Use the following class to help calculate the alignment in C++:
template<typename T>class Alignment{ struct Align { char align; T t; };public: int alignment() { return sizeof(Align) - sizeof(T); }};Below are two examples that use the Alignment class. The first one is for the char data type; the second one is for the iostream class from the standard Input/Output streams library:
Alignment char_type; std::cout << char_type.alignment() << std::endl; Alignment The alignment requirement for a data object is hardware- and compiler-specific parameter. Even on the same machine and with the same compiler, the alignment for the same type can be different depending on compiler-specific options. For example, the following compiler command:
#pragma pack(2)will result in many compilers to use at most two-byte alignment for the data that follow the directive (please note that pragma directives cannot increase alignment for a data object).
