From 78e29ea83d0ca2a50be3d981e0c1c6b176e69222 Mon Sep 17 00:00:00 2001
From: Kris Thielemans <k.thielemans@ucl.ac.uk>
Date: Sun, 28 Apr 2024 20:17:46 +0100
Subject: [PATCH 1/2] [GHA] remove explicit setting of xcode version

Fixes #1411
---
 .github/workflows/build-test.yml | 3 ---
 1 file changed, 3 deletions(-)

diff --git a/.github/workflows/build-test.yml b/.github/workflows/build-test.yml
index 7d1e65357..8c0cb93cb 100644
--- a/.github/workflows/build-test.yml
+++ b/.github/workflows/build-test.yml
@@ -162,9 +162,6 @@ jobs:
             CXX=${CXX}-${{ matrix.compiler_version }}            
           fi
           if test 'XX${{ matrix.os }}' = 'XXmacOS-latest'; then
-            # need to force XCode version for the moment due to a linker bug
-            # see https://github.com/UCL/STIR/issues/1103
-            echo DEVELOPER_DIR="/Applications/Xcode_14.1.app/Contents/Developer" >> $GITHUB_ENV
             if test 'XX${{ matrix.compiler }}' = 'XXclang'; then
               brew install llvm@${{ matrix.compiler_version }}
               if test XX${HOMEBREW_PREFIX} = XX; then

From 5ccb4409cc14230953bb8d50cb2ceb7bed7250e7 Mon Sep 17 00:00:00 2001
From: Kris Thielemans <k.thielemans@ucl.ac.uk>
Date: Tue, 30 Apr 2024 22:24:40 +0100
Subject: [PATCH 2/2] update Byte Order compile-time checks

previous version failed on macos-14-arm64.
We have a very fragile list of checks. Presumably, CMake does a lot better,
so use CMAKE_CXX_BYTE_ORDER in ByteOrderDefine (via config.h)
---
 documentation/release_6.1.htm      |  5 +++++
 src/CMakeLists.txt                 | 12 ++++++++++++
 src/cmake/STIRConfig.h.in          |  4 ++++
 src/include/stir/ByteOrderDefine.h | 12 ++++++++----
 4 files changed, 29 insertions(+), 4 deletions(-)

diff --git a/documentation/release_6.1.htm b/documentation/release_6.1.htm
index 562fa25c9..1bb9ab02d 100644
--- a/documentation/release_6.1.htm
+++ b/documentation/release_6.1.htm
@@ -70,6 +70,11 @@ <h3>Bug fixes</h3>
   <li>The Relative Difference Prior gave incorrect results, probably since switching to C++-14 in version 6.0, although we are not sure.
     See <a href=https://github.com/UCL/STIR/pull/1410>PR #1410</a> and associated <a href=https://github.com/UCL/STIR/pull/1409>issue #1409</a>.
   </li>
+  <li>
+      Our checks for determining system byte-order were out-of-date and in particular did not work on MacOS 14 on ARM.
+      We now use CMake's <code>CMAKE_CXX_BYTE_ORDER</code> (available since CMake 3.20).
+      See <a href=https://github.com/UCL/STIR/pull/1412>PR #1412</a>.
+  </li>
 </ul>
 
 <h3>Known problems</h3>
diff --git a/src/CMakeLists.txt b/src/CMakeLists.txt
index 4101bf85d..7a731c2e6 100644
--- a/src/CMakeLists.txt
+++ b/src/CMakeLists.txt
@@ -192,6 +192,18 @@ else()
     set(STIR_USE_BOOST_SHARED_PTR ON)
 endif()
 
+# Byte order
+if (CMAKE_VERSION VERSION_GREATER_EQUAL 3.20)
+    # Use CMake to find byte order of target system.
+    # We create some variables that are then used in config.h.in
+    if (CMAKE_CXX_BYTE_ORDER STREQUAL "BIG_ENDIAN")
+        set(BIG_ENDIAN_BYTE_ORDER_FROM_CMAKE TRUE)
+        message(STATUS "CMake detected a big_endian system")
+    elseif (CMAKE_CXX_BYTE_ORDER STREQUAL "LITTLE_ENDIAN")
+        set(LITTLE_ENDIAN_BYTE_ORDER_FROM_CMAKE TRUE)
+        message(STATUS "CMake detected a little_endian system")
+    endif()
+endif()
 
 #### Create stir/config.h
 
diff --git a/src/cmake/STIRConfig.h.in b/src/cmake/STIRConfig.h.in
index 515f021e5..ecb62fa4a 100644
--- a/src/cmake/STIRConfig.h.in
+++ b/src/cmake/STIRConfig.h.in
@@ -52,6 +52,10 @@ namespace stir {
 
 #include "boost/config.hpp"
 
+// 2 variables set via CMake
+#cmakedefine BIG_ENDIAN_BYTE_ORDER_FROM_CMAKE
+#cmakedefine LITTLE_ENDIAN_BYTE_ORDER_FROM_CMAKE
+
 #cmakedefine HAVE_ECAT
 #ifdef HAVE_ECAT
 #define HAVE_LLN_MATRIX
diff --git a/src/include/stir/ByteOrderDefine.h b/src/include/stir/ByteOrderDefine.h
index de909de3b..456502afa 100644
--- a/src/include/stir/ByteOrderDefine.h
+++ b/src/include/stir/ByteOrderDefine.h
@@ -23,10 +23,14 @@
 START_NAMESPACE_STIR
 
 // currently checked by asserts()
-#if !defined(__alpha) && (!defined(_WIN32) || defined(_M_PPC) || defined(_M_MPPC)) && !defined(__i386__) && !defined(__i486__)   \
-        && !defined(__i586__) && !defined(__i686__) && !defined(__i786__) && !defined(__i886__) && !defined(__k6__)              \
-        && !defined(__athlon__) && !defined(__x86_64__) && !defined(__k6__)                                                      \
-    || (defined(__MSL__) && !defined(__LITTLE_ENDIAN))
+// partially from https://stackoverflow.com/a/27054190
+#if defined(BIG_ENDIAN_BYTE_ORDER_FROM_CMAKE)         /* variable set via CMake in stir/config.h */                              \
+    || (!defined(LITTLE_ENDIAN_BYTE_ORDER_FROM_CMAKE) /* variable set via CMake in stir/config.h */                              \
+        && ((!defined(__alpha) && (!defined(_WIN32) || defined(_M_PPC) || defined(_M_MPPC)) && !defined(__i386__)                \
+                 && !defined(__i486__) && !defined(__i586__) && !defined(__i686__) && !defined(__i786__) && !defined(__i886__)   \
+                 && !defined(__k6__) && !defined(__athlon__) && !defined(__x86_64__) && !defined(__k6__))                         \
+             || (defined(__MSL__) && !defined(__LITTLE_ENDIAN)) || (defined(__BYTE_ORDER) && __BYTE_ORDER == __BIG_ENDIAN)       \
+             || (defined(__BYTE_ORDER__) && (__BYTE_ORDER__ == __ORDER_BIG_ENDIAN__) /* gcc */) || defined(__BIG_ENDIAN__)))
 #  define STIRIsNativeByteOrderBigEndian 1
 #  define STIRIsNativeByteOrderLittleEndian 0
 #else