struct

[jorz]

Hi all,

what is the difference between

struct my_struct
{
   int one;
   int two;
};

and

typedef struct
{
  int one;
  int two;
} my_struct;

many thanks,

[gelatine]

http://en.wikipedia.org/wiki/Typedef
alot there about typedef.

[Peter87]

The second way is often used in C. I don't know the details but if you did the first one in C you would have to write struct my_struct in a lot of places instead of just my_struct. Example: To define a variable named foo of type my_struct you would have to write struct my_struct foo; instead of just my_struct foo;

In C++ there is no need to use the typedef version because you can always use my_struct without struct in front.

[MrHutch]

Yeah, basically what Peter87 said. The latter method is C code and isn't really used as much in C++. The former is generally preferred.

[vlad from moscow]

There are many details that you should take into account. I will show at least two of them.
For example in the first definition the name of the structure is visible inside its definition and you can refer to it.

struct my_struct
{
   int one;
   int two;
   my_struct *next;
};

In the second declaration you can not do so because the typedef name is not visible inside the definition of the structure.

typedef struct
{
   int one;
   int two;
   my_struct *next;   // compilation error  
} my_struct;

Another example. You can redeclare a name of a structure but you can not redeclare a typedef name with another type.

struct my_struct
{
   int one;
   int two;
};

int my_struct;

struct my_struct str;

typedef struct
{
   int one;
   int two;
} my_struct;

int my_struct; // compilation error

my_struct str; // compilation error