Hi David,

This doesn't sound like an editorial issue. It's probably a CWG issue - you can check the CWG active issues list or Richard might chime in here.

Thanks,

Stefanus

—
Stefanus Du Toit

On Thu, Nov 21, 2013 at 4:09 AM, David Krauss notifications@github.com
wrote:

DefaultConstructible requires T x(), T x{}, T() and T{} be valid statements but says nothing about T x = {} , a.k.a. copy-list-initialization. This is the semantic used to initialize a function parameter from an empty list argument.
Copy-list-initialization will not call an explicit constructor (13.3.1.7 [over.match.list]), which is not otherwise required by DefaultConstructible. The standard containers have such explicit default constructors (specifically, would-be conversion constructors with default argument).
Therefore, this is invalid:
void f( std::vector< int > ) {}
f( {} );
As far as I've seen, only GCC 4.9 rejects this; Clang and GCC up to 4.8 accept it.

The specific problem with containers as illustrated may be considered a separate defect.

Reply to this email directly or view it on GitHub:
#236

There's a library issue opened by Richard to make the container default constructors non-explicit, and I'm going to fix gcc 4.9 so the constructors are not explicit. They never should have been explicit and gcc should not have changed them.

http://cplusplus.github.io/LWG/lwg-active.html#2193 is the issue I was referring to.