C Variable has incomplete initializer

Question

I am trying to make a struct with a default value, as described here: Default values in a C Struct. However, I have this C code, inside a header file:

/* tokens.h */
typedef struct {
    char *ID;
    char *KEY;
    char *TYPE;
} tokens;

const struct tokens TOKENS_DFLT = {
    "id",
    "key",
    "type"
};

And I am getting an error on line 7 saying:

error: variable 'TOKENS_DFLT' has initializer but incomplete type

Can anyone please explain to me what this problem is and how I can fix it and prevent it in the future?

walkytalky · Accepted Answer · 2010-11-18 13:57:40Z

3

You haven't defined struct tokens. You've defined an unnamed struct and simultaneously typedef-ed it to the type name tokens.

If you had instead defined

typedef struct tokens_ {
    char *ID;
    char *KEY;
    char *TYPE;
} tokens;

Then you could declare your constant as either:

const struct tokens_ TOKENS_DFLT = { ... };

Or

const tokens TOKENS_DFLT = { ... };

As it is, you're between two stools.

answered Nov 18, 2010 at 13:57

walkytalky

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1 Comment

Richard J. Ross III Over a year ago

now i get a warning: Useless storage class specifier in empty declaration

unwind · Accepted Answer · 2010-11-18 13:58:44Z

2

This:

const struct tokens TOKENS_DFLT = {
    "id",
    "key",
    "type"
};

should be:

const tokens TOKENS_DFLT = {
    "id",
    "key",
    "type"
};

Since you've defined the name tokens to mean struct tokens.

answered Nov 18, 2010 at 13:58

unwind

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