From a77cc0cb35455d12a84ccde1e7457345448a375c Mon Sep 17 00:00:00 2001
From: Matthias Melcher <github@matthiasm.com>
Date: Mon, 4 Nov 2024 22:35:43 +0100
Subject: [PATCH] MacOS version check using try_compile: #1103

This change will work as well when cross-compiling.
---
 CMake/macOSMaxAllowed.c | 12 +++++-------
 CMake/setup.cmake       | 30 +++++++++++++++---------------
 2 files changed, 20 insertions(+), 22 deletions(-)

diff --git a/CMake/macOSMaxAllowed.c b/CMake/macOSMaxAllowed.c
index 625bcb6af..93fff3c3d 100644
--- a/CMake/macOSMaxAllowed.c
+++ b/CMake/macOSMaxAllowed.c
@@ -1,8 +1,6 @@
-#include <Availability.h>
-#include <stdio.h>
 
-int main(int argc, char **argv) {
-  unsigned int ver = __MAC_OS_X_VERSION_MAX_ALLOWED;
-  printf("%d.%d.%d", ver/10000, (ver/100)%100, ver%100);
-  return 0;
-}
+#include <AvailabilityMacros.h>
+#if __MAC_OS_X_VERSION_MAX_ALLOWED < SDK_VERSION_CHECK
+#error __MAC_OS_X_VERSION_MAX_ALLOWED < SDK_VERSION_CHECK
+#endif
+int main(int, char**) { return 0; }
diff --git a/CMake/setup.cmake b/CMake/setup.cmake
index 8c06f2782..fa9534c0a 100644
--- a/CMake/setup.cmake
+++ b/CMake/setup.cmake
@@ -111,25 +111,23 @@ if(CMAKE_GENERATOR MATCHES "Xcode")
 endif()
 
 if(APPLE)
+  # Check if the __MAC_OS_X_VERSION_MAX_ALLOWED compile time macro is at least
+  # the version encoded in SDK_VERSION and return TRUE or FALSE in RESULT.
+  macro(CHECK_OSX_MAX_ALLOWED SDK_VERSION RESULT)
+    try_compile(LOCAL_RESULT
+      ${CMAKE_BINARY_DIR}/CMakeTmpDup
+      SOURCES ${CMAKE_CURRENT_SOURCE_DIR}/CMake/macOSMaxAllowed.c
+      COMPILE_DEFINITIONS -DSDK_VERSION_CHECK=${SDK_VERSION}
+    )
+    set(${RESULT} ${LOCAL_RESULT})
+  endmacro()
+  # APPLE macOS setup
   set(HAVE_STRCASECMP 1)
   set(HAVE_DIRENT_H 1)
   set(HAVE_SNPRINTF 1)
   set(HAVE_VSNPRINTF 1)
   set(HAVE_SCANDIR 1)
   set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -Wno-deprecated")
-  # Retrieve the value of the macOS compile-time macro
-  # __MAC_OS_X_VERSION_MAX_ALLOWED. This is needed to decide which
-  # frameworks must be linked later.
-  try_run(
-    RUN_RESULT COMPILE_RESULT
-    SOURCES ${CMAKE_CURRENT_SOURCE_DIR}/CMake/macOSMaxAllowed.c
-    RUN_OUTPUT_VARIABLE MAC_OS_X_VERSION_MAX_ALLOWED
-  )
-  if (NOT COMPILE_RESULT)
-    set(MAC_OS_X_VERSION_MAX_ALLOWED ${CURRENT_OSX_VERSION})
-  endif()
-  fl_debug_var(CMAKE_OSX_DEPLOYMENT_TARGET)
-  fl_debug_var(MAC_OS_X_VERSION_MAX_ALLOWED)
   if(FLTK_BACKEND_X11)
     if(NOT(${CMAKE_SYSTEM_VERSION} VERSION_LESS 17.0.0)) # a.k.a. macOS version ≥ 10.13
       set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -D_LIBCPP_HAS_THREAD_API_PTHREAD")
@@ -137,10 +135,12 @@ if(APPLE)
   else()
     set(FLTK_COCOA_FRAMEWORKS "-framework Cocoa")
     if (NOT (CMAKE_OSX_ARCHITECTURES STREQUAL "ppc" OR CMAKE_OSX_ARCHITECTURES STREQUAL "i386"))
-      if(${MAC_OS_X_VERSION_MAX_ALLOWED} VERSION_GREATER_EQUAL 11.0)
+      CHECK_OSX_MAX_ALLOWED(110000 SDK_AVAILABLE) # at least SDK 11.0.0 ?
+      if (SDK_AVAILABLE)
         list(APPEND FLTK_COCOA_FRAMEWORKS "-weak_framework UniformTypeIdentifiers")
       endif()
-      if(${MAC_OS_X_VERSION_MAX_ALLOWED} VERSION_GREATER_EQUAL 15.0)
+      CHECK_OSX_MAX_ALLOWED(150000 SDK_AVAILABLE) # at least SDK 15.0.0 ?
+      if (SDK_AVAILABLE)
         list(APPEND FLTK_COCOA_FRAMEWORKS "-weak_framework ScreenCaptureKit")
       endif()
     endif()