About union

[EricLi]

*typedef struct ct_data_s {
union {
long freq; /* frequency count */
long code; /* bit string */
} fc;
union {
char dad; /* father node in Huffman tree */
char len; /* length of bit string */
} dl;
} ct_data;

void main( )
{
int i = sizeof( ct_data );
}*


why does i equal 8?
I think the result is 5(sizeof(long)+sizeof(char))


-
EricL

 

[Kenneth Brody]

*typedef struct ct_data_s {
union {
long freq; /* frequency count */
long code; /* bit string */
} fc;
union {
char dad; /* father node in Huffman tree */
char len; /* length of bit string */
} dl;
} ct_data;

void main( )
{
int i = sizeof( ct_data );
}*

why does i equal 8?
I think the result is 5(sizeof(long)+sizeof(char)).

Because, on your platform, longs must be aligned on a 4-byte boundary.
Therefore, if you were to make an array of ct_data elements, the second
element would have to be aligned at offset 8. Therefore, sizeof(ct_data)
must be 8.

 

[Martin Ambuhl]

*typedef struct ct_data_s {
union {
long freq; /* frequency count */
long code; /* bit string */
} fc;
union {
char dad; /* father node in Huffman tree */
char len; /* length of bit string */
} dl;
} ct_data;

void main( )

^^^^^^
After this illiteracy, no one can say what your program should do.

{
int i = sizeof( ct_data );
}*


why does i equal 8?

It could have been 42.

I think the result is 5(sizeof(long)+sizeof(char)).

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