Soren Holstebroe wrote:

An important feature of the fixed point template is that it takes up no more space than the underlying integer. It should be possible to use reinterpret_cast to convert a third party integer pointer (representing fixed ints) to a fixed point template pointer.

The way I ensure that in my fixed point template is with a #pragma: #pragma pack(push, 1) ... template struct ... #pragma pack(pop)

This is supported by MSVC++ as well as gcc. However it is only defacto standard, so it might not work on any other compiler.

Is there a more standard way to make sure that the struct is not padded to some memory alignment size?

assert(sizeof(fixed<N>)==expected_size) - and let the user worry about what they need to add if the assertion fails. In my (limited) experience, the only place where this would be a problem is on the old ARM ABI where struct alignment is normally always at least 4 bytes even if the struct only contains one byte. gcc's __attribute__((packed)) fixes that. Phil.