[libcxx] r185265 - Add operators to make launch a bitmask type. Searched all of the standard, and libc++ to see if this error occurred elsewhere and didn't see any other place. This fixes http://llvm.org/bugs/show_bug.cgi?id=16207

Marshall Clow mclow.lists at gmail.com
Mon Jul 1 06:15:46 PDT 2013

On Jun 29, 2013, at 11:38 AM, Howard Hinnant <hhinnant at apple.com> wrote:

> +launch
> +operator~(launch __x)
> +{
> +    return static_cast<launch>(~static_cast<__launch_underlying_type>(__x));
> +}

This may cause problems down the line, because it sets bits in launch that are not defined to have any meaning.
I ran into this kind of stuff when trying to use UBSan.

To prevent this problem, you can AND the result with 3, clearing all the unused bits.

> +    return static_cast<launch>(~static_cast<__launch_underlying_type>(__x) & 3);

(Yeah, I hate the naked '3' there too.)

-- Marshall

Marshall Clow     Idio Software   <mailto:mclow.lists at gmail.com>

A.D. 1517: Martin Luther nails his 95 Theses to the church door and is promptly moderated down to (-1, Flamebait).
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