what exactly does typedef struct do? i.e. typedef struct { qboolean valid; int serverframe; int servertime; int deltaframe; byte areabits[MAX_MAP_AREAS/8]; player_state_t playerstate; int num_entities; int parse_entities; } frame_t; (taken from the Quake 2 source)

In C, typedef''ing a struct allows you to use the new name instead of "struct structname varname".




Basically, the typdef allows you to eliminate the "struct" part of the variable declaration. IIRC, this is not necessary in C++ - the "struct" keyword is not needed in variable declarations.

Hope this helps.

Ken Murphy

In C++, this:

typedef struct
{
} some_name;

is the same as this:

struct some_name
{
};

but the later is BY FAR the prefered way to do it.

as the first replied said ... this is an old C convention, because in C ... if you do this:

struct some_name
{
};

then when you declare varaibles you have to qualify them by telling the compiler it''s a struct name ... like this:

int x;
struct some_name myStruct;

but in C++ ... you NEVER use the word struct or class in that way, so the typedef around a struct or class declaration is really not used.

also .. note, there is no magic going on here .. what you are seeing is just a struct declaration, nested in a normal typedef. It would be the same as doing this as well:

struct some_struct
{
};

typedef some_struct another_struct;

in C .. to declare these as variables you would do it like this:

struct some_struct a;
another_struct b;

but in C++, they would both be:

some_struct a;
another_struct b;

... and to the ass who assumed you don''t know structs just because you don''t know why someone would use an outdated C syntax when declaring them ... say something usefull for a change.