fuzz: move many initialization steps into LLVMFuzzerInitialize

Doing this means that things we intentionally leak (eg type objects)
no longer confuse AddressSanitizer, so now we can run the fuzzer MUCH
longer.

Differential Revision: https://phab.mercurial-scm.org/D5154

contrib/fuzz/manifest.cc

@@ -1,81 +1,83 b''
 #include <Python.h>
 #include <assert.h>
 #include <stdlib.h>
 #include <unistd.h>
 
 #include <string>
 
 extern "C" {
 
 /* TODO: use Python 3 for this fuzzing? */
 PyMODINIT_FUNC initparsers(void);
 
 static char cpypath[8192] = "\0";
 
+static PyCodeObject *code;
+static PyObject *mainmod;
+static PyObject *globals;
+
 extern "C" int LLVMFuzzerInitialize(int *argc, char ***argv)
 {
 	const std::string subdir = "/sanpy/lib/python2.7";
 	/* 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(*argv[0]);
 	std::string pypath;
 	auto pos = selfpath.rfind("/");
 	if (pos == std::string::npos) {
 		char wd[8192];
 		getcwd(wd, 8192);
 		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);
 	Py_SetPythonHome(cpypath);
 	Py_InitializeEx(0);
-	return 0;
-}
-
-int LLVMFuzzerTestOneInput(const uint8_t *Data, size_t Size)
-{
 	initparsers();
-	PyObject *mtext =
-	    PyBytes_FromStringAndSize((const char *)Data, (Py_ssize_t)Size);
-	PyObject *mainmod = PyImport_AddModule("__main__");
-	PyObject *globals = PyModule_GetDict(mainmod);
-	PyObject *locals = PyDict_New();
-	PyDict_SetItemString(locals, "mdata", mtext);
-	PyCodeObject *code =
-	    (PyCodeObject *)Py_CompileString(R"py(
+	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);
+	mainmod = PyImport_AddModule("__main__");
+	globals = PyModule_GetDict(mainmod);
+	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, globals, locals);
 	if (!res) {
 		PyErr_Print();
 	}
 	Py_XDECREF(res);
-	Py_DECREF(code);
 	Py_DECREF(locals);
 	Py_DECREF(mtext);
 	return 0; // Non-zero return values are reserved for future use.
 }
 }