From 0f2eedd4fb3946ed2a776b3baccf2ea0cd98cf6a Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Tam=C3=A1s=20B=C3=A1lint=20Misius?= <lbphacker@gmail.com>
Date: Sat, 23 Oct 2021 09:38:58 +0200
Subject: [PATCH] Make thread_local replacement for MinGW slightly nicer

---
 src/common/tpt-thread-local.cpp | 78 +++++++++++++--------------------
 src/common/tpt-thread-local.h   | 63 +++++++++++++++++---------
 2 files changed, 73 insertions(+), 68 deletions(-)

diff --git a/src/common/tpt-thread-local.cpp b/src/common/tpt-thread-local.cpp
index cde7ec95c..0a53422c1 100644
--- a/src/common/tpt-thread-local.cpp
+++ b/src/common/tpt-thread-local.cpp
@@ -5,58 +5,41 @@
 # include <cstdlib>
 # include <cassert>
 
-static pthread_once_t once = PTHREAD_ONCE_INIT;
-static pthread_key_t key;
-
-struct ThreadLocalCommon
+void *ThreadLocalCommon::Get() const
 {
-	size_t size;
-	void (*ctor)(void *);
-	void (*dtor)(void *);
-	size_t padding;
-};
-static_assert(sizeof(ThreadLocalCommon) == 0x20, "fix me");
+	// https://stackoverflow.com/questions/16552710/how-do-you-get-the-start-and-end-addresses-of-a-custom-elf-section
+	extern ThreadLocalCommon __start_tpt_tls;
+	extern ThreadLocalCommon __stop_tpt_tls;
+	static pthread_once_t once = PTHREAD_ONCE_INIT;
+	static pthread_key_t key;
 
-struct ThreadLocalEntry
-{
-	void *ptr;
-};
-
-// https://stackoverflow.com/questions/16552710/how-do-you-get-the-start-and-end-addresses-of-a-custom-elf-section
-extern ThreadLocalCommon __start_tpt_tls;
-extern ThreadLocalCommon __stop_tpt_tls;
-
-static void ThreadLocalDestroy(void *opaque)
-{
-	auto *staticsBegin = &__start_tpt_tls;
-	auto *staticsEnd = &__stop_tpt_tls;
-	auto staticsCount = staticsEnd - staticsBegin;
-	auto *liveObjects = reinterpret_cast<ThreadLocalEntry *>(opaque);
-	if (liveObjects)
+	struct ThreadLocalEntry
 	{
-		for (auto i = 0; i < staticsCount; ++i)
-		{
-			if (liveObjects[i].ptr)
-			{
-				staticsBegin[i].dtor(liveObjects[i].ptr);
-				free(liveObjects[i].ptr);
-			}
-		}
-		free(liveObjects);
-	}
-}
+		void *ptr;
+	};
 
-static void ThreadLocalCreate()
-{
-	assert(!pthread_key_create(&key, ThreadLocalDestroy));
-}
-
-void *ThreadLocalGet(void *opaque)
-{
 	auto *staticsBegin = &__start_tpt_tls;
 	auto *staticsEnd = &__stop_tpt_tls;
-	auto *staticsOpaque = reinterpret_cast<ThreadLocalCommon *>(opaque);
-	pthread_once(&once, ThreadLocalCreate);
+	pthread_once(&once, []() -> void {
+		assert(!pthread_key_create(&key, [](void *opaque) -> void {
+			auto *staticsBegin = &__start_tpt_tls;
+			auto *staticsEnd = &__stop_tpt_tls;
+			auto staticsCount = staticsEnd - staticsBegin;
+			auto *liveObjects = reinterpret_cast<ThreadLocalEntry *>(opaque);
+			if (liveObjects)
+			{
+				for (auto i = 0; i < staticsCount; ++i)
+				{
+					if (liveObjects[i].ptr)
+					{
+						staticsBegin[i].dtor(liveObjects[i].ptr);
+						free(liveObjects[i].ptr);
+					}
+				}
+				free(liveObjects);
+			}
+		}));
+	});
 	auto *liveObjects = reinterpret_cast<ThreadLocalEntry *>(pthread_getspecific(key));
 	if (!liveObjects)
 	{
@@ -65,7 +48,7 @@ void *ThreadLocalGet(void *opaque)
 		assert(liveObjects);
 		assert(!pthread_setspecific(key, reinterpret_cast<void *>(liveObjects)));
 	}
-	auto idx = staticsOpaque - staticsBegin;
+	auto idx = this - staticsBegin;
 	auto &entry = liveObjects[idx];
 	if (!entry.ptr)
 	{
@@ -75,5 +58,4 @@ void *ThreadLocalGet(void *opaque)
 	}
 	return entry.ptr;
 }
-
 #endif
diff --git a/src/common/tpt-thread-local.h b/src/common/tpt-thread-local.h
index 01a05c02e..e6b6586f6 100644
--- a/src/common/tpt-thread-local.h
+++ b/src/common/tpt-thread-local.h
@@ -4,39 +4,62 @@
 #ifdef __MINGW32__
 # include <cstddef>
 
-template<class Type>
-class ThreadLocal
+class ThreadLocalCommon
 {
-	static void Ctor(Type *type)
-	{
-		new (type) Type();
-	}
+	ThreadLocalCommon(const ThreadLocalCommon &other) = delete;
+	ThreadLocalCommon &operator =(const ThreadLocalCommon &other) = delete;
 
-	static void Dtor(Type *type)
-	{
-		type->~Type();
-	}
-
-	size_t size = sizeof(Type);
-	void (*ctor)(Type *) = Ctor;
-	void (*dtor)(Type *) = Dtor;
+protected:
+	size_t size;
+	void (*ctor)(void *);
+	void (*dtor)(void *);
 	size_t padding;
 
+	void *Get() const;
+
 public:
-	Type *operator &()
+	ThreadLocalCommon() = default;
+
+	static constexpr size_t Alignment = 0x20;
+};
+// * If this fails, add or remove padding fields, possibly change Alignment to a larger power of 2.
+static_assert(sizeof(ThreadLocalCommon) == ThreadLocalCommon::Alignment, "fix me");
+
+template<class Type>
+class ThreadLocal : public ThreadLocalCommon
+{
+	static void Ctor(void *type)
 	{
-		static_assert(sizeof(ThreadLocal<Type>) == 0x20, "fix me");
-		void *ThreadLocalGet(void *opaque);
-		return reinterpret_cast<Type *>(ThreadLocalGet(reinterpret_cast<void *>(this)));
+		new(type) Type();
 	}
 
-	operator Type &()
+	static void Dtor(void *type)
+	{
+		reinterpret_cast<Type *>(type)->~Type();
+	}
+
+public:
+	ThreadLocal()
+	{
+		// * If this fails, you're out of luck.
+		static_assert(sizeof(ThreadLocal<Type>) == sizeof(ThreadLocalCommon), "fix me");
+		size = sizeof(Type);
+		ctor = Ctor;
+		dtor = Dtor;
+	}
+
+	Type *operator &() const
+	{
+		return reinterpret_cast<Type *>(Get());
+	}
+
+	operator Type &() const
 	{
 		return *(this->operator &());
 	}
 };
 
-# define THREAD_LOCAL(Type, tl) ThreadLocal<Type> tl __attribute__((section("tpt_tls"))) __attribute__((aligned(0x20)))
+# define THREAD_LOCAL(Type, tl) const ThreadLocal<Type> tl __attribute__((section("tpt_tls"), aligned(ThreadLocalCommon::Alignment)))
 #else
 # define THREAD_LOCAL(Type, tl) thread_local Type tl
 #endif