Handle regex syntax errors at runtime.

libc.regex_match() now raises RuntimeError if the regex can't be
compiled by regcomp().

core/expr_eval.py

@@ -606,13 +606,10 @@ def Eval(self, node):
          return s1 != s2

        if op_id == Id.BoolBinary_EqualTilde:
          matches = libc.regex_match(s2, s1)

          # NOTE: regex matching shouldn't fail if compilation succeeds.
          if matches == -1:
            raise AssertionError(
                "Invalid regex %r: should have been caught at compile time" %
                s2)
          try:
            matches = libc.regex_match(s2, s1)
          except RuntimeError:
            e_die("Invalid regex %r", s2, word=node.right)

          if matches is None:
            return False

native/libc.c

@@ -246,8 +246,8 @@ func_regex_match(PyObject *self, PyObject *args) {
  regex_t pat;
  if (regcomp(&pat, pattern, REG_EXTENDED) != 0) {
    // When the regex contains a variable, it can't be checked at compile-time.
    fprintf(stderr, "Invalid regex at runtime\n");
    return PyLong_FromLong(-1);
    PyErr_SetString(PyExc_RuntimeError, "Invalid regex syntax (func_regex_match)");
    return NULL;
  }

  int outlen = pat.re_nsub + 1;
@@ -334,8 +334,8 @@ static PyMethodDef methods[] = {
  {"regex_parse", func_regex_parse, METH_VARARGS,
   "Compile a regex in ERE syntax, returning whether it is valid"},
  {"regex_match", func_regex_match, METH_VARARGS,
   "Match regex against a string.  Returns a list of matches, None if no match, or "
    "-1 if the regex is invalid."},
   "Match regex against a string.  Returns a list of matches, None if no match. "
    "Raises RuntimeError if the regex is invalid."},
  {"regex_first_group_match", func_regex_first_group_match, METH_VARARGS,
   "If the regex matches the string, return the start and end position of the "
   "first group.  None for no match; -1 for invalid regex."},

native/libc_test.py

@@ -75,7 +75,8 @@ def testRegex(self):
      self.assertEqual(expected, actual)

    # Error.
    print(libc.regex_match(r'*', 'abcd'))
    self.assertRaises(
        RuntimeError, libc.regex_match, r'*', 'abcd')

  def testRegexFirstGroupMatch(self):
    s='oXooXoooXoX'