Rvalue references - The resolution

[Michel Fortin]

On 2013-05-04 18:33:10 +0000, Walter Bright <newshound2 at digitalmars.com> said:

> Runtime Detection
> 
> There are still a few cases that the compiler cannot statically detect. 
> For these a runtime check is inserted, which compares the returned ref 
> pointer to see if it lies within the stack frame of the exiting 
> function, and if it does, halts the program. The cost will be a couple 
> of CMP instructions and an LEA. These checks would be omitted if the 
> -noboundscheck compiler switch was provided.

I just want to note that this has the effect of making any kind of heap 
allocation not done by the GC unsafe. For instance, if you have a 
container struct that allocates using malloc/realloc and that container 
gives access to its elements by reference then you're screwed (it can't 
be detected).

The obvious answer is to not make @trusted the function returning a 
reference or a slice to malloced memory. But I remember Andrei wanting 
to make standard containers of this sort at one point, so I think it's 
important to note this limitation.

-- 
Michel Fortin
michel.fortin at michelf.ca
http://michelf.ca/