[dmd-beta] rvalue references

[Andrej Mitrovic]

On 4/12/12, Jonathan M Davis <jmdavisProg at gmx.com> wrote:
> Why do you need more than just normal pointers? Because of this proposal
> making taking the address of a ref illegal?

Yeah. For example:

extern(C) void c_modify_int(int* x) { }

void modify_int(ref int x)
{
    c_modify_int(&x);
}

void main()
{
    int x;
    modify_int(x);
}

Currently you don't have to use address-of operator if you mark the
extern(C) function as taking ref:

extern(C) void c_modify_int(ref int x) { }
void modify_int(ref int x)
{
    c_modify_int(x);
}

But if both of these get banned, the only way to pass by reference
while still keeping the same API would be to create a new temporary:

extern(C) void c_modify_int(int* x) { }
void modify_int(ref int x)
{
    int y = x;
    c_modify_int(&y);
    x = y;
}

Can this be optimized by the compiler? I don't know. It sure makes for
some ugly code, especially if the C function takes multiple pointer
arguments. I don't know how many libraries depend on working 'ref' on
C functions and/or taking address of a reference, but banning 'ref' on
C functions would break the existing wxD bindings.