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Array doubles in size if a struct defines both its uint16_t words and uint8_t bytes


Instead of an array of 2 bytes, use a structure of 2 bytes:

// Two bytes in a 16-bit word
typedef struct{
    uint8_t     lsb;    // As uint8_t, LSB
    uint8_t     msb;    // As uint8_t. MSB
} two_bytes_t;

typedef union {
   uint16_t u16;   // As uint16_t
   two_bytes_t  u8x2; // As 2 each of uint8_t
} my_array_t;


my_array_t my_array[1]; // 1 word array, for
testing

my_array[0].u8x2.msb = 1;
my_array[0].u8x2.lsb = 2;

The XC16 compiler correctly allocates only 2 bytes for each element, and the debugger correctly shows the individual bytes.


Categories : C

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