From 97b2d9a3fa8f4ea7be9ddb226c13b1d4362eb099 Mon Sep 17 00:00:00 2001
From: schrodingerzhu <i@zhuyi.fan>
Date: Sat, 21 Dec 2024 18:01:48 -0500
Subject: [PATCH] [proxy](7/n) proxy array headers

---
 src/snmalloc/backend_helpers/buddy.h |   2 +-
 src/snmalloc/ds_core/helpers.h       |  16 ++--
 src/snmalloc/ds_core/ptrwrap.h       |   4 +-
 src/snmalloc/ds_core/redblacktree.h  |   5 +-
 src/snmalloc/mem/freelist.h          |   6 +-
 src/snmalloc/mem/remotecache.h       |   9 +-
 src/snmalloc/pal/pal_linux.h         |   4 +-
 src/snmalloc/pal/pal_posix.h         |   4 +-
 src/snmalloc/proxy/array.h           | 118 +++++++++++++++++++++++++++
 src/test/func/memory/memory.cc       |   2 +
 10 files changed, 145 insertions(+), 25 deletions(-)
 create mode 100644 src/snmalloc/proxy/array.h

diff --git a/src/snmalloc/backend_helpers/buddy.h b/src/snmalloc/backend_helpers/buddy.h
index d7406468e..74edc97d8 100644
--- a/src/snmalloc/backend_helpers/buddy.h
+++ b/src/snmalloc/backend_helpers/buddy.h
@@ -23,7 +23,7 @@ namespace snmalloc
       RBTree<Rep> tree{};
     };
 
-    std::array<Entry, MAX_SIZE_BITS - MIN_SIZE_BITS> entries{};
+    proxy::Array<Entry, MAX_SIZE_BITS - MIN_SIZE_BITS> entries{};
     // All RBtrees at or above this index should be empty.
     size_t empty_at_or_above{0};
 
diff --git a/src/snmalloc/ds_core/helpers.h b/src/snmalloc/ds_core/helpers.h
index 9c203ec63..0b50422b4 100644
--- a/src/snmalloc/ds_core/helpers.h
+++ b/src/snmalloc/ds_core/helpers.h
@@ -2,10 +2,10 @@
 
 #include "bits.h"
 #include "snmalloc/ds_core/defines.h"
+#include "snmalloc/proxy/array.h"
 #include "snmalloc/proxy/type_traits.h"
 #include "snmalloc/proxy/utility.h"
 
-#include <array>
 #include <stddef.h>
 
 namespace snmalloc
@@ -50,7 +50,7 @@ namespace snmalloc
     };
 
     static constexpr size_t rlength = bits::next_pow2_const(length);
-    std::array<TWrap, rlength> array;
+    proxy::Array<TWrap, rlength> array;
 
   public:
     constexpr const T& operator[](const size_t i) const
@@ -65,7 +65,7 @@ namespace snmalloc
   };
 #else
   template<size_t length, typename T>
-  using ModArray = std::array<T, length>;
+  using ModArray = proxy::Array<T, length>;
 #endif
 
   /**
@@ -105,7 +105,7 @@ namespace snmalloc
     template<
       typename Fn,
       typename =
-        proxy::enable_if_t<!proxy::is_same_v<std::decay_t<Fn>, function_ref>>>
+        proxy::enable_if_t<!proxy::is_same_v<proxy::decay_t<Fn>, function_ref>>>
     function_ref(Fn&& fn)
     {
       data_ = static_cast<void*>(&fn);
@@ -144,7 +144,7 @@ namespace snmalloc
     /**
      * The buffer that is used to store the formatted output.
      */
-    std::array<char, BufferSize> buffer;
+    proxy::Array<char, BufferSize> buffer;
 
     /**
      * Space in the buffer, excluding a trailing null terminator.
@@ -208,7 +208,7 @@ namespace snmalloc
     /**
      * Append a nullptr
      */
-    void append(std::nullptr_t)
+    void append(decltype(nullptr))
     {
       append("(nullptr)");
     }
@@ -254,7 +254,7 @@ namespace snmalloc
         append_char('-');
         s = 0 - s;
       }
-      std::array<char, 20> buf{{0}};
+      proxy::Array<char, 20> buf{{0}};
       const char digits[] = "0123456789";
       for (long i = static_cast<long>(buf.size() - 1); i >= 0; i--)
       {
@@ -284,7 +284,7 @@ namespace snmalloc
     {
       append_char('0');
       append_char('x');
-      std::array<char, 16> buf{{0}};
+      proxy::Array<char, 16> buf{{0}};
       const char hexdigits[] = "0123456789abcdef";
       // Length of string including null terminator
       static_assert(sizeof(hexdigits) == 0x11);
diff --git a/src/snmalloc/ds_core/ptrwrap.h b/src/snmalloc/ds_core/ptrwrap.h
index 38e268eb6..fcb58dfdf 100644
--- a/src/snmalloc/ds_core/ptrwrap.h
+++ b/src/snmalloc/ds_core/ptrwrap.h
@@ -276,7 +276,7 @@ namespace snmalloc
     /**
      * nullptr is implicitly constructable at any bounds type
      */
-    constexpr SNMALLOC_FAST_PATH CapPtr(const std::nullptr_t n)
+    constexpr SNMALLOC_FAST_PATH CapPtr(const decltype(nullptr) n)
     : unsafe_capptr(n)
     {}
 
@@ -465,7 +465,7 @@ namespace snmalloc
     /**
      * nullptr is constructable at any bounds type
      */
-    constexpr SNMALLOC_FAST_PATH AtomicCapPtr(const std::nullptr_t n)
+    constexpr SNMALLOC_FAST_PATH AtomicCapPtr(const decltype(nullptr) n)
     : unsafe_capptr(n)
     {}
 
diff --git a/src/snmalloc/ds_core/redblacktree.h b/src/snmalloc/ds_core/redblacktree.h
index 37b90ddb2..251fd3caa 100644
--- a/src/snmalloc/ds_core/redblacktree.h
+++ b/src/snmalloc/ds_core/redblacktree.h
@@ -1,6 +1,7 @@
 #pragma once
 
-#include <array>
+#include "snmalloc/proxy/array.h"
+
 #include <stddef.h>
 #include <stdint.h>
 
@@ -260,7 +261,7 @@ namespace snmalloc
     {
       friend class RBTree;
 
-      std::array<RBStep, 128> path;
+      proxy::Array<RBStep, 128> path;
       size_t length = 0;
 
       RBPath(typename Rep::Handle root)
diff --git a/src/snmalloc/mem/freelist.h b/src/snmalloc/mem/freelist.h
index 6e47ee20f..298c14ef9 100644
--- a/src/snmalloc/mem/freelist.h
+++ b/src/snmalloc/mem/freelist.h
@@ -701,11 +701,11 @@ namespace snmalloc
        */
 
       // Pointer to the first element.
-      std::array<void*, LENGTH> head{nullptr};
+      proxy::Array<void*, LENGTH> head{nullptr};
       // Pointer to the reference to the last element.
       // In the empty case end[i] == &head[i]
       // This enables branch free enqueuing.
-      std::array<void**, LENGTH> end{nullptr};
+      proxy::Array<void**, LENGTH> end{nullptr};
 
       [[nodiscard]] Object::BQueuePtr<BQueue>* cast_end(uint32_t ix) const
       {
@@ -724,7 +724,7 @@ namespace snmalloc
       }
 
       SNMALLOC_NO_UNIQUE_ADDRESS
-      std::array<uint16_t, RANDOM ? 2 : (TRACK_LENGTH ? 1 : 0)> length{};
+      proxy::Array<uint16_t, RANDOM ? 2 : (TRACK_LENGTH ? 1 : 0)> length{};
 
     public:
       constexpr Builder() = default;
diff --git a/src/snmalloc/mem/remotecache.h b/src/snmalloc/mem/remotecache.h
index 02b843e12..dd4812bc5 100644
--- a/src/snmalloc/mem/remotecache.h
+++ b/src/snmalloc/mem/remotecache.h
@@ -6,10 +6,9 @@
 #include "metadata.h"
 #include "remoteallocator.h"
 #include "sizeclasstable.h"
+#include "snmalloc/proxy/array.h"
 #include "snmalloc/proxy/atomic.h"
 
-#include <array>
-
 namespace snmalloc
 {
 
@@ -33,8 +32,8 @@ namespace snmalloc
   {
     static_assert(RINGS > 0);
 
-    std::array<freelist::Builder<false, true>, RINGS> open_builder;
-    std::array<address_t, RINGS> open_meta = {0};
+    proxy::Array<freelist::Builder<false, true>, RINGS> open_builder;
+    proxy::Array<address_t, RINGS> open_meta = {0};
 
     SNMALLOC_FAST_PATH size_t
     ring_set(typename Config::PagemapEntry::SlabMetadata* meta)
@@ -191,7 +190,7 @@ namespace snmalloc
   template<typename Config>
   struct RemoteDeallocCache
   {
-    std::array<freelist::Builder<false>, REMOTE_SLOTS> list;
+    proxy::Array<freelist::Builder<false>, REMOTE_SLOTS> list;
 
     RemoteDeallocCacheBatchingImpl<Config> batching;
 
diff --git a/src/snmalloc/pal/pal_linux.h b/src/snmalloc/pal/pal_linux.h
index 133e00674..16090c839 100644
--- a/src/snmalloc/pal/pal_linux.h
+++ b/src/snmalloc/pal/pal_linux.h
@@ -183,8 +183,8 @@ namespace snmalloc
       // protected routine.
       if (false == syscall_not_working.load(proxy::memory_order_relaxed))
       {
-        auto current = std::begin(buffer);
-        auto target = std::end(buffer);
+        auto current = proxy::begin(buffer);
+        auto target = proxy::end(buffer);
         while (auto length = target - current)
         {
           // Reading data via syscall from system entropy pool.
diff --git a/src/snmalloc/pal/pal_posix.h b/src/snmalloc/pal/pal_posix.h
index ac0e4c6d9..118e30b53 100644
--- a/src/snmalloc/pal/pal_posix.h
+++ b/src/snmalloc/pal/pal_posix.h
@@ -419,8 +419,8 @@ namespace snmalloc
       auto fd = open("/dev/urandom", flags, 0);
       if (fd > 0)
       {
-        auto current = std::begin(buffer);
-        auto target = std::end(buffer);
+        auto current = proxy::begin(buffer);
+        auto target = proxy::end(buffer);
         while (auto length = static_cast<size_t>(target - current))
         {
           ret = read(fd, current, length);
diff --git a/src/snmalloc/proxy/array.h b/src/snmalloc/proxy/array.h
new file mode 100644
index 000000000..7c4898fdf
--- /dev/null
+++ b/src/snmalloc/proxy/array.h
@@ -0,0 +1,118 @@
+#pragma once
+
+#include "snmalloc/ds_core/defines.h"
+
+#ifndef SNMALLOC_USE_SELF_VENDORED_STL
+#  define SNMALLOC_USE_SELF_VENDORED_STL 0
+#endif
+
+#if SNMALLOC_USE_SELF_VENDORED_STL
+
+#  if !defined(__GNUC__) && !defined(__clang__)
+#    error "cannot use vendored STL without GNU/Clang extensions"
+#  endif
+
+#  include <stddef.h>
+
+namespace snmalloc
+{
+  namespace proxy
+  {
+    template<typename T, size_t N>
+    struct Array
+    {
+      // N is potentially 0, so we mark it with __extension__ attribute.
+      // expose this to public to allow aggregate initialization
+      __extension__ T storage[N];
+
+      [[nodiscard]] constexpr SNMALLOC_FAST_PATH size_t size() const
+      {
+        return N;
+      }
+
+      constexpr T& operator[](size_t i)
+      {
+        return storage[i];
+      }
+
+      constexpr const T& operator[](size_t i) const
+      {
+        return storage[i];
+      }
+
+      using value_type = T;
+      using size_type = size_t;
+      using iterator = T*;
+      using const_iterator = const T*;
+
+      [[nodiscard]] constexpr SNMALLOC_FAST_PATH iterator begin()
+      {
+        return &storage[0];
+      }
+
+      [[nodiscard]] constexpr SNMALLOC_FAST_PATH const_iterator begin() const
+      {
+        return &storage[0];
+      }
+
+      [[nodiscard]] constexpr SNMALLOC_FAST_PATH iterator end()
+      {
+        return &storage[N];
+      }
+
+      [[nodiscard]] constexpr SNMALLOC_FAST_PATH const_iterator end() const
+      {
+        return &storage[N];
+      }
+
+      [[nodiscard]] constexpr SNMALLOC_FAST_PATH T* data()
+      {
+        return &storage[0];
+      }
+
+      [[nodiscard]] constexpr SNMALLOC_FAST_PATH const T* data() const
+      {
+        return &storage[0];
+      }
+    };
+
+    template<typename T, size_t N>
+    constexpr T* begin(Array<T, N>& a)
+    {
+      return a.begin();
+    }
+
+    template<typename T, size_t N>
+    constexpr T* end(Array<T, N>& a)
+    {
+      return a.end();
+    }
+
+    template<typename T, size_t N>
+    constexpr const T* begin(const Array<T, N>& a)
+    {
+      return a.begin();
+    }
+
+    template<typename T, size_t N>
+    constexpr const T* end(const Array<T, N>& a)
+    {
+      return a.end();
+    }
+  } // namespace proxy
+} // namespace snmalloc
+#else
+#  include <array>
+
+namespace snmalloc
+{
+  namespace proxy
+  {
+    template<typename T, size_t N>
+    using Array = std::array<T, N>;
+
+    using std::begin;
+    using std::end;
+  } // namespace proxy
+} // namespace snmalloc
+#endif
diff --git a/src/test/func/memory/memory.cc b/src/test/func/memory/memory.cc
index c85659eab..6b52e89a8 100644
--- a/src/test/func/memory/memory.cc
+++ b/src/test/func/memory/memory.cc
@@ -1,3 +1,4 @@
+#include <array>
 #include <iostream>
 #include <snmalloc/snmalloc.h>
 #include <test/opt.h>
@@ -5,6 +6,7 @@
 #include <test/xoroshiro.h>
 #include <unordered_set>
 #include <vector>
+
 #if ((defined(__linux__) && !defined(__ANDROID__)) || defined(__sun)) || \
   defined(__OpenBSD__) && !defined(SNMALLOC_QEMU_WORKAROUND)
 /*