Thread: Help with nested struct pointers

I am tasked with writitng a program that populates a data file based on the contents of structures defined in a library. Below are the structures.

Code:

struct simrad_struct
{
int num_records;
...
struct simrad_record_struct * recs;
}

struct simrad_record_struct
{
long id;
....
long office_num
}

I cannot change these structures to typedefs since they are in a library.

My program has a function which takes in a populated simrad struct:

Code:

int (char * sim)
{
struct simrad_struct * sim_pop;
sim2_pop = (struct simrad_struct *) sim;

.....
return 0;
}

what I need to do is access the value of office_num, in the nested struct.

Code:

long office =  sim2_pop->recs->office_num;

gives the error "dereferencing pointer to incomplete type".

Does anyone know how I can access this value?

note that the following code works.

Code:

int num = sim2_pop->num_records;

Looks like the simrad_record_struct type is incomplete at the time you attempt to access the ->rec member. Meaning it's been forward-declared but never defined. Make sure you're including all the relevant header files (in your code, as well as in this discussion)

Are you SURE that the definition of simrad_record_struct is in the file simrad.h? Is it possibly surrounded by an #if or #ifdef which is turning the definition off for some reason?

Also I hope you have "" or <> around that include -- didn't show up in your post. Obviously, you need one of those.

I even tried the following. The first line compiles but the second has the same isseu as before

That proves that simrad_record_struct has been forward declared like this:

Code:

struct simrad_record_struct;

But the actual definition (the members of the struct) is not available.

I have the "" around the include just fogot to type it.

I am lookingat the file and the structs are both in there. The file basically contains a series of structs of the form

Code:

struct <name>
{
}

There are no conditional statements to turn the various structs on and off. Basically simrad_struct includes a pointer to each of the other structs as well as some standard members (int, long, etc...). They are all forward declared so I dont understand why I am access simrad_struct but not simrad_record_struct since they were both forward declared.

Except for the missing semicolons on the end of all the struct definitions (did you just forget to type them, too?) I see nothing wrong. Unless you can post the full header file I'm stumped.

Code:

int date = sime2_pop->record->png_date;

Kurt

Originally Posted by vampireiam

int date = sime2_pop->record.png_date; // this gets the error mentioned.

This should be:

Code:

int date = sim2_pop->record->png_date;

Me and my stupid typos.

I meant that

Code:

int date = sim2_pop->record->png_date;   //does not work

I have verified that it isnt how the structs are declared or how I am attepmting to access the field in the nested struct. I did a simple example and got everything to work using the structs as defined above. There are some other declerations in the .h file that appear to be causing the issue.