On Darwin, add "darwin.h" and "darwin.mm" files into the arch target for using darwin code via ObjectiveC++, to use System API for Temporary Directory location instead of looking up an env var. This matches Windows behavior, and

   is required for stricter containerized temp directory in macOS 26 for sandbox processes.

Closes #3705

(Internal change: 2392207)

Author: dgovil

pxr/base/arch/CMakeLists.txt

@@ -5,16 +5,23 @@ set(PXR_PREFIX pxr/base)
 set(PXR_PACKAGE arch)
 
 if(NOT EMSCRIPTEN)
-    set(PLATFORM_LIBS ${M_LIB})
+    set(ARCH_PLATFORM_LIBS ${M_LIB})
+    set(ARCH_PLATFORM_HEADERS "")
+    set(ARCH_PLATFORM_CPPFILES "")
 endif()
+
 if(WIN32)
-    set(PLATFORM_LIBS Ws2_32.lib Dbghelp.lib ${PLATFORM_LIBS})
+    set(ARCH_PLATFORM_LIBS Ws2_32.lib Dbghelp.lib ${ARCH_PLATFORM_LIBS})
+elseif (APPLE)
+    set(ARCH_PLATFORM_HEADERS darwin.h)
+    set(ARCH_PLATFORM_CPPFILES darwin.mm)
+    set(ARCH_PLATFORM_LIBS "-framework Foundation" ${ARCH_PLATFORM_LIBS})
 endif()
 
 pxr_library(arch
     LIBRARIES
         ${CMAKE_DL_LIBS}
-        ${PLATFORM_LIBS}
+        ${ARCH_PLATFORM_LIBS}
 
     PUBLIC_CLASSES
         align
@@ -53,10 +60,12 @@ pxr_library(arch
     PRIVATE_HEADERS
         testArchAbi.h
         testArchUtil.h
+        ${ARCH_PLATFORM_HEADERS}
 
     CPPFILES
         assumptions.cpp
         initConfig.cpp
+        ${ARCH_PLATFORM_CPPFILES}
 
     DOXYGEN_FILES
         overview.dox

pxr/base/arch/darwin.h

@@ -0,0 +1,16 @@
+//
+// Copyright 2025 Apple
+//
+// Licensed under the terms set forth in the LICENSE.txt file available at
+// https://openusd.org/license.
+//
+#ifndef PXR_ARCH_DARWIN_H
+#define PXR_ARCH_DARWIN_H
+#include "pxr/pxr.h"
+
+PXR_NAMESPACE_OPEN_SCOPE
+
+const char* Arch_DarwinGetTemporaryDirectory();
+
+PXR_NAMESPACE_CLOSE_SCOPE
+#endif // PXR_ARCH_DARWIN_H

pxr/base/arch/darwin.mm

@@ -0,0 +1,18 @@
+//
+// Copyright 2025 Apple
+//
+// Licensed under the terms set forth in the LICENSE.txt file available at
+// https://openusd.org/license.
+//
+
+#include "pxr/base/arch/darwin.h"
+#import <Foundation/Foundation.h>
+
+PXR_NAMESPACE_OPEN_SCOPE
+
+
+const char* Arch_DarwinGetTemporaryDirectory() {
+    return [NSTemporaryDirectory() UTF8String];
+}
+
+PXR_NAMESPACE_CLOSE_SCOPE

pxr/base/arch/fileSystem.cpp

@@ -41,6 +41,10 @@
 #include <unistd.h>
 #endif
 
+#if defined(ARCH_OS_DARWIN)
+#include "pxr/base/arch/darwin.h"
+#endif
+
 PXR_NAMESPACE_OPEN_SCOPE
 
 using std::pair;
@@ -727,6 +731,9 @@ Arch_InitTmpDir()
     // Strip the trailing slash
     tmpPath[sizeOfPath-1] = 0;
     _TmpDir = _strdup(ArchWindowsUtf16ToUtf8(tmpPath).c_str());
+#elif defined(ARCH_OS_DARWIN)
+    // On Apple platforms, we use the system APIs to get the designated temp directory
+    _TmpDir = strdup(Arch_DarwinGetTemporaryDirectory());
 #else
     const std::string tmpdir = ArchGetEnv("TMPDIR");
     if (!tmpdir.empty()) {
@@ -735,9 +742,7 @@ Arch_InitTmpDir()
         // set, the following call will leak a string.
         _TmpDir = strdup(tmpdir.c_str());
     } else {
-#if defined(ARCH_OS_DARWIN)
-        _TmpDir = "/tmp";
-#elif defined(ARCH_OS_WASM_VM)
+#if defined(ARCH_OS_WASM_VM)
         // Note: WASM will always create /tmp as part of its in memory
         // filesystem. All data will be lost when the VM is shut down.
         _TmpDir = "/tmp";