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Controls how the members of a structure are packed into memory and specifies the same packing for all structures in a module.
/Zp[1|2|4|8|16]
The /ZpN option tells the compiler where to store each structure member. The compiler stores members after the first one on a boundary that's the smaller of either the size of the member type, or an N-byte boundary.
The available packing values are described in the following table:
| /Zp argument | Effect |
|---|---|
| 1 | Packs structures on 1-byte boundaries. Same as /Zp. |
| 2 | Packs structures on 2-byte boundaries. |
| 4 | Packs structures on 4-byte boundaries. |
| 8 | Packs structures on 8-byte boundaries (default for x86, ARM, and ARM64). |
| 16 | Packs structures on 16-byte boundaries (default for x64 and ARM64EC). |
Don't use this option unless you have specific alignment requirements.
Warning
The C/C++ headers in the Windows SDK assume the platform's default alignment is used. Don't change the setting from the default when you include the Windows SDK headers, either by using /Zp on the command line or by using #pragma pack. Otherwise, your application may cause memory corruption at runtime.
You can also use the pack pragma to control structure packing. For more information about alignment, see:
Open the project's Property Pages dialog box. For details, see Set C++ compiler and build properties in Visual Studio.
Select the Configuration Properties > C/C++ > Code Generation property page.
Modify the Struct Member Alignment property.