28 Regular expressions library [re]

28.5 Namespace std::regex_constants [re.const]

28.5.3 Implementation-defined error_type [re.err]

namespace std {
  namespace regex_constants {
    typedef T3 error_type;
    static constexpr error_type error_collate = unspecified;
    static constexpr error_type error_ctype = unspecified;
    static constexpr error_type error_escape = unspecified;
    static constexpr error_type error_backref = unspecified;
    static constexpr error_type error_brack = unspecified;
    static constexpr error_type error_paren = unspecified;
    static constexpr error_type error_brace = unspecified;
    static constexpr error_type error_badbrace = unspecified;
    static constexpr error_type error_range = unspecified;
    static constexpr error_type error_space = unspecified;
    static constexpr error_type error_badrepeat = unspecified;
    static constexpr error_type error_complexity = unspecified;
    static constexpr error_type error_stack = unspecified;
  }
}
1

The type error_type is an implementation-defined enumerated type ([enumerated.types]). Values of type error_type represent the error conditions described in Table [tab:re:errortype]:

Table 140 — error_type values in the C locale
ValueError condition
error_collate The expression contained an invalid collating element name.
error_ctype The expression contained an invalid character class name.
error_escape The expression contained an invalid escaped character, or a trailing escape.
error_backref The expression contained an invalid back reference.
error_brack The expression contained mismatched [ and ].
error_paren The expression contained mismatched ( and ).
error_brace The expression contained mismatched { and }
error_badbrace The expression contained an invalid range in a {} expression.
error_range The expression contained an invalid character range, such as [b-a] in most encodings.
error_space There was insufficient memory to convert the expression into a finite state machine.
error_badrepeat One of *?+{ was not preceded by a valid regular expression.
error_complexity The complexity of an attempted match against a regular expression exceeded a pre-set level.
error_stack There was insufficient memory to determine whether the regular expression could match the specified character sequence.