C naming suggestion for Error Code enums

Question

I'm writing a simple parser to read the config file.The config.h interface have only three main functions they are in brief as follows,

config_init();
config_dinit();
config_parse();
config_read_value();

My question is those functions will emit different type of errors , for a example,

config_init() emit , FILE_NOT_FOUND,FILE_EOF_ERROR,FILE_OPEN_ERROR, ...
config_dinit() emit , NOT_INIT_ERROR ,
config_parse() emit , PARSE_ERROR, OVERFLOW_ERROR, INVALID_CHARACTER_FOUND_ERROR,...
config_read_value() emit, SECTION_NOT_FOUND,KEYWORD_NOT_FOUND,OVERFLOW_ERROR,NOT_INITIALIZED_ERROR,INVALID_STATE_ERROR,... etc.

Then I create enums for each function, for by using these names , 
enum Config_ParseError{...} , enum Config_InitError{...} ,enum Config_ReadValueError{..}
etc.

Some enum values are overlapping each other and hit "compiler error" too. like OVERFLOW_ERROR,

I'm opening for your suggestions,

and I have done a quick research on the google and found that most popular IRC client source code have defined the enums like this,

enum {
    CMDERR_OPTION_UNKNOWN = -3, /* unknown -option */
    CMDERR_OPTION_AMBIGUOUS = -2, /* ambiguous -option */
    CMDERR_OPTION_ARG_MISSING = -1, /* argument missing for -option */

    CMDERR_UNKNOWN, /* unknown command */
    CMDERR_AMBIGUOUS, /* ambiguous command */

        CMDERR_ERRNO, /* get the error from errno */
    CMDERR_NOT_ENOUGH_PARAMS, /* not enough parameters given */
    CMDERR_NOT_CONNECTED, /* not connected to server */
    CMDERR_NOT_JOINED, /* not joined to any channels in this window */
    CMDERR_CHAN_NOT_FOUND, /* channel not found */
    CMDERR_CHAN_NOT_SYNCED, /* channel not fully synchronized yet */
    CMDERR_ILLEGAL_PROTO, /* requires different chat protocol than the active server */
    CMDERR_NOT_GOOD_IDEA, /* not good idea to do, -yes overrides this */
    CMDERR_INVALID_TIME, /* invalid time specification */
    CMDERR_INVALID_CHARSET, /* invalid charset specification */
    CMDERR_EVAL_MAX_RECURSE, /* eval hit recursion limit */
    CMDERR_PROGRAM_NOT_FOUND /* program not found */
};

it defines enum without any name, is that a good style?Then why what are the reasons for that?

Seriously need some more good naming decisions. Please don't hurt me I just only start reading "writing beautiful C code" book.

Thanks In Advance. Sandun.

Answer 1

I'm usually a fan of one set of error returns for an entire library. This way in consumers they don't have to worry about "was the -1 bad input to X or could not connect to Y".

I'm also a fan of E_ prefixes, but really any will do:

enum _config_error
{
    E_SUCCESS = 0,
    E_INVALID_INPUT = -1,
    E_FILE_NOT_FOUND = -2, /* consider some way of returning the OS error too */
    ....
};

/* type to provide in your API */
typedef enum _config_error error_t;

/* use this to provide a perror style method to help consumers out */
struct _errordesc {
    int  code;
    char *message;
} errordesc[] = {
    { E_SUCCESS, "No error" },
    { E_INVALID_INPUT, "Invalid input" },
    { E_FILE_NOT_FOUND, "File not found" },
    ....
};