C error : elements of array have incomplete type

[Tacitus]

Hi,

I am facing following error message while compiling a souce code:

error: elements of array `runparts_long_options' have incomplete type:

The error is coming from following code statements:

// run_parts.c file
static const struct option runparts_long_options[] = {
{ "test", 0, NULL, 't' },
{ "umask", 1, NULL, 'u' },
{ "arg", 1, NULL, 'a' },
{ 0, 0, 0, 0 }
};

struct option // getopt.h file
{
const char *name;
/* has_arg can't be an enum because some compilers complain about
type mismatches in all the code that assumes it is an int. */
int has_arg;
int *flag;
int val;
};

I'm unable to spot the error cause in this.
Can somebody help me out on this?

Thanks!
Tacitus

[Banfa]

I would suggest that you probably have failed to include getopt.h before you declare your array but have forward decalred the structure name i.e.

struct option;
 
// run_parts.c file
static const struct option runparts_long_options[] = {
    { "test", 0, NULL, 't' },
    { "umask", 1, NULL, 'u' },
    { "arg", 1, NULL, 'a' },
    { 0, 0, 0, 0 }
};
 

You have told it that a structure called option exists but not defined that structure. It then can not make an array of these structures as it does not know their size and therefore how much memory to allocate.

Forward declaring a structure is useful if you want to declare a pointer to that structure. This can be useful for returning a pointer from a library function without letting the calling code have visibility of the structure definition.