Handle invalid non-ASCII struct formats in the fuzz harness

Author: pablogsal

Lib/test/test_xxtestfuzz.py

@@ -18,6 +18,7 @@ def test_sample_input_smoke_test(self):
         _xxtestfuzz.run(b"1")
         _xxtestfuzz.run(b"AAAAAAA")
         _xxtestfuzz.run(b"AAAAAA\0")
+        _xxtestfuzz.run(b"\xff\0")
 
 
 if __name__ == "__main__":

Modules/_xxtestfuzz/fuzzer.c

@@ -133,6 +133,10 @@ static int fuzz_struct_unpack(const char* data, size_t size) {
     if (unpacked == NULL && PyErr_ExceptionMatches(PyExc_SystemError)) {
         PyErr_Clear();
     }
+    /* Ignore any ValueError, these are triggered by non-ASCII format. */
+    if (unpacked == NULL && PyErr_ExceptionMatches(PyExc_ValueError)) {
+        PyErr_Clear();
+    }
     /* Ignore any struct.error exceptions, these can be caused by invalid
        formats or incomplete buffers both of which are common. */
     if (unpacked == NULL && PyErr_ExceptionMatches(struct_error)) {