Mikroelektronika MIKROE-738 Datenbogen

mikroC PRO for PIC32

MikroElektronika

217

Anonymous Unions

Anonymous unions are unions that are declared without

 tag

 or 

declarator

:

union { member-declarator-list };

Such union declarations do not declare 

; they declare an unnamed 

The name of each union member must be unique within the scope where the union is declared.

In C, an anonymous union can have a tag; it cannot have declarators. Names declared in an anonymous union are 

used directly, like nonmember variables.

In addition to the restrictions listed above in Union, anonymous unions are subject to additional restrictions:

 

- They must also be declared as 

static

 if declared in global scope. If declared in local scope, they must be  

 

  either 

static

 or 

automatic

, not 

external

 

 

- They can have only public members; private and protected members in anonymous unions generate  

 

  errors. 

 

- They cannot have function members. 

Here is a simple example:

union {    // no union tag

  int i;

  float f;

  union {  // no union tag 

    unsigned char uc;

    char c;

  };       // no declarator

};         // no declarator

Anonymous Union Member Access

Anonymous union members are accessed directly because they are in the scope containing the anonymous union:

i = 1;

f = 3.14;

uc = ‘c’;

c  = ‘u’;