On 01/25/2012 12:09 AM, Peter Alexander wrote:
On Tuesday, 24 January 2012 at 22:26:37 UTC, Nick Sabalausky wrote:
This whole issue is literally *NO* different from "Should a public
pointer/reference be allowed to point to private data?" or "Should a
public function be allowed to expose a private one?" The answer is:
"Obviously yes".
Things can be obvious in different ways.
For example, one could argue that it's also obvious that an alias should
behave exactly the same as the thing it aliases. Allowing aliases to
change protection would break that.
The accessibility of something is not part of its behavior.
For the record, I agree that the answer should be "yes", but it's not a
decision that should be made rashly. If we aren't careful, we could
introduce a hole in the protection system in a non-obvious way. C++'s
protection system has a non-obvious hole:
http://bloglitb.blogspot.com/2010/07/access-to-private-members-thats-easy.html
Non-obvious? Perfectly obvious: Access checking rules do not apply to
names in explicit template instantiations. It is an explicit rule that
states access checking is subverted.
Again, I agree, but what's obvious isn't always true, so it needs to be
considered in depth.
Accessibility-raising aliases are trivially safe, because the alias
declaration must have access to the aliased symbol.
