Rewrite the selector table in C++.

This replaces a few home-grown datastructures with third-party ones that
get a lot more testing:

 - The home-grown hopscotch hash table is moved to using robin map.  The
   original was designed to be lock free, but we've been using it behind
   a lock for ages.
 - The selector list is now a std::vector.
 - The types list now use std::forward_list.

This also removes a couple of code paths that haven't been used since we
started using the new ABI data structures internally and upgrading at
load time.

The new code tries to differentiate in the static type system between
registered and unregistered selectors.  The check for whether a selector
is registered is fragile and depends on no selector being mapped or
allocated in memory below the total number of selectors.  This check can
now disappear on most code paths.

On a single test machine (not guaranteed to be representative) the test
suite now completes around 20% faster.

.github/workflows/main.yml

@@ -50,7 +50,7 @@ jobs:
         run: |
           export LDFLAGS=-L/usr/lib/llvm-${{ matrix.llvm-version }}/lib/
           ls -lahR /usr/lib/llvm-${{ matrix.llvm-version }}/lib/
-          cmake -B ${{github.workspace}}/build -DCMAKE_BUILD_TYPE=${{matrix.build-type}} -G Ninja -DCMAKE_C_COMPILER=clang-${{matrix.llvm-version}} -DCMAKE_ASM_COMPILER=clang-${{matrix.llvm-version}} -DCMAKE_CXX_COMPILER=clang++-${{matrix.llvm-version}} -DCMAKE_CXX_FLAGS="-stdlib=${{matrix.cxxlib}}"
+          cmake -B ${{github.workspace}}/build -DCMAKE_BUILD_TYPE=${{matrix.build-type}} -G Ninja -DTESTS=ON -DCMAKE_C_COMPILER=clang-${{matrix.llvm-version}} -DCMAKE_ASM_COMPILER=clang-${{matrix.llvm-version}} -DCMAKE_CXX_COMPILER=clang++-${{matrix.llvm-version}} -DCMAKE_CXX_FLAGS="-stdlib=${{matrix.cxxlib}}"
         # Build with a nice ninja status line
       - name: Build
         working-directory: ${{github.workspace}}/build

ANNOUNCE

@@ -31,10 +31,10 @@ https://github.com/gnustep/libobjc2/archive/v2.2.tar.gz
 
 The submodule is available from:
 
-https://github.com/Tessil/robin-map/archive/757de82.zip
-https://github.com/Tessil/robin-map/archive/757de82.tar.gz
+https://github.com/Tessil/robin-map/archive/d37a410.zip
+https://github.com/Tessil/robin-map/archive/d37a410.tar.gz
 
-This will extract as robin-map-757de829927489bee55ab02147484850c687b620.
+This will extract as robin-map-d37a41003bfbc7e12e34601f93c18ca2ff6d7c07.
 You must move the contents of that directory into third_party/robin_map in the
 libobjc2 tree.
 

CMakeLists.txt

@@ -67,7 +67,6 @@ set(libobjc_C_SRCS
 	protocol.c
 	runtime.c
 	sarray2.c
-	selector_table.c
 	sendmsg2.c
 	)
 set(libobjc_HDRS
@@ -95,6 +94,9 @@ set(libBlocksRuntime_COMPATIBILITY_HDRS
 	Block.h
 	Block_private.h
 	)
+set(libobjc_CXX_SRCS
+	selector_table.cc
+	)
 # Windows does not use DWARF EH
 if (WIN32)
 	list(APPEND libobjc_CXX_SRCS eh_win32_msvc.cc)

loader.c

@@ -72,9 +72,9 @@ static void init_runtime(void)
 		INIT_LOCK(runtime_mutex);
 		// Create the various tables that the runtime needs.
 		init_selector_tables();
+		init_dispatch_tables();
 		init_protocol_table();
 		init_class_tables();
-		init_dispatch_tables();
 		init_alias_table();
 		init_arc();
 		init_trampolines();

lock.h

@@ -78,4 +78,37 @@ extern mutex_t runtime_mutex;
 #define UNLOCK_RUNTIME() UNLOCK(&runtime_mutex)
 #define LOCK_RUNTIME_FOR_SCOPE() LOCK_FOR_SCOPE(&runtime_mutex)
 
+#ifdef __cplusplus
+/**
+ * C++ wrapper around our mutex, for use with std::lock_guard and friends.
+ */
+class RecursiveMutex
+{
+	/// The underlying mutex
+	mutex_t mutex;
+
+	public:
+	/**
+	 * Explicit initialisation of the underlying lock, so that this can be a
+	 * global.
+	 */
+	void init()
+	{
+		INIT_LOCK(mutex);
+	}
+
+	/// Acquire the lock.
+	void lock()
+	{
+		LOCK(&mutex);
+	}
+
+	/// Release the lock.
+	void unlock()
+	{
+		UNLOCK(&mutex);
+	}
+};
+#endif
+
 #endif // __LIBOBJC_LOCK_H_INCLUDED__

pool.hh

@@ -0,0 +1,45 @@
+#pragma once
+#ifdef _WIN32
+#include "safewindows.h"
+#if defined(WINAPI_FAMILY) && WINAPI_FAMILY != WINAPI_FAMILY_DESKTOP_APP && _WIN32_WINNT >= 0x0A00
+// Prefer the *FromApp versions when we're being built in a Windows Store App context on
+// Windows >= 10. *FromApp require the application to be manifested for "codeGeneration".
+#define VirtualAlloc VirtualAllocFromApp
+#define VirtualProtect VirtualProtectFromApp
+#endif // App family partition
+
+inline void *allocate_pages(size_t size)
+{
+	return VirtualAlloc(nullptr, size, MEM_COMMIT | MEM_RESERVE, PAGE_READWRITE);
+}
+
+#else
+#include <sys/mman.h>
+inline void *allocate_pages(size_t size)
+{
+	void *ret = mmap(nullptr, size, PROT_READ | PROT_WRITE, MAP_PRIVATE | MAP_ANON, -1, 0);
+	return ret == MAP_FAILED ? nullptr : ret;
+
+}
+#endif
+
+template<typename T>
+class PoolAllocate
+{
+	static constexpr size_t PageSize = 4096;
+	static constexpr size_t ChunkSize = sizeof(T) * PageSize;
+	static inline size_t index = PageSize;
+	static inline T *buffer = nullptr;
+	public:
+	static T *allocate()
+	{
+		if (index == PageSize)
+		{
+			index = 0;
+			buffer = static_cast<T*>(allocate_pages(ChunkSize));
+		}
+		return &buffer[index++];
+	}
+};
+
+

selector.h

@@ -1,21 +1,5 @@
 #ifndef OBJC_SELECTOR_H_INCLUDED
 #define OBJC_SELECTOR_H_INCLUDED
-/**
- * Structure used to store the types for a selector.  This allows for a quick
- * test to see whether a selector is polymorphic and allows enumeration of all
- * type encodings for a given selector.
- *
- * This is the same size as an objc_selector, so we can allocate them from the
- * objc_selector pool.
- *
- * Note: For ABI v10, we can probably do something a bit more sensible here and
- * make selectors into a linked list.
- */
-struct sel_type_list
-{
-	const char *value;
-	struct sel_type_list *next;
-};
 
 /**
  * Structure used to store selectors in the list.
@@ -60,17 +44,20 @@ static SEL sel_getUntyped(SEL aSel)
 	return sel_registerTypedName_np(sel_getName(aSel), 0);
 }
 
-/**
- * Returns whether a selector is mapped.  
- */
-BOOL isSelRegistered(SEL sel);
-
+#ifdef __cplusplus
+extern "C"
+{
+#endif
 /**
  * Registers the selector.  This selector may be returned later, so it must not
  * be freed.
  */
 SEL objc_register_selector(SEL aSel);
 
+#ifdef __cplusplus
+}
+#endif
+
 /**
  * SELECTOR() macro to work around the fact that GCC hard-codes the type of
  * selectors.  This is functionally equivalent to @selector(), but it ensures