How does a C-style struct with a bitfield get represented in a Rust #[repr(C)] struct?

by

No, you can’t.

There is an open issue about supporting bitfields, which doesn’t seem to be active. In the issue, @retep998 explains how bitfields are handled in winapi. That might be helpful if you need to handle bitfields in C interface.

OP seems to aim at C interoperation, but if you just need bitfields functionality, there are several solutions.

  • You should always consider simple redundant solution: avoid bitfields and let fields align naturally.
  • bitfield, according to the comment — I didn’t know that, but it seems to provide C bitfields equivalent.
  • bitflags. This seems suitable for bit-based flags, which typically represented as enum in C.
  • #[repr(packed)] if you just want to pack fields to some degree, ignoring alignment. The fields will still be aligned to byte boundary.
  • bit-vec if you need homogenious arrays of bits.

More Related Contents:

  1. "." or "->" C struct accessor [duplicate]
  2. free() not working correctly with struct
  3. C expected expression before struct error
  4. Reading and analyzing rooms from text file
  5. Struct memory layout in C
  6. Why bit endianness is an issue in bitfields?
  7. How do you compare structs for equality in C?
  8. How do I check if a variable is of a certain type (compare two types) in C?
  9. Initialize/reset struct to zero/null
  10. Casting one struct pointer to another – C
  11. Why doesn’t GCC optimize structs?
  12. How to initialize const in a struct in C (with malloc)
  13. C Typedef and Struct Question
  14. Writing a ‘generic’ struct-print method in C
  15. Trouble Understanding MPI_Type_create_struct
  16. Can we have a struct element of type Variable length array? [duplicate]
  17. Empty structure in C
  18. what is the difference between struct {0} and memset 0 [duplicate]
  19. Array of variable length in a structure
  20. forward declaration of a struct in C?
  21. Is there any way to loop through a struct with elements of different types in C?
  22. Access struct members as if they are a single array?
  23. Flexible array member not getting copied when I make a shallow copy of a struct
  24. size of struct in C [duplicate]
  25. Does GCC’s __attribute__((__packed__)) retain the original ordering?
  26. How do you use offsetof() on a struct?
  27. Returning a struct pointer
  28. Why does static initialization of flexible array member work?
  29. Questions about C bitfields
  30. Signed bit field represetation

Leave a Comment