add _R16P_SUPPORTED auto detection

Author: lettleli

src/lib/CMakeLists.txt

@@ -22,6 +22,59 @@ target_include_directories(${LIB}
         $<BUILD_INTERFACE:${CMAKE_Fortran_MODULE_DIRECTORY}>
 )
 
+function(check_fortran_source_runs code resultVar)
+    cmake_parse_arguments(PARSE_ARGV 2 check "" "SRC_EXT" "FAIL_REGEX")
+    # message("${code}")
+    # message("${check_SRC_EXT}")
+    # message("${check_FAIL_REGEX}")
+    if(DEFINED call_SRC_EXT)
+        set(ext "${check_SRC_EXT}")
+    else()
+        set(ext "f90")
+    endif()
+    file(WRITE ${CMAKE_CURRENT_BINARY_DIR}/CMakeFiles/check_fortran_source_runs.${ext} "${code}")
+    try_run(run_result compile_result
+        ${CMAKE_CURRENT_BINARY_DIR}/CMakeFiles/try_run
+        ${CMAKE_CURRENT_BINARY_DIR}/CMakeFiles/check_fortran_source_runs.${ext}
+        RUN_OUTPUT_VARIABLE run_output
+    )
+    # message("compile_result: ${compile_result}")
+    if(compile_result)
+        # message("run_result: ${run_result}")
+        if(DEFINED check_FAIL_REGEX)
+            set(tmpVar FALSE)
+            foreach(regexp in check_FAIL_REGEXP)
+                string(REGEXP MATCH ${regexp} match run_output)
+                if(NOT (${match} STREQUAL ""))
+                    set(tmpVar TRUE)
+                    break()
+                endif()
+            endforeach()
+            set(${resultVar} ${tmpVar} PARENT_SCOPE)
+        else()
+            if(${run_result} EQUAL 0)
+                set(${resultVar} TRUE PARENT_SCOPE)
+            else()
+                set(${resultVar} FALSE PARENT_SCOPE)
+            endif()
+        endif()
+    else()
+        set(${resultVar} FALSE PARENT_SCOPE)
+    endif()
+endfunction()
+
+if(NOT (DEFINED _R16P_SUPPORTED))
+    check_fortran_source_runs("program r16p_support; integer, parameter :: r16p = selected_real_kind(33, 4931) - 16; stop r16p; end program r16p_support" _r16p_supported SRC_EXT f90)
+    message(STATUS "Checking wether ${CMAKE_Fortran_COMPILER} supports 16 byte reals -- ${_r16p_supported}")
+    set(_R16P_SUPPORTED ${_r16p_supported} CACHE BOOL "Fortran compiler supports 16 byte precision reals")
+endif()
+
+target_compile_definitions(${LIB}
+    PRIVATE
+       $<$<BOOL:${_R16P_SUPPORTED}>:_R16P_SUPPORTED>
+        ${_ascii_supported}
+        ${_ucs4_supported}
+)
 set_target_properties(${LIB} PROPERTIES
     VERSION
         ${PROJECT_VERSION}