4a7aae86f9
Although `vtkm::internal::Variant` respected the trivially copyable attribute of the types it contains, it was never totally trivial (i.e. `std::is_trivial<Variant<...>>` was never true). The reason was that `Variant` was initializing its `Index` parameter to signify that it was not initialized. However, the fact that `Index` was initialized meant that it was not trivially constructed. Now, `Variant` type checks its types to see if they are all trivially constructible. If so, it makes itself trivially constructible. This means that `Index` may or may not be valid if `Variant` is constructed without an argument. This in turn means that the result of `Variant::IsValid` becomes undefined. That should be OK in practice. `Index` will "point" to an uninitialized object, but that object is trivially constructed anyway. However, that could cause problems if developers used `IsValid` to determine if something is selected.
86 lines
3.4 KiB
C++
86 lines
3.4 KiB
C++
//============================================================================
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// Copyright (c) Kitware, Inc.
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// All rights reserved.
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// See LICENSE.txt for details.
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//
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// This software is distributed WITHOUT ANY WARRANTY; without even
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// the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR
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// PURPOSE. See the above copyright notice for more information.
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//============================================================================
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#ifndef vtk_m_std_is_trivial_h
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#define vtk_m_std_is_trivial_h
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#include <vtkm/StaticAssert.h>
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#include <type_traits>
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#if defined(VTKM_USING_GLIBCXX_4)
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namespace vtkmstd
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{
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// GCC 4.8 and 4.9 standard library does not support std::is_trivially_copyable.
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// There is no relyable way to get this information (since it has to come special from
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// the compiler). For our purposes, we will report as nothing being trivially copyable,
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// which causes us to call the constructors with everything. This should be fine unless
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// some other part of the compiler is trying to check for trivial copies (perhaps nvcc
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// on top of GCC 4.8).
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template <typename>
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struct is_trivially_copyable : std::false_type
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{
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};
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// I haven't tried the other forms of is_trivial, but let's just assume they don't
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// work as expected.
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template <typename...>
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struct is_trivially_constructible : std::false_type
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{
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};
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template <typename>
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struct is_trivially_destructible : std::false_type
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{
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};
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template <typename>
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struct is_trivial : std::false_type
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{
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};
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// A common exception to reporting nothing as trivially copyable is assertions that
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// a class is trivially copyable. If we have code that _only_ works with trivially
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// copyable classes, we don't want to report nothing as trivially copyably, because
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// that will error out for everything. For this case, we define the macro
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// `VTKM_IS_TRIVIALLY_COPYABLE`, which will always pass on compilers that don't
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// support is_trivially_copyable, but will do the correct check on compilers that
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// do support it.
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#define VTKM_IS_TRIVIALLY_COPYABLE(type) VTKM_STATIC_ASSERT(true)
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#define VTKM_IS_TRIVIALLY_CONSTRUCTIBLE(...) VTKM_STATIC_ASSERT(true)
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#define VTKM_IS_TRIVIALLY_DESTRUCTIBLE(...) VTKM_STATIC_ASSERT(true)
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#define VTKM_IS_TRIVIAL(type) VTKM_STATIC_ASSERT(true)
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} // namespace vtkmstd
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#else // NOT VTKM_USING_GLIBCXX_4
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namespace vtkmstd
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{
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using std::is_trivial;
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using std::is_trivially_constructible;
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using std::is_trivially_copyable;
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using std::is_trivially_destructible;
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#define VTKM_IS_TRIVIALLY_COPYABLE(type) \
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VTKM_STATIC_ASSERT_MSG(::vtkmstd::is_trivially_copyable<type>::value, \
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"Type must be trivially copyable to be used here.")
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#define VTKM_IS_TRIVIALLY_CONSTRUCTIBLE(...) \
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VTKM_STATIC_ASSERT_MSG(::vtkmstd::is_trivially_constructible<__VA_ARGS__>::value, \
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"Type must be trivially constructible to be used here.")
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#define VTKM_IS_TRIVIALLY_DESTRUCTIBLE(...) \
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VTKM_STATIC_ASSERT_MSG(::vtkmstd::is_trivially_destructible<__VA_ARGS__>::value, \
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"Type must be trivially constructible to be used here.")
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#define VTKM_IS_TRIVIAL(type) \
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VTKM_STATIC_ASSERT_MSG(::vtkmstd::is_trivial<type>::value, \
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"Type must be trivial to be used here.")
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} // namespace vtkmstd
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#endif
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#endif //vtk_m_std_is_trivial_h
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