[cfe-dev] [libcxx] std::atomic default constructor

Howard Hinnant hhinnant at apple.com
Fri Mar 15 13:34:50 PDT 2013

Looks like a bug that needs fixing.  When I wrote <atomic>, = default wasn't implemented yet.  The entire library needs to be scanned for this issue.  And the fix needs to be macro'd up so that we don't break C++03 mode more than it already is.


On Mar 15, 2013, at 3:50 PM, Stephan Tolksdorf <st at quanttec.com> wrote:

> Hi,
> Is there a reason that the default constructors for the std::atomic types in libc++'s <atomic> are not explicitly defaulted? In the header the "= default" is commented out and instead a trivial constructor is explicitly defined. This leads to non-standard behaviour, because value initialization doesn't zero-initialize the atomic value.
> For example, the default constructor of the following struct Test does not zero-initialize atomicValue as expected:
> struct Test {
>    int value{}; // is zero-initialized
>    std::atomic<int> atomicValue{}; // is not zero-initialized
> };
> Best regards,
>  Stephan
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