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

@@ -12,6 +12,10 b' 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";
@@ -35,20 +39,8 b' extern "C" int LLVMFuzzerInitialize(int '
 	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)
@@ -67,13 +59,23 b' except Exception as e:'
   # to debug failures.
   # print e
 )py",
-	                                     "fuzzer", Py_file_input);
+	                                        "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.