portable way to pack structures

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  • portable way to pack structures

    Hi,

    Currently, i’m using the Keil-MDK IDE for my projects and i like to use the embedded studio to test my codes with GCC and/or LLVM.
    Unfortunately, i need packed structures for the communication with other system. I#m using the ARM Compiler Keyword packed for this.

    What would be the right way to declare these structures compiler independent?

    For example:

    C Source Code

    1. typedef __packed struct
    2. {
    3. __packed union
    4. {
    5. __packed struct
    6. {
    7. uint32_t component : 4;
    8. uint32_t unused : 12;
    9. uint32_t size : 11;
    10. uint32_t Flag : 1;
    11. uint32_t typ : 4;
    12. } Header;
    13. unsigned long Header32;
    14. } pkt;
    15. uint32_t infol[INFOSIZE];
    17. __packed union
    18. {
    19. __packed struct
    20. {
    21. uint32_t Data : 16;
    22. uint32_t subdata : 7;
    23. uint32_t busy : 1;
    24. uint32_t Addr : 4;
    25. uint32_t Cmd : 4;
    26. } cmdpkt;
    27. uint32_t Cmd32;
    28. } Cmd[31];
    29. } xyz_TypeDef;
    Display All


    Thank you
    Martin

  • For GCC/LLVM you need to set the attribute packed to the struct or union.
    struct __attribute__ ((__packed__)) my_packed_struct

    To make it compiler independent you would need to wrap this with pre-processor macros based on the toolchain defines.

    Regards
    Johannes
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