Standard for typedef'ing

Question

Hello,

gcc 4.4.4 c89

I am just wondering is there any standard that should be followed when creating types.

for example:

typedef struct date
{
} date_t;

I have also seen people put a capital like this:

typedef struct date
{
} Date;

Or for variables

typedef unsigned int Age;

or this

typedef unsigned int age_t;

Is there any standard that should be followed. Personally I prefer post fixing with a _t.

Many thanks for any suggestions,

Answer 1

Style is a very personal and highly subjective thing, I strongly urge you to just use whatever you like, or whatever conventions are used in your organization.

Answer 2

Follow what the rest of the people do for your project so everything stays consistent. Otherwise they're both acceptable technically.

Answer 3

If you are working on a platform that follows POSIX standards you should be aware that any identifier ending in _t is reserved for POSIX defined types so it is not advisable to follow the same convention for your own types.

Answer 4

Much of this comes down to personal preference, with the key being to be consistent (or if you have a company convention, use that). The following article has some naming guides:

http://www.montefiore.ulg.ac.be/~piater/Cours/Coding-Style/

Note that it switches the '_t' portion:

typedef struct node_t {
  void *content;
  struct node_t *next;
} Node;

typedef enum season_t { SPRING, SUMMER, FALL, WINTER } Season;

There was an earlier discussion on C naming conventions here:

http://stackoverflow.com/questions/1722112/what-are-the-most-common-naming-conventions-in-c

Answer 5

I don't think there is any "standard" naming convention. In fact, they vary so wildly between projects (and also between other languages like C++ or Java) that I've personally adopted camelCase in all languages.

I always define my structures through typedef, so I just use whatever name I would have given it otherwise (this is also what the Win32 API does). In case I need a self-referencing structure, I prefix an _ to the raw struct's name:

typedef struct _Node {
  _Node *next;
} Node;

Answer 6

In general most languages allow the use of SentenceCase for non-standardized classes or types. I find this is the best practise, and in languages that allow it, additionally use namespaces or modules to prevent clashes. In languages that don't (such as C), a prefix where necessary never goes astray. To use a multi-language example for something I'm currently working on:

C: typedef uint32_t CpfsMode;
C++: namespace Cpfs { typedef uint32_t Mode; }
Python: cpfs.Mode = int

Answer 7

You may just simply use

typedef struct toto toto;

1. The struct toto (tag) and the typedef name toto (identifier) are in different C "namescopes" so they are compatible, but they pooint to the same type in the end.
2. As an extra bonus this is also compatible with C++, which usually implicitly has such a typedef.
3. As another bonus this inhibits to declare a variable toto which can be quite confusing at times.