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f2bdc2176f
We would like to record additional information in the find-package stack, but we don't have the information at the point a stack entry is created. The most sane way to handle this appears to be making the stack mutable, at least under specific circumstances. To facilitate this, we need a mutable stack type. Refactor cmConstStack into cmStack, with the ability to either allow or forbid mutation of its data. Re-add cmConstStack as a type alias. This doesn't yet allow mutating cmFindPackageStack, but it's a necessary step toward being able to do so.
62 lines
1.7 KiB
C++
62 lines
1.7 KiB
C++
/* Distributed under the OSI-approved BSD 3-Clause License. See accompanying
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file LICENSE.rst or https://cmake.org/licensing for details. */
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#pragma once
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#include "cmConfigure.h" // IWYU pragma: keep
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#include <memory>
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#include <type_traits>
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enum class cmStackType
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{
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Const,
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Mutable,
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};
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template <typename T, cmStackType Mutable>
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struct cmStackEntry;
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/** Base class template for CRTP to represent a stack of values.
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Copies of the stack <i>share data</i>; mutating data on one copy will
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change the data on <i>all</i> copies. */
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template <typename T, typename Stack,
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cmStackType Mutable = cmStackType::Mutable>
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class cmStack
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{
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using Entry = cmStackEntry<T, Mutable>;
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std::shared_ptr<Entry const> TopEntry;
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public:
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/** Default-construct an empty stack. */
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cmStack();
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/** Get a stack with the given call context added to the top. */
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Stack Push(T value) const;
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/** Get a stack with the top level removed.
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May not be called until after a matching Push. */
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Stack Pop() const;
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/** Get the value at the top of the stack.
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This may be called only if Empty() would return false. */
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T const& Top() const;
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template <bool E = (Mutable == cmStackType::Mutable)>
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typename std::enable_if<E, T>::type& Top();
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/** Return true if this stack is empty. */
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bool Empty() const;
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protected:
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using Base = cmStack<T, Stack, Mutable>;
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cmStack(std::shared_ptr<Entry const> parent, T value);
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cmStack(std::shared_ptr<Entry const> top);
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};
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/** Specialization of cmStack for CRTP to represent a stack of constant values.
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Provide value semantics, but use efficient reference-counting underneath
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to avoid copies. */
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template <typename T, typename Stack>
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using cmConstStack = cmStack<T const, Stack, cmStackType::Const>;
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