[Interest] QFlags: Typesafe way to check "any flag set"

[Giuseppe D'Angelo]

On 18/02/2026 13:00, Schimkowitsch Robert wrote:
> When I look at qflags.h in 6.10.2, I notice that there is
> 
> constexpr inline bool operator!() const noexcept { return !i; }
> 
> …but operator bool() is listed in the non-TYPESAFE section.
> 
> Does this mean that if I want to check if any flag is set, I need to do 
> this?
> 
> // Check if any flag is set
> 
> if ( !! flags)
> 
> { /* do something */ }
> 

Are you looking at

> #ifdef QT_TYPESAFE_FLAGS
>     constexpr inline explicit operator Int() const noexcept { return i; }
>     constexpr inline explicit operator bool() const noexcept { return i; }
> #else
>     constexpr inline Q_IMPLICIT operator Int() const noexcept { return i; }
>     constexpr inline bool operator!() const noexcept { return !i; }
> #endif

?

In the else branch (non-typesafe) there's an implicit operator int(), so 
you can just write if (flags) or if (flags != 0). 
https://gcc.godbolt.org/z/zebhah5cr

Note that QT_TYPESAFE_FLAGS is a Qt-internal feature at the moment, and 
not enabled for user code. (Qt itself isn't clean, only QtCore builds 
with it.)

HTH,
-- 
Giuseppe D'Angelo | giuseppe.dangelo at kdab.com | Senior Software Engineer
KDAB (France) S.A.S., a KDAB Group company
Tel. France +33 (0)4 90 84 08 53, http://www.kdab.com
KDAB - Trusted Software Excellence
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