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Unified Diff: base/memory/ptr_util.h

Issue 1532433002: Add base::MakeUnique to mirror C++14's std::make_unique. (Closed) Base URL: https://chromium.googlesource.com/chromium/src.git@master
Patch Set: Created 5 years ago
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Index: base/memory/ptr_util.h
diff --git a/base/memory/ptr_util.h b/base/memory/ptr_util.h
index 04f2c0258929e74c0bcca89d4433fa6f647a0d28..8747ac9463323865a28eb7d0baf9a6367ab7b5df 100644
--- a/base/memory/ptr_util.h
+++ b/base/memory/ptr_util.h
@@ -6,6 +6,7 @@
#define BASE_MEMORY_PTR_UTIL_H_
#include <memory>
+#include <utility>
namespace base {
@@ -17,6 +18,57 @@ std::unique_ptr<T> WrapUnique(T* ptr) {
return std::unique_ptr<T>(ptr);
}
+namespace internal {
+
+template <typename T>
+struct MakeUniqueResult {
+ using Scalar = std::unique_ptr<T>;
+};
+
+template <typename T>
+struct MakeUniqueResult<T[]> {
+ using Array = std::unique_ptr<T[]>;
+};
+
+template <typename T, size_t N>
+struct MakeUniqueResult<T[N]> {
+ using Invalid = void;
+};
+
+} // namespace internal
+
+// Helper to construct an object wrapped in a std::unique_ptr. This is an
+// implementation of C++14's std::make_unique that can be used in Chrome.
+//
+// MakeUnique<T>(args) should be preferred over WrapUnique(new T(args)): bare
+// calls to `new` should be treated with scrutiny.
Ryan Sleevi 2015/12/15 23:53:40 Is this level of warning needed? That is, it seem
dcheng 2015/12/15 23:59:50 It seems like you could still get the former patte
+//
+// Usage:
+// // ptr is a std::unique_ptr<std::string>
+// auto ptr = MakeUnique<std::string>("hello world!");
+//
+// // arr is a std::unique_ptr<int[]>
+// auto arr = MakeUnique<int[]>(5);
+
+// Overload for non-array types. Arguments are forwarded to T's constructor.
+template <typename T, typename... Args>
+typename internal::MakeUniqueResult<T>::Scalar MakeUnique(Args&&... args) {
+ return std::unique_ptr<T>(new T(std::forward<Args>(args)...));
+}
+
+// Overload for array types of unknown bound, e.g. T[]. The array is allocated
+// with `new T[n]()` and value-initialized: note that this is distinct from
+// `new T[n]`, which default-initializes.
+template <typename T>
+typename internal::MakeUniqueResult<T>::Array MakeUnique(size_t size) {
+ return std::unique_ptr<T>(new typename std::remove_extent<T>::type[size]());
+}
+
+// Overload to reject array types of known bound, e.g. T[n].
+template <typename T, typename... Args>
+typename internal::MakeUniqueResult<T>::Invalid MakeUnique(Args&&... args) =
+ delete;
+
} // namespace base
#endif // BASE_MEMORY_PTR_UTIL_H_
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