Functions: support optional outputs in multi-function

Sometimes not all outputs of a multi-function are required by the
caller. In those cases it would be a waste of compute resources
to calculate the unused values anyway. Now, the caller of a
multi-function can specify when a specific output is not used.
The called function can check if an output is unused and may
ignore it. Multi-functions can still computed unused outputs as
before if they don't want to check if a specific output is unused.

The multi-function procedure system has been updated to support
ignored outputs in call instructions. An ignored output just has no
variable assigned to it.

The field system has been updated to generate a multi-function
procedure where unused outputs are ignored.

1 files changed, 11 insertions, 0 deletions

diff --git a/source/blender/blenlib/BLI_resource_scope.hh b/source/blender/blenlib/BLI_resource_scope.hh
index 6a98c2dcc1c..c3c0af4af50 100644
--- a/source/blender/blenlib/BLI_resource_scope.hh
+++ b/source/blender/blenlib/BLI_resource_scope.hh
@@ -137,6 +137,17 @@ class ResourceScope : NonCopyable, NonMovable {
   }
 
   /**
+   * The passed in function will be called when the scope is destructed.
+   */
+  template<typename Func> void add_destruct_call(Func func, const char *name)
+  {
+    void *buffer = m_allocator.allocate(sizeof(func), alignof(func));
+    new (buffer) Func(std::move(func));
+    this->add(
+        buffer, [](void *data) { (*(Func *)data)(); }, name);
+  }
+
+  /**
    * Returns a reference to a linear allocator that is owned by the ResourcesCollector. Memory
    * allocated through this allocator will be freed when the collector is destructed.
    */