Struct byte alignment (excluding discussion about struct nesting and modifying the alignment of machines). For more details, see add to favorites.

Byte alignment:

1. The offset from the first address must be an integer multiple of the variable length.

2. the variables are stored in the defined order.

3. The length of the entire struct must be an integer multiple of the length of the longest member variable.

4 If struct is nested, the variables in the sub-struct must comply with the preceding three principles throughout the entire struct, but the storage location of each variable in the sub-struct itself will not change.

E.g.

Struct nssb {
Long;
Short B;
Char C;
Short D;
Char ch [3];
} OBJ, * P;

Cout <"sizeof long" <sizeof (long) <Endl;
Cout <"sizeof double" <sizeof (double) <Endl;
Cout <"sizeof float" <sizeof (float) <Endl;
Cout <"sizeof int" <sizeof (INT) <Endl;
Cout <"sizeof short" <sizeof (short) <Endl;
Cout <"sizeof char" <sizeof (char) <Endl;
Cout <"sizeof P" <sizeof (p) <Endl;
Cout <"sizeof * P" <sizeof (* P) <Endl;

P = (struct nssb x *) 0x1000000;
// Cout <"next struct is" <(p + 0x1) <Endl;
// Obj. c = 'C ';
Cout <"A" <& obj. A <Endl;
Cout <"B" <& obj. B <Endl;
Cout <"C" <& obj. C <Endl;
Cout <"D" <& obj. d <Endl;
Cout <"ch" <& obj. ch <Endl;

 

Running result:

[Root @ 127 test] #./test. x
Sizeof long 4
Sizeof double 8
Sizeof float 4
Sizeof int 4
Sizeof short 2
Sizeof char 1
Sizeof P 4
Sizeof * P 16
A 0xbfcee3c0
B 0xbfcee3c4
C d.
D 0xbfcee3c8
Ch 0xbfcee3ca