Re: [boost] [serialization] Passing literals to oarchive

Subject: Re: [boost] [serialization] Passing literals to oarchive
From: Gavin Lambert (gavinl_at_[hidden])
Date: 2015-03-30 01:02:56

On 30/03/2015 04:35, Robert Ramey wrote:
> Bjorn Reese wrote
>> On 03/27/2015 05:49 PM, Robert Ramey wrote:
>>
>>> In this case the problem is different.  A parameter value placed on the
>>> stack cannot be passed by "const T & t".  This syntax assumes and
>>> enforces
>>
>> Why not?
>
> It generates a compile time error when you pass an rvalue.

It shouldn't.  Literals are definitely compatible with "const T &".

I'm not 100% certain but I believe rvalue references "T&&" should also 
be compatible, although they will probably collapse to basic references.

> the reason I would think that it's not a common case is the following:
>
> ar << 42;  // put the value of 42 into the archive
> ...
>
> ar >> ?;  // what do we do with the result we're retrieving?
>
> So I'm not seeing where this comes up.

Obviously >> must have an lvalue.  That doesn't constrain << though.

The OP was referring to unit tests, where presumably they were wanting 
to poke raw values into an archive in a particular order and verify that 
they deserialised the correct way into an actual object.

As for why they wanted to do that, I don't know, but I can guess that 
one possibility is for testing backwards compatibility: given a known 
sequence of values written by some prior version of the object, verify 
that it deserialises correctly in the current version of the object. 
But there's lots of other possibilities too.