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This helps inform Nullability inference without needing any special casing. Since ABSL_DIE_IF_NULL is allowed for pointers, smart pointers, or classes marked with ABSL_NULLABILITY_COMPATIBLE we introduce a trait to help add the annotation only when compatible. This trait is kept internal for now out of caution for what we are supporting, though people have asked about it before (see b/394789178). Simple cases are tested by `-Wnonnull` in absl/base/nullability_nc_test.cc. However, it's unclear how to test the complex cases like templates with universal references with the simple compiler `-Wnonnull`. There is a followup nullability inference test (cl/808830606). Since there is Wnullability-completeness, needed to annotate the rest of die_if_null.h PiperOrigin-RevId: 810463021 Change-Id: Id5156996bf3a29a99e689974ac2af7b94b21c460
72 lines
2.3 KiB
C++
72 lines
2.3 KiB
C++
// Copyright 2025 The Abseil Authors
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// https://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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#ifndef ABSL_BASE_INTERNAL_NULLABILITY_TRAITS_H_
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#define ABSL_BASE_INTERNAL_NULLABILITY_TRAITS_H_
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#include <type_traits>
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#include "absl/base/config.h"
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#include "absl/base/nullability.h"
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namespace absl {
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ABSL_NAMESPACE_BEGIN
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namespace base_internal {
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// `value` is true if the type `T` is compatible with nullability annotations
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// (is a raw pointer, a smart pointer, or marked with
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// ABSL_NULLABILITY_COMPATIBLE). Prefer to use the higher-level
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// `AddNonnullIfCompatible` if that is sufficient.
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//
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// NOTE: This should not be used to detect if the compiler is Clang (since
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// Clang is the only compiler that supports nullability annotations).
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#if defined(__clang__) && !defined(__OBJC__) && \
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ABSL_HAVE_FEATURE(nullability_on_classes)
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template <class T, class = void>
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struct IsNullabilityCompatibleType {
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constexpr static bool value = false;
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};
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template <class T>
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struct IsNullabilityCompatibleType<T, std::void_t<absl_nullable T>> {
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constexpr static bool value = true;
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};
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#else
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// False when absl_nullable is a no-op (for non-Clang compilers or Objective-C.)
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template <class T, class = void>
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struct IsNullabilityCompatibleType {
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constexpr static bool value = false;
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};
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#endif
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// A trait to add `absl_nonnull` to a type if it is compatible with nullability
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// annotations.
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template <typename T, bool ShouldAdd = IsNullabilityCompatibleType<T>::value>
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struct AddNonnullIfCompatible;
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template <typename T>
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struct AddNonnullIfCompatible<T, false> {
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using type = T;
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};
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template <typename T>
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struct AddNonnullIfCompatible<T, true> {
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using type = absl_nonnull T;
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};
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} // namespace base_internal
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ABSL_NAMESPACE_END
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} // namespace absl
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#endif // ABSL_BASE_INTERNAL_NULLABILITY_TRAITS_H_
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