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cstructalignment

C struct aligned

Is there some gcc portable pragma, so I can do C struct not to be memory aligned?

I want my program to be portable (Linux, FreeBSD, MacOS, Cygwin), but I will stay with gcc.

Solution

  • If you don't want to align members of a structure (that is not have any padding between members), with gcc you can use packed attribute:

    struct bla
{
    int x;
    char y;
} __attribute__((__packed__));

    or use pack pragma:

    #pragma pack(1)
struct bla
{
     int x;
     char y;
};
#pragma pack()

    or compile using -fpack-struct option.

    You can also force a minimum alignment for the whole structure with aligned attribute, but as far as I know you cannot disable the alignment of the whole structure with gcc.