A simple in-place swap macro for C

swap.c

#define swap(a, b) do {\
    typedef struct { char data[sizeof(a) == sizeof(b) ? sizeof(a) : -1]; } swap;\
    swap* const aa = (swap*)&(a);\
    swap* const bb = (swap*)&(b);\
    swap  const cc = *aa; *aa = *bb; *bb = cc;\
} while(0)