add feature JSON output

CMakeLists.txt

@@ -17,11 +17,12 @@ include(CheckSourceRuns)
 
 # --- compiler checks
 
-foreach(i IN ITEMS f03abstract f03charalloc f03ieee f03utf8 f03selectType
-  f08contig f08execute f08kind
-  f18abstract f18assumed_rank f18prop f18random f2018rank
-  f2023rank_integer f2023ternary f2023tokenize f2023real16)
+set(f2003features f03abstract f03charalloc f03ieee f03utf8 f03selectType)
+set(f2008features f08contig f08execute f08kind)
+set(f2018features f18abstract f18assumed_rank f18prop f18random f2018rank)
+set(f2023features f2023rank_integer f2023ternary f2023tokenize f2023real16)
 
+foreach(i IN LISTS f2003features f2008features f2018features f2023features)
   include(cmake/${i}.cmake)
 endforeach()
 
@@ -40,3 +41,5 @@ foreach(a IN ITEMS git system)
 endforeach()
 
 file(GENERATE OUTPUT .gitignore CONTENT "*")
+
+include(cmake/features.cmake)

cmake/f2018rank.cmake

@@ -0,0 +1,9 @@
+set(CMAKE_TRY_COMPILE_TARGET_TYPE STATIC_LIBRARY)
+
+check_source_compiles(Fortran "subroutine poly(A)
+  intrinsic :: rank
+  real, intent(in) :: A(:)
+  real :: B(rank(A))
+  B = A
+end subroutine"
+f2018rank)

cmake/features.cmake

@@ -0,0 +1,29 @@
+set(j "{}")
+
+foreach(s IN LISTS f2003features f2008features f2018features f2023features)
+  foreach(f IN LISTS s)
+    if(${f})
+      set(hasf true)
+    else()
+      set(hasf false)
+    endif()
+
+    string(JSON j SET ${j} ${f} ${hasf})
+  endforeach()
+endforeach()
+
+
+string(JSON j SET ${j} compiler "{}")
+string(JSON j SET ${j} compiler vendor \"${CMAKE_Fortran_COMPILER_ID}\")
+string(JSON j SET ${j} compiler version \"${CMAKE_Fortran_COMPILER_VERSION}\")
+string(JSON j SET ${j} compiler system \"${CMAKE_SYSTEM_NAME}\")
+string(JSON j SET ${j} compiler system_version \"${CMAKE_SYSTEM_VERSION}\")
+string(JSON j SET ${j} compiler target \"${CMAKE_SYSTEM_PROCESSOR}\")
+string(JSON j SET ${j} compiler flags \"${CMAKE_Fortran_FLAGS}\")
+string(JSON j SET ${j} compiler sysroot \"${CMAKE_OSX_SYSROOT}\")
+
+set(feature_file ${CMAKE_CURRENT_BINARY_DIR}/features.json)
+
+file(WRITE ${feature_file} ${j})
+
+message(STATUS "See ${feature_file} for features enabled")