For example, an 8-byte floating-point datum is naturally aligned if the address used to identify it has an 8-byte alignment. We call a datum naturally aligned if its address is aligned to its size. The data are identified by their addresses in memory. An address is said to be aligned to X if its alignment is Xn+0.ĬPUs execute instructions that operate on data stored in memory. The alignment of an address depends on the chosen power of 2.
![wordfast memory alignment wordfast memory alignment](https://localizationlocalisation.files.wordpress.com/2013/04/wordfast-install-wizard-component-selection.png)
That address is said to be aligned to 4n+3, where 4 indicates the chosen power of 2. For example, the address 0x0001103F modulo 4 is 3. Alignment and memory addressesĪlignment is a property of a memory address, expressed as the numeric address modulo a power of 2. The aligned_union class is for specifying alignment for unions with non-trivial constructors or destructors. Use the aligned_storage class for memory allocation of data structures with custom alignments. The C++ standard doesn't specify packing behavior for alignment on boundaries smaller than the compiler default for the target platform, so you still need to use the Microsoft #pragma pack in that case. For more information, see alignof Operator and align. The documentation for those extensions also applies to the new keywords. The new keywords behave in the same way under the hood as the Microsoft-specific extensions.
Wordfast memory alignment code#
Starting in Visual Studio 2015 you should use the C++11 standard keywords alignof and alignas for maximum code portability.
![wordfast memory alignment wordfast memory alignment](https://www.memoq.com/wp-content/uploads/2019/02/memoq.png)
Before Visual Studio 2015 you could use the Microsoft-specific keywords _alignof and _declspec(align) to specify an alignment greater than the default. In some cases, however, you can achieve significant performance improvements, or memory savings, by specifying a custom alignment for your data structures. In most scenarios, you never have to be concerned with alignment because the default alignment is already optimal. By default, the compiler aligns class and struct members on their size value: bool and char on 1-byte boundaries, short on 2-byte boundaries, int, long, and float on 4-byte boundaries, and long long, double, and long double on 8-byte boundaries. One of the low-level features of C++ is the ability to specify the precise alignment of objects in memory to take maximum advantage of a specific hardware architecture.