[PATCH] SemaDeclCXX.cpp: Make -Wglobal-constructors more forgiving.

[Yury Gribov]

On 01/23/2015 11:03 AM, David Blaikie wrote:
> On Thu, Jan 22, 2015 at 10:43 PM, Yury Gribov <y.gribov at samsung.com> wrote:
>
>> On 01/22/2015 08:39 PM, David Blaikie wrote:
>>
>>> On Thu, Jan 22, 2015 at 1:38 AM, Yury Gribov <tetra2005 at gmail.com> wrote:
>>>
>>>   Hi rsmith, eli.friedman,
>>>>
>>>> This patch liberalizes -Wglobal-constructors to not emit warning if
>>>> constructor is likely to be optimized away. This covers important
>>>> LinkerInitialized idiom used e.g. in libsanitizer and Chromium:
>>>>     enum LinkerInitialized { LINKER_INITIALIZED };
>>>>     class Mutex {
>>>>     public:
>>>>       inline Mutex(base::LinkerInitialized) {}
>>>>     };
>>>>     Mutex mu(LINKER_INITIALIZED);  // Will be optimized away
>>>>
>>>>
>>> While this is probably a useful improvement to C++98 code, is there any
>>> reason this code couldn't use C++11's constexpr instead? (which I think
>>> would already not produce the warning without needing to change the
>>> compiler)
>>>
>>
>> Constexpr would work in simple cases but will fail if class includes an
>> array (for-loops are prohibited in constexpr but all members have to be
>> initialized).
>
>
> Got an example of this? I'd imagine an in-class initializer might suffice
> for the array. ( int x[3] = {}; ) ?

Yup, this seems to do the trick. I guess the patch is thus not that 
important.

-Y