From 4a99026cc94ee74963b63e1bd950115ddcfd8cd3 Mon Sep 17 00:00:00 2001
From: Robin Gareus <robin@gareus.org>
Date: Tue, 19 Nov 2024 18:01:54 +0100
Subject: [PATCH] Revert "Replace boost::aligned_storage with alignas
 std::array"

This reverts commit 32ff87f7f6da97830ab002cc64565bafd0b65dc6.

This causes issues on macOS/clang
```
../libs/pbd/pbd/stack_allocator.h:152:53: note: destructor of 'StackAllocator<std::__tree_node<std::__value_type<ARDOUR::DataType, std::map<unsigned int, unsigned int, std::less<unsigned int>, PBD::StackAllocator<std::pair<const unsigned int, unsigned int>, 16>>>, void *>, 2>' is implicitly deleted because field '_buf' has a deleted destructor
  152 |         alignas(16) std::array<value_type, stack_capacity> _buf;
```
---
 libs/pbd/pbd/stack_allocator.h | 19 +++++++++++--------
 1 file changed, 11 insertions(+), 8 deletions(-)

diff --git a/libs/pbd/pbd/stack_allocator.h b/libs/pbd/pbd/stack_allocator.h
index 742cf39b6d..9eed081ec0 100644
--- a/libs/pbd/pbd/stack_allocator.h
+++ b/libs/pbd/pbd/stack_allocator.h
@@ -19,6 +19,7 @@
 #ifndef PBD_STACK_ALLOCATOR_H
 #define PBD_STACK_ALLOCATOR_H
 
+#include <boost/type_traits/aligned_storage.hpp>
 #include <limits>
 
 #include "pbd/libpbd_visibility.h"
@@ -60,22 +61,22 @@ public:
 	};
 
 	StackAllocator ()
-		: _ptr (_buf.data())
+		: _ptr ((pointer)&_buf)
 	{ }
 
 	StackAllocator (const StackAllocator&)
-		: StackAllocator ()
+		: _ptr ((pointer)&_buf)
 	{ }
 
 	template <typename U, size_t other_capacity>
 	StackAllocator (const StackAllocator<U, other_capacity>&)
-		: StackAllocator ()
+		: _ptr ((pointer)&_buf)
 	{ }
 
 	/* inspired by http://howardhinnant.github.io/stack_alloc.h */
 	pointer allocate (size_type n, void* hint = 0)
 	{
-		if (_buf.data() + stack_capacity >= _ptr + n) {
+		if ((pointer)&_buf + stack_capacity >= _ptr + n) {
 			DEBUG_STACK_ALLOC ("Allocate %ld item(s) of size %zu on the stack\n", n, sizeof (T));
 			pointer rv = _ptr;
 			_ptr += n;
@@ -107,12 +108,12 @@ public:
 
 	bool operator== (StackAllocator const& a) const
 	{
-		return _buf.data() == a._buf.data();
+		return &_buf == &a._buf;
 	}
 
 	bool operator!= (StackAllocator const& a) const
 	{
-		return _buf.data() != a._buf.data();
+		return &_buf != &a._buf;
 	}
 
 	template <class U>
@@ -146,10 +147,12 @@ private:
 
 	bool pointer_in_buffer (pointer const p)
 	{
-		return (_buf.data() <= p && p < _buf.data() + stack_capacity);
+		return ((pointer const)&_buf <= p && p < (pointer const)&_buf + stack_capacity);
 	}
 
-	alignas(16) std::array<value_type, stack_capacity> _buf;
+	typedef typename boost::aligned_storage<sizeof (T) * stack_capacity, 16>::type align_t;
+
+	align_t _buf;
 	pointer _ptr;
 };