[PATCH] Update the coding standards to provide some guidance for a few constructs in C++11

[Chandler Carruth]

On Tue, Mar 4, 2014 at 2:25 AM, Matt <matdzb at gmail.com> wrote:

> Hi!
>
> Out of curiosity, I'm wondering about the upsides/downsides of following
> the Scott Meyers' advice in this context.
> // "Develop the habit of using brace initialization without “=“.
> In: "Overview of the New C++ (C++11)"; http://www.aristeia.com/C++11.html
>
> In "Uniform Initialization Syntax" he provides an example where the
> alternative would fail:
> ```
> const float * pData = new const float[3] = { 1.f, 2.f, 3.f }; // error
> const float * pData = new const float[3] { 1.f, 2.f, 3.f }; // ok
> ```
>

The guidelines specifically recommend this type of thing -- here we have an
aggregate being initialized in the only way that makes sense.


>
> Similarly, another example shows that `T var = expr` syntax can’t call
> explicit constructors; adopting from the example (slightly simplifying,
> changing `Widget` to `struct`) therein:
>
> ```struct Widget
> {
>         explicit Widget(int);
> };
> Widget w1(10); // okay, direct init: explicit ctor callable
> Widget w2{10}; // ditto
> Widget w3 = 10; // error! copy init: explicit ctor not callable
> Widget w4 = {10}; // ditto```
>
> Or, is disallowing the above the actual intent?
>

Yes, disallowing this was the intent. If the constructor is 'explicit' then
this is not merely converting one value to another or doing something like
aggregate initialization. It is calling a very specific constructor
explicitly with a specific argument. That's what it says on the tin. I
would like for explicit calls to a specific constructor to look like
*calls* rather than like aggregate initialization, or worse, some strange
block scope. So instead, write 'Widget w1(10);' and everything is fine.

-Chandler
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