If I do a `typedef` in C or C++, when should I add `_t` at the end of typedef'ed type? [duplicate]

Question

I am confused when should I add the trailing _t to typedef'ed types?

For example, should I do this:

typedef struct image image_t; 

or this:

typedef struct image image; 

What are the general rules?

Another example, should I do this:

typdef enum { ARRAY_CLOSED, ARRAY_OPEN, ARRAY_HALFOPEN } array_type_t; 

or this:

typdef enum { ARRAY_CLOSED, ARRAY_OPEN, ARRAY_HALFOPEN } array_type; 

Please enlighten me.

Thanks, Boda Cydo.

Answer 1

In POSIX, names ending with _t are reserved, so if you are targeting a POSIX system (e.g., Linux), you should not end your types with _t.

Answer 2

I personally despise the _t convention. So long as you are consistent, it really does not matter, however.

Note that (as other answers here indicate) if you are coding to some other standard, such as POSIX, you need to check if it's okay in that standard before using such names.