From 155f1bf174e2b87a4de721e936f8b6ab141079fb Mon Sep 17 00:00:00 2001
From: Sergey Fedorov <vital.had@gmail.com>
Date: Tue, 16 May 2023 12:56:42 +0800
Subject: [PATCH] Use posix compat code for old macOS without libdispatch
 (#1409)

See: https://github.com/AcademySoftwareFoundation/openexr/issues/1405

Signed-off-by: Sergey Fedorov <vital.had@gmail.com>
---
 src/lib/IlmThread/IlmThreadSemaphore.h        | 36 ++++++++++---------
 src/lib/IlmThread/IlmThreadSemaphoreOSX.cpp   |  5 +++
 .../IlmThreadSemaphorePosixCompat.cpp         | 11 ++++--
 3 files changed, 34 insertions(+), 18 deletions(-)

diff --git a/src/lib/IlmThread/IlmThreadSemaphore.h b/src/lib/IlmThread/IlmThreadSemaphore.h
index 576968aa65..fc75de3bac 100644
--- a/src/lib/IlmThread/IlmThreadSemaphore.h
+++ b/src/lib/IlmThread/IlmThreadSemaphore.h
@@ -18,21 +18,25 @@
 #include "IlmThreadConfig.h"
 #include "IlmThreadNamespace.h"
 
+#if defined(__APPLE__)
+#   include <AvailabilityMacros.h>
+#endif
+
 #if ILMTHREAD_THREADING_ENABLED
-#   if ILMTHREAD_HAVE_POSIX_SEMAPHORES
-#      include <semaphore.h>
-#   elif defined(__APPLE__)
-#      include <dispatch/dispatch.h>
-#   elif (defined (_WIN32) || defined (_WIN64))
-#      ifdef NOMINMAX
-#         undef NOMINMAX
-#      endif
-#      define NOMINMAX
-#      include <windows.h>
-#   else
-#      include <mutex>
-#      include <condition_variable>
-#   endif
+#    if ILMTHREAD_HAVE_POSIX_SEMAPHORES
+#        include <semaphore.h>
+#    elif defined(__APPLE__) && __MAC_OS_X_VERSION_MIN_REQUIRED > 1050 && !defined(__ppc__)
+#        include <dispatch/dispatch.h>
+#    elif (defined(_WIN32) || defined(_WIN64))
+#        ifdef NOMINMAX
+#            undef NOMINMAX
+#        endif
+#        define NOMINMAX
+#        include <windows.h>
+#    else
+#        include <condition_variable>
+#        include <mutex>
+#    endif
 #endif
 
 ILMTHREAD_INTERNAL_NAMESPACE_HEADER_ENTER
@@ -56,8 +60,8 @@ class ILMTHREAD_EXPORT_TYPE Semaphore
 
 	mutable sem_t _semaphore;
 
-#elif defined(__APPLE__)
-	mutable dispatch_semaphore_t _semaphore;
+#elif defined(__APPLE__) && __MAC_OS_X_VERSION_MIN_REQUIRED > 1050 && !defined(__ppc__)
+    mutable dispatch_semaphore_t _semaphore;
 
 #elif (defined (_WIN32) || defined (_WIN64))
 
diff --git a/src/lib/IlmThread/IlmThreadSemaphoreOSX.cpp b/src/lib/IlmThread/IlmThreadSemaphoreOSX.cpp
index 0ab0b37cf2..3c49578d4b 100644
--- a/src/lib/IlmThread/IlmThreadSemaphoreOSX.cpp
+++ b/src/lib/IlmThread/IlmThreadSemaphoreOSX.cpp
@@ -11,6 +11,10 @@
 //-----------------------------------------------------------------------------
 
 #if defined(__APPLE__) && !ILMTHREAD_HAVE_POSIX_SEMAPHORES
+#    include <AvailabilityMacros.h>
+
+// No libdispatch prior to 10.6, and no support for it on any ppc.
+#if __MAC_OS_X_VERSION_MIN_REQUIRED > 1050 && !defined(__ppc__)
 
 #include "IlmThreadSemaphore.h"
 #include "Iex.h"
@@ -66,4 +70,5 @@ Semaphore::value () const
 
 ILMTHREAD_INTERNAL_NAMESPACE_SOURCE_EXIT
 
+#    endif
 #endif
diff --git a/src/lib/IlmThread/IlmThreadSemaphorePosixCompat.cpp b/src/lib/IlmThread/IlmThreadSemaphorePosixCompat.cpp
index a2d562d636..fda6a5b26f 100644
--- a/src/lib/IlmThread/IlmThreadSemaphorePosixCompat.cpp
+++ b/src/lib/IlmThread/IlmThreadSemaphorePosixCompat.cpp
@@ -12,10 +12,17 @@
 
 #include "IlmThreadConfig.h"
 
+#if defined(__APPLE__)
+#    include <AvailabilityMacros.h>
+#endif
+
+// Use this code as a fallback for macOS versions without libdispatch.
 #if ILMTHREAD_THREADING_ENABLED
-#if ( !(ILMTHREAD_HAVE_POSIX_SEMAPHORES) && !defined (__APPLE__) && !defined (_WIN32) && !defined (_WIN64) )
+#    if (!(ILMTHREAD_HAVE_POSIX_SEMAPHORES) && !defined(_WIN32) && !defined(_WIN64) && \
+        (!defined(__APPLE__) || (defined(__APPLE__) && \
+        (__MAC_OS_X_VERSION_MIN_REQUIRED < 1060 || defined(__ppc__)))))
 
-#include "IlmThreadSemaphore.h"
+#    include "IlmThreadSemaphore.h"
 
 ILMTHREAD_INTERNAL_NAMESPACE_SOURCE_ENTER