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to size boundary of the structure alignment

Ras Sharif

dear All,

i started an arm cortex m3 project using eclipse+gnu.

i want to size boundary of the structure alignment.

where and how i can do it?

 

thanks and regards,

Ras

  • +1

    Hi Ras,

    it would be possible if the structure size is a positive power of 2.

    For example, the code

    struct struct1 {

     int i[10];// 40 bytes

     char c[24];// 24 bytes

    };

    struct struct1 __attribute__ ((aligned(sizeof(struct struct1)))) ic;

    int main()

    {

     ic.i[0]=0x12345678;

     ic.c[1]=0x5a;

     return 0;

    }

    would be compiled as the followings.

              .text
            .align  2
            .global main
            .thumb
            .thumb_func
            .type   main, %function
    main:
            ldr     r3, .L2
            ldr     r2, .L2+4
            str     r2, [r3]
            movs    r2, #90
            strb    r2, [r3, #41]
            movs    r0, #0
            bx      lr
    .L3:
            .align  2
    .L2:
            .word   ic
            .word   305419896
            .size   main, .-main
            .comm   ic,64,64

    Is this your intention?

    Best regards,

    Yasuhiko Koumoto.