On Fri, 08 Oct 2010 09:33:22 +0200, Benjamin Thaut wrote:
Hi, I'm writing a vec4 math struct and I have a method of which the
return value has to be a lvalue so I wonder which is the correct way
to do this:
vec4 Normalize() const { ... } //won't work, not a lvalue
ref vec4 Normalize() const {
vec4 temp;
...
return temp;
} //will this lead to a segfault or not?
The compiler shouldn't even accept this. When I try a similar thing,
DMD says "Error: escaping reference to local variable temp".
ref vec4 Normalize() const {
vec4* temp = new vec4;
...
return *temp;
} //ugly, don't want to allocate anything on the heap
This would work, since the variable is no longer on the stack and
thus survives the return of the function.
auto ref vec4 Normalize() const {
vec4 temp;
...
return temp;
} //will this lead to a segfault?
Well, that should compile, but it doesn't work the way you want.
'auto ref' means that the function returns by ref if the return
expression is an lvalue *and it would not be a reference to a local
or a parameter*. So for this example, your function would return by
value, not by ref.
Or do I need to do it totaly in some other way?
Yes, you do. :) You are trying to create a variable on the stack,
and return it by reference. The problem is that when the function
returns, its stack frame (the memory occupied by the function's local
variables) is "released". At that point the variable doesn't exist
anymore, and any reference to it would be invalid.
-Lars
