manager alongside a long comment. This will help use to
get to the point were have two distinct API with strict rules about when to call
them.

Differential Revision: https://phab.mercurial-scm.org/D11074

#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.
}
}