From fcf6a840cbf7cf046403f5314561dee3f235b9c7 Mon Sep 17 00:00:00 2001
From: Oliver Thomson Brown <8394906+otbrown@users.noreply.github.com>
Date: Wed, 11 Jun 2025 17:24:14 +0100
Subject: [PATCH 1/4] Promoted variables set in compile_option CMake function
 to parent scope, which ensures correct values are generated in the header
 file.

---
 CMakeLists.txt | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 1080c55fc..16ea69e83 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -79,7 +79,7 @@ else()
   set(MULTI_LIB_HEADERS 0)
   function(compile_option VAR VALUE)
     target_compile_definitions(QuEST PRIVATE ${VAR}=${VALUE})
-    set(${VAR} ${VALUE})
+    set(${VAR} ${VALUE} PARENT_SCOPE)
   endfunction()
 endif()
 

From 61cd1dced475b5c756bed06815e92bba5805d36c Mon Sep 17 00:00:00 2001
From: Oliver Thomson Brown <otbrown@users.noreply.github.com>
Date: Fri, 13 Jun 2025 14:50:41 +0100
Subject: [PATCH 2/4] Separated compilation configuration defines into config.h

---
 CMakeLists.txt                        |  7 ++++++-
 quest/include/CMakeLists.txt          |  2 +-
 quest/include/config.h.in             | 15 +++++++++++++++
 quest/include/{quest.h.in => quest.h} | 12 ++----------
 4 files changed, 24 insertions(+), 12 deletions(-)
 create mode 100644 quest/include/config.h.in
 rename quest/include/{quest.h.in => quest.h} (87%)

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 16ea69e83..d10721947 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -576,13 +576,18 @@ install(FILES
         DESTINATION "${QuEST_INSTALL_CONFIGDIR}"
 )
 
-install(FILES "${CMAKE_CURRENT_BINARY_DIR}/include/quest.h"
+install(FILES "${CMAKE_CURRENT_SOURCE_DIR}/quest/include/quest.h"
         DESTINATION "${CMAKE_INSTALL_INCLUDEDIR}"
 )
 
+install(FILES "${CMAKE_CURRENT_BINARY_DIR}/include/quest/include/config.h"
+        DESTINATION "${CMAKE_INSTALL_INCLUDEDIR}/quest/include"
+)
+
 install(DIRECTORY "${CMAKE_CURRENT_SOURCE_DIR}/quest/include"
         DESTINATION "${CMAKE_INSTALL_INCLUDEDIR}/quest"
         FILES_MATCHING PATTERN "*.h"
+        PATTERN "quest.h" EXCLUDE
 )
 
 install(EXPORT QuESTTargets
diff --git a/quest/include/CMakeLists.txt b/quest/include/CMakeLists.txt
index 86a542dc5..bf0d1cd09 100644
--- a/quest/include/CMakeLists.txt
+++ b/quest/include/CMakeLists.txt
@@ -2,4 +2,4 @@
 # @author Erich Essmann
 # @author Luc Jaulmes (using config file)
 
-configure_file(quest.h.in "${CMAKE_BINARY_DIR}/include/quest.h" @ONLY)
+configure_file(config.h.in "${CMAKE_BINARY_DIR}/include/quest/include/config.h" @ONLY)
diff --git a/quest/include/config.h.in b/quest/include/config.h.in
new file mode 100644
index 000000000..4c832a76e
--- /dev/null
+++ b/quest/include/config.h.in
@@ -0,0 +1,15 @@
+#ifndef CONFIG_H
+#define CONFIG_H
+
+
+// bind compile settings to installed exec
+#if !@MULTI_LIB_HEADERS@
+#cmakedefine FLOAT_PRECISION @FLOAT_PRECISION@
+#cmakedefine01 COMPILE_MPI
+#cmakedefine01 COMPILE_OPENMP
+#cmakedefine01 COMPILE_CUDA
+#cmakedefine01 COMPILE_CUQUANTUM
+#endif
+
+
+#endif
\ No newline at end of file
diff --git a/quest/include/quest.h.in b/quest/include/quest.h
similarity index 87%
rename from quest/include/quest.h.in
rename to quest/include/quest.h
index 4ba420478..fcc49ab76 100644
--- a/quest/include/quest.h.in
+++ b/quest/include/quest.h
@@ -31,20 +31,12 @@
 #define QUEST_H
 
 
-// bind compile settings to installed exec
-#if !@MULTI_LIB_HEADERS@
-#cmakedefine FLOAT_PRECISION @FLOAT_PRECISION@
-#cmakedefine01 COMPILE_MPI
-#cmakedefine01 COMPILE_OPENMP
-#cmakedefine01 COMPILE_CUDA
-#cmakedefine01 COMPILE_CUQUANTUM
-#endif
-
-
 // include version first so it is accessible to 
 // debuggers in case a subsequent include fails
 #include "quest/include/version.h"
 
+#include "quest/include/config.h"
+
 // include before API headers since it validates
 // preprocessor configuration, and affirms macro
 // preconditions assumed by subsequent header

From 85f8ed06bb0e4eaa7ec24182f909f65925f44f19 Mon Sep 17 00:00:00 2001
From: Oliver Thomson Brown <otbrown@users.noreply.github.com>
Date: Fri, 13 Jun 2025 15:34:03 +0100
Subject: [PATCH 3/4] Added guards to check at least one of the required
 compiler macros is undefined as proposed by @TysonRayJones

---
 quest/include/config.h.in | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/quest/include/config.h.in b/quest/include/config.h.in
index 4c832a76e..8326259b6 100644
--- a/quest/include/config.h.in
+++ b/quest/include/config.h.in
@@ -1,6 +1,12 @@
 #ifndef CONFIG_H
 #define CONFIG_H
 
+// be warned, the below is sensitive to whitespace after the slash
+#if !defined(FLOAT_PRECISION)\
+    || !defined(COMPILE_MPI)\
+    || !defined(COMPILE_OPENMP)\
+    || !defined(COMPILE_CUDA)\
+    || !defined(COMPILE_CUQUANTUM)
 
 // bind compile settings to installed exec
 #if !@MULTI_LIB_HEADERS@
@@ -11,5 +17,6 @@
 #cmakedefine01 COMPILE_CUQUANTUM
 #endif
 
+#endif
 
 #endif
\ No newline at end of file

From 1f1e70288a57beca091f8f84bc55eefdad037ac4 Mon Sep 17 00:00:00 2001
From: Oliver Thomson Brown <otbrown@users.noreply.github.com>
Date: Fri, 13 Jun 2025 15:48:50 +0100
Subject: [PATCH 4/4] modes.h: removed guards which prevented COMPILE macros
 from being defined, as proposed by @TysonRayJones

---
 quest/include/modes.h | 21 +--------------------
 1 file changed, 1 insertion(+), 20 deletions(-)

diff --git a/quest/include/modes.h b/quest/include/modes.h
index b90797acd..667a3f053 100644
--- a/quest/include/modes.h
+++ b/quest/include/modes.h
@@ -15,27 +15,8 @@
 
 
 
-// ensure all mode flags are defined
-
-#ifndef COMPILE_MPI
-    #error "Compiler must define COMPILE_MPI"
-#endif
-
-#ifndef COMPILE_OPENMP
-    #error "Compiler must define COMPILE_OPENMP"
-#endif
-
-#ifndef COMPILE_CUDA
-    #error "Compiler must define COMPILE_CUDA"
-#endif
-
-#ifndef COMPILE_CUQUANTUM
-    #error "Compiler must define COMPILE_CUQUANTUM"
-#endif
-
-
-
 // ensure all mode flags are valid values
+// undefined allowed as undefined == 0 in C/C++ standards
 
 #if ! (COMPILE_MPI == 0 || COMPILE_MPI == 1)
     #error "Macro COMPILE_MPI must have value 0 or 1"