Make allocator arguments const-ref

[asuessenbach]

Resolves #2315.

[rwols]

I checked out this branch and I can confirm that this branch has the desired behavior (would close #2315).

I verified this by changing the test in tests/DeviceFunctions/DeviceFunctions.cpp in the below diff. The function createCommandBuffers in this diff does not compile on the main branch while it does compile on the const_ref_allocators branch 👍 perhaps you can add these changes to DeviceFunctions.cpp?

diff --git a/tests/DeviceFunctions/CMakeLists.txt b/tests/DeviceFunctions/CMakeLists.txt
index 718e7ab..ba6d114 100644
--- a/tests/DeviceFunctions/CMakeLists.txt
+++ b/tests/DeviceFunctions/CMakeLists.txt
@@ -1,4 +1,4 @@
-# Copyright(c) 2018, NVIDIA CORPORATION. All rights reserved.
+# Copyright(c) 2026, NVIDIA CORPORATION. All rights reserved.
 #
 # Licensed under the Apache License, Version 2.0 (the "License");
 # you may not use this file except in compliance with the License.
diff --git a/tests/DeviceFunctions/DeviceFunctions.cpp b/tests/DeviceFunctions/DeviceFunctions.cpp
index 1c11e8f..2cefc82 100644
--- a/tests/DeviceFunctions/DeviceFunctions.cpp
+++ b/tests/DeviceFunctions/DeviceFunctions.cpp
@@ -1,4 +1,4 @@
-// Copyright(c) 2018, NVIDIA CORPORATION. All rights reserved.
+// Copyright(c) 2026, NVIDIA CORPORATION. All rights reserved.
 //
 // Licensed under the Apache License, Version 2.0 (the "License");
 // you may not use this file except in compliance with the License.
@@ -41,6 +41,17 @@
 static char const * AppName    = "DeviceFunctions";
 static char const * EngineName = "Vulkan.hpp";
 
+template <
+    class Dispatch = VULKAN_HPP_DEFAULT_DISPATCHER_TYPE,
+    class Alloc = std::allocator<vk::UniqueHandle<vk::CommandBuffer, Dispatch>>>
+std::vector<vk::UniqueHandle<vk::CommandBuffer, Dispatch>, Alloc>
+createCommandBuffers(const vk::Device &device,
+                     const vk::CommandBufferAllocateInfo &allocateInfo,
+                     const Alloc &alloc = Alloc(),
+                     const Dispatch &d = VULKAN_HPP_DEFAULT_DISPATCHER) {
+  return device.allocateCommandBuffersUnique(allocateInfo, alloc, d);
+}
+
 int main( int /*argc*/, char ** /*argv*/ )
 {
   try
@@ -70,15 +81,15 @@ int main( int /*argc*/, char ** /*argv*/ )
 
     uint64_t handle = device->getAccelerationStructureHandleNV<uint8_t>( {}, VULKAN_HPP_DISPATCH_LOADER_DYNAMIC_TYPE() );
 
-    std::vector<vk::UniqueCommandBuffer>::allocator_type vectorAllocator;
-    vk::UniqueCommandBuffer                              commandBuffer =
-      std::move( device->allocateCommandBuffersUnique( {}, vectorAllocator, VULKAN_HPP_DISPATCH_LOADER_STATIC_TYPE() ).front() );
-
+    std::vector<vk::UniqueCommandBuffer> vector;
+    vector = createCommandBuffers(device.get(), {}, vector.get_allocator(), VULKAN_HPP_DISPATCH_LOADER_STATIC_TYPE());
+    vk::UniqueCommandBuffer commandBuffer = std::move(vector.front());
     commandBuffer->begin( vk::CommandBufferBeginInfo() );
 
-    std::vector<vk::UniqueHandle<vk::CommandBuffer, VULKAN_HPP_DISPATCH_LOADER_DYNAMIC_TYPE>>::allocator_type dynamicVectorAllocator;
-    vk::UniqueHandle<vk::CommandBuffer, VULKAN_HPP_DISPATCH_LOADER_DYNAMIC_TYPE>                              dynamicCommandBuffer =
-      std::move( device->allocateCommandBuffersUnique( {}, dynamicVectorAllocator, VULKAN_HPP_DISPATCH_LOADER_DYNAMIC_TYPE() ).front() );
+    std::vector<vk::UniqueHandle<vk::CommandBuffer, VULKAN_HPP_DISPATCH_LOADER_DYNAMIC_TYPE>> dynamicVector;
+    dynamicVector = createCommandBuffers(device.get(), {}, dynamicVector.get_allocator(), VULKAN_HPP_DISPATCH_LOADER_DYNAMIC_TYPE());
+
+    vk::UniqueHandle<vk::CommandBuffer, VULKAN_HPP_DISPATCH_LOADER_DYNAMIC_TYPE> dynamicCommandBuffer = std::move(dynamicVector.front());
 
     vk::Buffer       buffer       = device->createBuffer( {} );
     vk::UniqueBuffer uniqueBuffer = vk::UniqueBuffer( buffer, *device );

[rwols]

Well, when trying to run this test it segfaults at the vector::front() call because we get an empty vector. I guess this is just a compile-time test?

[asuessenbach]

Thanks for providing some test code. Added it to the DeviceFunctions test.

And yes, it's a pure compile test, not meant for actually running it.