| title | Examples of Structure Alignment | Microsoft Docs | ||
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| ms.date | 03/26/2018 | ||
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| ms.topic | conceptual | ||
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| ms.assetid | 03d137bf-5cc4-472e-9583-6498f2534199 | ||
| author | corob-msft | ||
| ms.author | corob | ||
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The following four examples each declare an aligned structure or union, and the corresponding figures illustrate the layout of that structure or union in memory. Each column in a figure represents a byte of memory, and the number in the column indicates the displacement of that byte. The name in the second row of each figure corresponds to the name of a variable in the declaration. The shaded columns indicate padding that is required to achieve the specified alignment.
// Total size = 2 bytes, alignment = 2 bytes (word).
_declspec(align(2)) struct {
short a; // +0; size = 2 bytes
}
// Total size = 24 bytes, alignment = 8 bytes (quadword).
_declspec(align(8)) struct {
int a; // +0; size = 4 bytes
double b; // +8; size = 8 bytes
short c; // +16; size = 2 bytes
}
// Total size = 22 bytes, alignment = 4 bytes (doubleword).
_declspec(align(4)) struct {
char a; // +0; size = 1 byte
short b; // +2; size = 2 bytes
char c; // +4; size = 1 byte
int d; // +8; size = 4 bytes
}
// Total size = 8 bytes, alignment = 8 bytes (quadword).
_declspec(align(8)) union {
char *p; // +0; size = 8 bytes
short s; // +0; size = 2 bytes
long l; // +0; size = 4 bytes
}