c++ - std::tuple memory alignment

Question

Is there any formal specification for the layout and memory alignment for the pseudo members of a tuple?

Is there anyway to modify the memory alignment of types in a tuple? Is it effected by a #pragma pack() directive?

For example:

typedef std::tuple<uint8_t, uint32_t> myTuple;

Is there any specification that says this will be in memory the same as:

#pragma pack() // Default packing
struct myStruct
{
    uint8_t first;
    uint32_t second;
}

Apologies if this is a stupid question but I don't entirely understand alignment when it comes to templates.

Edit: Example of what I'm trying to accomplish

Currently I have something along the lines of...

#pragma pack(push)
#pragma pack(4)
struct cTriangle
{
    uint32 Index[3];
};
#pragma pack(pop)

template <class T>
inline bool Read(cFileStream& fStream, std::vector<T>& vec)
{
    if (!vec.size())
        return true;

    // fStream.Read(void* pBuffer, size_t Size)
    // Just a wrapper around a binary ifstream really
    return fStream.Read(&vec[0], sizeof(T) * vec.size());
}

std::vector<cVector3> vPoint;
vPoint.resize(Verticies);
bool result = Read(FileStream, vPoint);

If I wanted to typedef cTriangle as std::tuple<uint32, uint32, uint32> for metaprogramming purposes would I still be able to read/write to the raw memory of the tuple (and thus a vector of tuples) or would that memory have unknown alignment?

Answer 1

Not only is there no requirement that the objects be arranged any particular way, but many tuple implementations actually put the second object before the first one.