CODEWITHSUNDEEP
cdata-structuresstruct
nowox
nowox

Reputation: 29096

Naming standards for C unions

I sometime use unions to access the same type of data differently. For example this union: 

typedef union {
   int64 word;
   int32 array[2];
   struct {
      field4:16;
      field3:16;
      field2:28;
      field1:4;
   } bit;
} my_type;

Is this solution consensually correct and is there any standards for the names I used (word, array, bit)?

The bad point with this solution is the cumbersome notation I got:

   my_type data;
   data.bit.field1 = 0xA;
   for(i=0;i<sizeof(my_t);i++)
      data.array[i]++;

Upvotes: 1

Views: 1465

Answers (1)

harper
harper

Reputation: 13690

Some compilers allow to omit the name of struct in a union. You can try to define your type as this:

typedef union {
   int64 word;
   int32 array[2];
   struct {
      field4:16;
      field3:16;
      field2:28;
      field1:4;
   } bit;
} my_type;

This allows to access the bit members a bit easier:

my_type data;
data.field1 = 0xA;

But unfortunately this is compiler and compiler options dependent. Edit: The C11 Standard draft describes this as anonymous struct.

Upvotes: 3

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