[LLVMdev] New type of smart pointer for LLVM (original) (raw)

Chandler Carruth chandlerc at google.com
Wed Oct 1 15:53:58 PDT 2014

On Wed, Oct 1, 2014 at 3:36 PM, David Blaikie <dblaikie at gmail.com> wrote:

On Wed, Oct 1, 2014 at 3:14 PM, Anton Yartsev <anton.yartsev at gmail.com> wrote:

Ping!

Suggested is a wrapper over a raw pointer that is intended for freeing wrapped memory at the end of wrappers lifetime if ownership of a raw pointer was not taken away during the lifetime of the wrapper. The main difference from uniqueptr is an ability to access the wrapped pointer after the ownership is transferred. To make the ownership clearer the wrapper is designed for local-scope usage only. I'm still concerned this isn't the right direction, and that we instead want a more formal "maybe owning pointer". The specific use case you've designed for here, in my experience, doesn't seem to come up often enough to justify a custom ADT - but the more general tool of sometimes-owning smart pointer seems common enough (& problematic enough) to warrant a generic data structure (and such a structure would also be appliable to the TGParser use case where this came up). I'd love to hear some more opinions, but maybe we're not going to get them...

I strongly agree that the example here isn't compelling.

I think it is a very fundamental design problem when there is a need for a pointer value after it has been deallocated...

I even question whether we need a "maybe owning" smart pointer, or whether this is just an indication that the underlying data structure is wrong. The idea of "maybe" and "owning" going to gether, in any sense, seems flat out broken to me from a design perspective, and so I'm not enthused about providing abstractions that make it easier to build systems with unclear ownership semantics. -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.llvm.org/pipermail/llvm-dev/attachments/20141001/307211fb/attachment.html>

More information about the llvm-dev mailing list