| Message ID | 20220405004215.86340-4-Rauch.Christian@gmx.de |
|---|---|
| State | Superseded |
| Headers | show |
| Series |
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| Related | show |
Hi Christian, Thank you for the patch. On Tue, Apr 05, 2022 at 01:42:13AM +0100, Christian Rauch via libcamera-devel wrote: > This allows to construct empty 0-fixed-sized Spans. > > Signed-off-by: Christian Rauch <Rauch.Christian@gmx.de> > --- > include/libcamera/base/span.h | 2 -- > include/libcamera/controls.h | 2 +- > 2 files changed, 1 insertion(+), 3 deletions(-) > > diff --git a/include/libcamera/base/span.h b/include/libcamera/base/span.h > index 88d2e3de..bff4c115 100644 > --- a/include/libcamera/base/span.h > +++ b/include/libcamera/base/span.h > @@ -105,8 +105,6 @@ public: > > static constexpr std::size_t extent = Extent; > > - template<bool Dependent = false, > - typename = std::enable_if_t<Dependent || Extent == 0>> The issue here is that the std::span class has this constraint ([1]): This overload participates in overload resolution only if extent == 0 || extent == std::dynamic_extent. [1] https://en.cppreference.com/w/cpp/container/span/span If we drop the constraint here, we will have an issue when switching to std::span in the future. Is there a way we could achieve the result you're aiming for without this change ? > constexpr Span() noexcept > : data_(nullptr) > { > diff --git a/include/libcamera/controls.h b/include/libcamera/controls.h > index 665bcac1..de8a7770 100644 > --- a/include/libcamera/controls.h > +++ b/include/libcamera/controls.h > @@ -167,7 +167,7 @@ public: > > using V = typename T::value_type; > const V *value = reinterpret_cast<const V *>(data().data()); > - return { value, numElements_ }; > + return T{ value, numElements_ }; > } > > #ifndef __DOXYGEN__
Hi Laurent, If we can only default-construct a Span that is either 0-fixed-sized or variable-sized, and we want to return default-constructed objects to indicate errors, then it is not possible to use N-fixed-size Spans. We either have to use a Span type that supports N-fixed-sized default-construction, or the default-construction of types has to be avoided. If having feature/behaviour comparability with std::span is a high priority, then only the option that avoids default-construction is left. Best, Christian Am 05.04.22 um 17:27 schrieb Laurent Pinchart: > Hi Christian, > > Thank you for the patch. > > On Tue, Apr 05, 2022 at 01:42:13AM +0100, Christian Rauch via libcamera-devel wrote: >> This allows to construct empty 0-fixed-sized Spans. >> >> Signed-off-by: Christian Rauch <Rauch.Christian@gmx.de> >> --- >> include/libcamera/base/span.h | 2 -- >> include/libcamera/controls.h | 2 +- >> 2 files changed, 1 insertion(+), 3 deletions(-) >> >> diff --git a/include/libcamera/base/span.h b/include/libcamera/base/span.h >> index 88d2e3de..bff4c115 100644 >> --- a/include/libcamera/base/span.h >> +++ b/include/libcamera/base/span.h >> @@ -105,8 +105,6 @@ public: >> >> static constexpr std::size_t extent = Extent; >> >> - template<bool Dependent = false, >> - typename = std::enable_if_t<Dependent || Extent == 0>> > > The issue here is that the std::span class has this constraint ([1]): > > This overload participates in overload resolution only if > extent == 0 || extent == std::dynamic_extent. > > [1] https://en.cppreference.com/w/cpp/container/span/span > > If we drop the constraint here, we will have an issue when switching to > std::span in the future. Is there a way we could achieve the result > you're aiming for without this change ? > >> constexpr Span() noexcept >> : data_(nullptr) >> { >> diff --git a/include/libcamera/controls.h b/include/libcamera/controls.h >> index 665bcac1..de8a7770 100644 >> --- a/include/libcamera/controls.h >> +++ b/include/libcamera/controls.h >> @@ -167,7 +167,7 @@ public: >> >> using V = typename T::value_type; >> const V *value = reinterpret_cast<const V *>(data().data()); >> - return { value, numElements_ }; >> + return T{ value, numElements_ }; >> } >> >> #ifndef __DOXYGEN__ >
diff --git a/include/libcamera/base/span.h b/include/libcamera/base/span.h index 88d2e3de..bff4c115 100644 --- a/include/libcamera/base/span.h +++ b/include/libcamera/base/span.h @@ -105,8 +105,6 @@ public: static constexpr std::size_t extent = Extent; - template<bool Dependent = false, - typename = std::enable_if_t<Dependent || Extent == 0>> constexpr Span() noexcept : data_(nullptr) { diff --git a/include/libcamera/controls.h b/include/libcamera/controls.h index 665bcac1..de8a7770 100644 --- a/include/libcamera/controls.h +++ b/include/libcamera/controls.h @@ -167,7 +167,7 @@ public: using V = typename T::value_type; const V *value = reinterpret_cast<const V *>(data().data()); - return { value, numElements_ }; + return T{ value, numElements_ }; } #ifndef __DOXYGEN__
This allows to construct empty 0-fixed-sized Spans. Signed-off-by: Christian Rauch <Rauch.Christian@gmx.de> --- include/libcamera/base/span.h | 2 -- include/libcamera/controls.h | 2 +- 2 files changed, 1 insertion(+), 3 deletions(-) -- 2.25.1