In C, can `enum` be made to count backward?

Question

I would like to create an enumerated list of negative values for error handling so <0 is an error and >=0 is valid for some function:

int f() {
  if (someerror())
    return ERR_TYPE_2;
  else
    return 0;
}

main() {
  if (f() < 0) blow_up(); 
  else profit(); 
}

I know that enumerations in C (enum) count up from 0 by default, and I could assign them like so:

enum {
  ERR_TYPE_1 = -1,
  ERR_TYPE_2 = -2,
  ERR_TYPE_3 = -3
}

or I get arbitrary negative enums "automatically" by starting at an arbitrary negative value for which the enum will never reach:

enum {
  ERR_TYPE_1 = -100,
  ERR_TYPE_2 // -99
  ERR_TYPE_3 // -98 ...
}

Question: Is there a way to tell enum to start at -1 and count negative instead of using the methods above?

Update for commenters:

I have no objection to hard-coded error values, in fact that's what I usually do (either as a define or an enum).

This question is really about whether C officially supports negative enums in some unknown-to-me syntactic sugar that wasn't forthcoming after some search-fu.

Answer 1

What you want is not possible. Enum identifiers without an explicit value assigned are required to have the value of 1 more that the prior identifier, or 0 for the first one.

This is spelled out in section 6.7.2.2p3 of the C standard regarding Enumeration Specifiers:

If the first enumerator has no =, the value of its enumeration constant is 0. Each subsequent enumerator with no = defines its enumeration constant as the value of the constant expression obtained by adding 1 to the value of the previous enumeration constant.

While it's possible that a compiler may support a different ordering as an extension, I'm not aware of any that support such a feature.