Re: [boost] Heads up - string_ref landing

Subject: Re: [boost] Heads up - string_ref landing
From: Yanchenko Maxim (maximyanchenko_at_[hidden])
Date: 2012-11-26 22:03:28

26.11.12, 20:54, "Daniel James" <dnljms_at_[hidden]>":
> 
> On 26 November 2012 11:56, Andrey Semashev <andrey.semashev_at_[hidden]> wrote:
> > The problem with std::string is the same as with string_ref - it
> > doesn't support implicit construction from an arbitrary range, so my
> > examples with custom string types would still not work.
> 
> Shouldn't construction from an arbitrary range be explicit? Arbitrary
> implicit conversions are problematic. To get implicit construction
> from third party strings, I'd use some sort of explicit customisation
> mechanism.

Hi Daniel, I'm fully with you here. The construction of string_ref should be explicit (except maybe literals if we can detect them in compile time) as we're giving away pointers to something that is externally managed. 
Look at std::string::c_str/data, any smart_ptr::get etc - everything is explicit for a reason. Implicit conversions to pointers are very dangerous here. 
No containers give away their internals implicitly, and this is Good Thing. 

Consider a vector of pointers, for example. You don't want to implicitly put a pointer managed by a smart pointer there, you want it to be explicit so it's visible and you don't forget putting reset/release near a push_back. Same applies to a vector of string_ref - you want to be sure that the string referred by it lives as long a needed, and there is no other way except explicit construction. 

Thanks, 
Maxim