contrib/fuzz/pyutil.cc

copyfiles: deal with existing file when hardlinking

If the hardlinking fails, we fallback to `shutil.copy`, but do not consider
future hardlinking doomed.

This is a slight improvement from the current situation, we still avoid
hardliking in a case we might be able to do it. However this does not have an
impact of the rest of the operation.

(This is an opportunity improvement while looking at something next to that.)

Differential Revision: https://phab.mercurial-scm.org/D10841

#include "pyutil.h"

#include <iostream>
#include <string>

namespace contrib
{

#if PY_MAJOR_VERSION >= 3
#define HG_FUZZER_PY3 1
PyMODINIT_FUNC PyInit_parsers(void);
#else
PyMODINIT_FUNC initparsers(void);
#endif

static char cpypath[8192] = "\0";

static PyObject *mainmod;
static PyObject *globals;

void initpy(const char *cselfpath)
{
#ifdef HG_FUZZER_PY3
	const std::string subdir = "/sanpy/lib/python3.8";
#else
	const std::string subdir = "/sanpy/lib/python2.7";
#endif

	/* HACK ALERT: we need a full Python installation built without
	   pymalloc and with ASAN, so we dump one in
	   $OUT/sanpy/lib/python2.7. This helps us wire that up. */
	std::string selfpath(cselfpath);
	std::string pypath;
	auto pos = selfpath.rfind("/");
	if (pos == std::string::npos) {
		char wd[8192];
		if (!getcwd(wd, 8192)) {
			std::cerr << "Failed to call getcwd: errno " << errno
			          << std::endl;
			exit(1);
		}
		pypath = std::string(wd) + subdir;
	} else {
		pypath = selfpath.substr(0, pos) + subdir;
	}
	strncpy(cpypath, pypath.c_str(), pypath.size());
	setenv("PYTHONPATH", cpypath, 1);
	setenv("PYTHONNOUSERSITE", "1", 1);
	/* prevent Python from looking up users in the fuzz environment */
	setenv("PYTHONUSERBASE", cpypath, 1);
#ifdef HG_FUZZER_PY3
	std::wstring wcpypath(pypath.begin(), pypath.end());
	Py_SetPythonHome(wcpypath.c_str());
#else
	Py_SetPythonHome(cpypath);
#endif
	Py_InitializeEx(0);
	mainmod = PyImport_AddModule("__main__");
	globals = PyModule_GetDict(mainmod);

#ifdef HG_FUZZER_PY3
	PyObject *mod = PyInit_parsers();
#else
	initparsers();
	PyObject *mod = PyImport_ImportModule("parsers");
#endif

	PyDict_SetItemString(globals, "parsers", mod);
}

PyObject *pyglobals()
{
	return globals;
}

} // namespace contrib