How to handle typedef datatypes in C (generally speaking)?

Question

Basically the compiler complains of unknown type name 'Song_t' since the datatype definition happens after it is first referenced.

struct Cell { Song_t song;
            struct Cell *pnext;
};

typedef struct Song Song_t;

If I place the typedef before, it works. Is it therefore generally advised to place typedefs at the very beginning of each file?

Answer 1

Is it therefore generally advised to place typedefs at the very beginning of each file?

Not necessarily, and you could avoid typedef -s by coding

struct Cell { 
    struct Song song;
    struct Cell *pnext;
};

Of course, struct Song should be defined "before" (take into account the C preprocessor).

You could also code

typedef struct Song Song_t;
typedef struct Cell Cell_t;

and use later only Song_t etc. You do have to provide (later) a definition of struct Song (not just a forward declaration). For details, read Modern C, see this C reference website, and the C11 standard n1570.

Look for inspiration into the source code of the Linux kernel or of a simple C compiler, such as nwcc, or of the GTK toolkit. All these are coded (mostly) in C. Look also for examples on github. Study also the source code of GCC. It is a popular C compiler (and old versions of it -e.g. GCC 4.4- have been coded in C mostly).