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From: Jonathan Wakely <redi@gcc.gnu.org> To: gcc-cvs@gcc.gnu.org, libstdc++-cvs@gcc.gnu.org Subject: [gcc r14-291] libstdc++: Improve doxygen docs for <memory_resource> Date: Thu, 27 Apr 2023 10:30:03 +0000 (GMT) [thread overview] Message-ID: <20230427103003.D4022385842B@sourceware.org> (raw) https://gcc.gnu.org/g:afcf2b09b8317d2777f44e830c3b8de1791312d5 commit r14-291-gafcf2b09b8317d2777f44e830c3b8de1791312d5 Author: Jonathan Wakely <jwakely@redhat.com> Date: Wed Apr 26 22:50:03 2023 +0100 libstdc++: Improve doxygen docs for <memory_resource> libstdc++-v3/ChangeLog: * include/bits/memory_resource.h: Improve doxygen comments. * include/std/memory_resource: Likewise. Diff: --- libstdc++-v3/include/bits/memory_resource.h | 12 ++++++ libstdc++-v3/include/std/memory_resource | 63 +++++++++++++++++++++++++++++ 2 files changed, 75 insertions(+) diff --git a/libstdc++-v3/include/bits/memory_resource.h b/libstdc++-v3/include/bits/memory_resource.h index 1b9e51ddbbd..f12555d4215 100644 --- a/libstdc++-v3/include/bits/memory_resource.h +++ b/libstdc++-v3/include/bits/memory_resource.h @@ -53,6 +53,11 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION namespace pmr { /// Class memory_resource + /** + * @ingroup pmr + * @headerfile memory_resource + * @since C++17 + */ class memory_resource { static constexpr size_t _S_max_align = alignof(max_align_t); @@ -104,6 +109,13 @@ namespace pmr #endif // C++17 23.12.3 Class template polymorphic_allocator + + /// Class template polymorphic_allocator + /** + * @ingroup pmr + * @headerfile memory_resource + * @since C++17 + */ template<typename _Tp> class polymorphic_allocator { diff --git a/libstdc++-v3/include/std/memory_resource b/libstdc++-v3/include/std/memory_resource index 00859262470..fdfc23c95ed 100644 --- a/libstdc++-v3/include/std/memory_resource +++ b/libstdc++-v3/include/std/memory_resource @@ -24,6 +24,9 @@ /** @file include/memory_resource * This is a Standard C++ Library header. + * + * This header declares the @ref pmr (std::pmr) memory resources. + * @ingroup pmr */ #ifndef _GLIBCXX_MEMORY_RESOURCE @@ -35,6 +38,25 @@ #if __cplusplus >= 201703L +/** + * @defgroup pmr Polymorphic memory resources + * + * @anchor pmr + * @ingroup memory + * @since C++17 + * + * Memory resources are classes that implement the `std::pmr::memory_resource` + * interface for allocating and deallocating memory. Unlike traditional C++ + * allocators, memory resources are not value types and are used via pointers + * to the abstract base class. They are only responsible for allocating and + * deallocating, not for construction and destruction of objects. As a result, + * memory resources just allocate raw memory as type `void*` and are not + * templates that allocate/deallocate and construct/destroy a specific type. + * + * The class template `std::pmr::polymorphic_allocator` is an allocator that + * uses a memory resource for its allocations. + */ + #include <bits/memory_resource.h> #include <vector> // vector #include <shared_mutex> // shared_mutex @@ -63,6 +85,11 @@ namespace pmr // Global memory resources /// A pmr::memory_resource that uses `new` to allocate memory + /** + * @ingroup pmr + * @headerfile memory_resource + * @since C++17 + */ [[nodiscard, __gnu__::__returns_nonnull__, __gnu__::__const__]] memory_resource* new_delete_resource() noexcept; @@ -91,6 +118,11 @@ namespace pmr class monotonic_buffer_resource; /// Parameters for tuning a pool resource's behaviour. + /** + * @ingroup pmr + * @headerfile memory_resource + * @since C++17 + */ struct pool_options { /** @brief Upper limit on number of blocks in a chunk. @@ -152,6 +184,11 @@ namespace pmr #ifdef _GLIBCXX_HAS_GTHREADS /// A thread-safe memory resource that manages pools of fixed-size blocks. + /** + * @ingroup pmr + * @headerfile memory_resource + * @since C++17 + */ class synchronized_pool_resource : public memory_resource { public: @@ -218,6 +255,11 @@ namespace pmr #endif /// A non-thread-safe memory resource that manages pools of fixed-size blocks. + /** + * @ingroup pmr + * @headerfile memory_resource + * @since C++17 + */ class unsynchronized_pool_resource : public memory_resource { public: @@ -275,6 +317,27 @@ namespace pmr _Pool* _M_pools = nullptr; }; + /// A memory resource that allocates from a fixed-size buffer. + /** + * The main feature of a `pmr::monotonic_buffer_resource` is that its + * `do_deallocate` does nothing. This makes it very fast because there is no + * need to manage a free list, and every allocation simply returns a new + * block of memory, rather than searching for a suitably-sized free block. + * Because deallocating is a no-op, the amount of memory used by the resource + * only grows until `release()` (or the destructor) is called to return all + * memory to upstream. + * + * A `monotonic_buffer_resource` can be initialized with a buffer that + * will be used to satisfy all allocation requests, until the buffer is full. + * After that a new buffer will be allocated from the upstream resource. + * By using a stack buffer and `pmr::null_memory_resource()` as the upstream + * you can get a memory resource that only uses the stack and never + * dynamically allocates. + * + * @ingroup pmr + * @headerfile memory_resource + * @since C++17 + */ class monotonic_buffer_resource : public memory_resource { public:
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