Fix compilation issues when building USD using the C++20 standard

pxr/imaging/hd/instanceRegistry.h

@@ -177,7 +177,7 @@ class HdInstanceRegistry {
 private:
     template <typename T>
     static bool _IsUnique(std::shared_ptr<T> const &value) {
-        return value.unique();
+        return value.use_count() == 1;
     }
 
     typename InstanceType::Dictionary _dictionary;

pxr/imaging/hdSt/resourceRegistry.cpp

@@ -551,8 +551,9 @@ HdStResourceRegistry::GarbageCollectDispatchBuffers()
     _dispatchBufferRegistry.erase(
         std::remove_if(
             _dispatchBufferRegistry.begin(), _dispatchBufferRegistry.end(),
-            std::bind(&HdStDispatchBufferSharedPtr::unique,
-                      std::placeholders::_1)),
+            [](const HdStDispatchBufferSharedPtr& ptr) {
+                return ptr.use_count() == 1;
+            }),
         _dispatchBufferRegistry.end());
 }
 
@@ -564,8 +565,9 @@ HdStResourceRegistry::GarbageCollectBufferResources()
     _bufferResourceRegistry.erase(
         std::remove_if(
             _bufferResourceRegistry.begin(), _bufferResourceRegistry.end(),
-            std::bind(&HdStBufferResourceSharedPtr::unique,
-                      std::placeholders::_1)),
+            [](const HdStBufferResourceSharedPtr& ptr) {
+                return ptr.use_count() == 1;
+            }),
         _bufferResourceRegistry.end());
 }
 

pxr/imaging/hdSt/samplerObjectRegistry.cpp

@@ -129,13 +129,13 @@ HdSt_SamplerObjectRegistry::GarbageCollect()
     size_t last = _samplerObjects.size();
 
     for (size_t i = 0; i < last; i++) {
-        if (_samplerObjects[i].unique()) {
+        if (_samplerObjects[i].use_count() == 1) {
             while(true) {
                 last--;
                 if (i == last) {
                     break;
                 }
-                if (!_samplerObjects[last].unique()) {
+                if (_samplerObjects[last].use_count() != 1) {
                     _samplerObjects[i] = _samplerObjects[last];
                     break;
                 }

pxr/imaging/hio/stb/stb_image.h

@@ -4626,7 +4626,7 @@ static int stbi__check_png_header(stbi__context *s)
    return 1;
 }
 
-typedef struct
+typedef struct stbi__png_type
 {
    stbi__context *s;
    stbi_uc *idata, *expanded, *out;

pxr/imaging/hio/stb/stb_image.patch

@@ -1,5 +1,5 @@
---- original/stb_image.h	2024-05-21 15:30:18.887733957 -0700
-+++ stb_image.h	2024-05-21 15:17:49.371401403 -0700
+--- original/stb_image.h	2024-12-09 08:40:54
++++ stb_image.h	2024-12-09 08:41:15
 @@ -490,14 +490,14 @@
  STBIDEF void     stbi_image_free      (void *retval_from_stbi_load);
 
@@ -28,7 +28,13 @@
  static int      stbi__png_is16(stbi__context *s);
  #endif
 
-@@ -4631,6 +4631,7 @@
+@@ -4626,11 +4626,12 @@
+    return 1;
+ }
+
+-typedef struct
++typedef struct stbi__png_type
+ {
     stbi__context *s;
     stbi_uc *idata, *expanded, *out;
     int depth;

pxr/usd/pcp/primIndex_Graph.cpp

@@ -613,7 +613,7 @@ PcpPrimIndex_Graph::_InsertChildInStrengthOrder(
 void 
 PcpPrimIndex_Graph::_DetachSharedNodePool()
 {
-    if (!_nodes.unique()) {
+    if (_nodes.use_count() != 1) {
         TRACE_FUNCTION();
         TfAutoMallocTag tag("_DetachSharedNodePool");
         _nodes = std::make_shared<_NodePool>(*_nodes);
@@ -623,7 +623,7 @@ PcpPrimIndex_Graph::_DetachSharedNodePool()
 void 
 PcpPrimIndex_Graph::_DetachSharedNodePoolForNewNodes(size_t numAddedNodes)
 {
-    if (!_nodes.unique()) {
+    if (_nodes.use_count() != 1) {
         TRACE_FUNCTION();
         TfAutoMallocTag tag("_DetachSharedNodePoolForNewNodes");
         // Create a new copy, but with some extra capacity since we are adding