Bit-field struct within bit-field struct in C

Question

I'm trying to find another way to create a bit-field structure within a bit-field structure in C.

Somewhat like this:

typedef struct
{
  int A : 16;
  int B : 16;
} Struct1;

typedef struct
{
  int A     : 16;
  Struct1 B : 32;
} Struct2;

But the C Compiler doesn't like it, and it has to be bit-field. A friend came up with using unions, but was wondering if someone knows another method besides using unions for this?

Thanks!

I'm translating code from ADA to C, and we're trying to do it as close as possible to the ADA as we can — Skynight, Sep 28 '13 at 22:44
@shunyo -- we did that for some structures, but can't do that will all of them — Skynight, Sep 28 '13 at 22:45
because Struct1 defines a bit field, In your second struct, if : 32; is replaced with ;, does Struct1 B; not also define a struct member that is a bit field? i.e.: `Struct2 abc;` `abc.A = 0x22;` `abc.B.A = 0x22;` and `abc.B.B = 0x44;` all seem to accept values and are useable like a bitfield. — ryyker, Sep 28 '13 at 23:00

ryyker · Answer 1 · 2015-01-06T03:19:54.240

1

If I do this:

typedef struct
{
  int A : 16;
  int B : 16;
} Struct1;

typedef struct
{
  int A     : 16;
  Struct1 B;
} Struct2;

then

Struct2 abc;

abc.A = 0x1111;

abc.B.A = 0x1123;

abc.B.B = 0x3334;

accepts assignments and can be used like bitfields.

edited Jan 06 '15 at 03:19

answered Sep 28 '13 at 23:03

ryyker

22,849
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score 0 · Answer 2 · edited May 23 '17 at 10:25

0

This might be of assistance to you. Ofcourse you have to change the declarations a bit.

edited May 23 '17 at 10:25

Community

1
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answered Sep 28 '13 at 22:49

shunyo

1,277
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Thanks, Ryyker's comment seemed to do the trick! Just remove the bit-field declaration on Struct1, still needs some testing but we'll see. – Skynight Sep 28 '13 at 23:02

Bit-field struct within bit-field struct in C

2 Answers2