diff --git a/utils.cmake b/utils.cmake
index 3758c8c..0b4faf9 100644
--- a/utils.cmake
+++ b/utils.cmake
@@ -120,8 +120,10 @@ function(setup_project)
             set(CMAKE_C_EXTENSIONS OFF PARENT_SCOPE)
             set(CMAKE_C_VISIBILITY_PRESET "hidden" PARENT_SCOPE)
             if(MSVC)
-                string(REGEX REPLACE "[-|/]w " " " CMAKE_C_FLAGS ${CMAKE_C_FLAGS})
-                string(REGEX REPLACE "[-|/]W[0|1|2|3|4|all|X] " " " CMAKE_C_FLAGS ${CMAKE_C_FLAGS})
+                if(NOT ("x${CMAKE_C_FLAGS}" STREQUAL "x"))
+                    string(REGEX REPLACE "[-|/]w " " " CMAKE_C_FLAGS ${CMAKE_C_FLAGS})
+                    string(REGEX REPLACE "[-|/]W[0|1|2|3|4|all|X] " " " CMAKE_C_FLAGS ${CMAKE_C_FLAGS})
+                endif()
                 if(PROJ_ARGS_NO_WARNING)
                     string(APPEND CMAKE_C_FLAGS " /w ")
                 elseif(PROJ_ARGS_MAX_WARNING)
@@ -134,13 +136,17 @@ function(setup_project)
                 endif()
                 set(CMAKE_C_FLAGS ${CMAKE_C_FLAGS} PARENT_SCOPE)
                 if(MSVC_VERSION GREATER_EQUAL 1920) # Visual Studio 2019 version 16.0
-                    string(REGEX REPLACE "[-|/]Ob[0|1|2|3] " " " CMAKE_C_FLAGS_RELEASE ${CMAKE_C_FLAGS_RELEASE})
+                    if(NOT ("x${CMAKE_C_FLAGS_RELEASE}" STREQUAL "x"))
+                        string(REGEX REPLACE "[-|/]Ob[0|1|2|3] " " " CMAKE_C_FLAGS_RELEASE ${CMAKE_C_FLAGS_RELEASE})
+                    endif()
                     string(APPEND CMAKE_C_FLAGS_RELEASE " /Ob3 ")
                     set(CMAKE_C_FLAGS_RELEASE ${CMAKE_C_FLAGS_RELEASE} PARENT_SCOPE)
                 endif()
             else()
-                string(REPLACE "-w " " " CMAKE_C_FLAGS ${CMAKE_C_FLAGS})
-                string(REGEX REPLACE "-W[all|extra|error|pedantic] " " " CMAKE_C_FLAGS ${CMAKE_C_FLAGS})
+                if(NOT ("x${CMAKE_C_FLAGS}" STREQUAL "x"))
+                    string(REPLACE "-w " " " CMAKE_C_FLAGS ${CMAKE_C_FLAGS})
+                    string(REGEX REPLACE "-W[all|extra|error|pedantic] " " " CMAKE_C_FLAGS ${CMAKE_C_FLAGS})
+                endif()
                 if(PROJ_ARGS_NO_WARNING)
                     string(APPEND CMAKE_C_FLAGS " -w ")
                 elseif(PROJ_ARGS_MAX_WARNING)
@@ -162,10 +168,12 @@ function(setup_project)
             set(CMAKE_CXX_EXTENSIONS OFF PARENT_SCOPE)
             set(CMAKE_CXX_VISIBILITY_PRESET "hidden" PARENT_SCOPE)
             if(MSVC)
-                string(REGEX REPLACE "[-|/]GR-? " " " CMAKE_CXX_FLAGS ${CMAKE_CXX_FLAGS})
-                string(REGEX REPLACE "[-|/]EH(a-?|r-?|s-?|c-?)+ " " " CMAKE_CXX_FLAGS ${CMAKE_CXX_FLAGS})
-                string(REGEX REPLACE "[-|/]w " " " CMAKE_CXX_FLAGS ${CMAKE_CXX_FLAGS})
-                string(REGEX REPLACE "[-|/]W[0|1|2|3|4|all|X] " " " CMAKE_CXX_FLAGS ${CMAKE_CXX_FLAGS})
+                if(NOT ("x${CMAKE_CXX_FLAGS}" STREQUAL "x"))
+                    string(REGEX REPLACE "[-|/]GR-? " " " CMAKE_CXX_FLAGS ${CMAKE_CXX_FLAGS})
+                    string(REGEX REPLACE "[-|/]EH(a-?|r-?|s-?|c-?)+ " " " CMAKE_CXX_FLAGS ${CMAKE_CXX_FLAGS})
+                    string(REGEX REPLACE "[-|/]w " " " CMAKE_CXX_FLAGS ${CMAKE_CXX_FLAGS})
+                    string(REGEX REPLACE "[-|/]W[0|1|2|3|4|all|X] " " " CMAKE_CXX_FLAGS ${CMAKE_CXX_FLAGS})
+                endif()
                 if(PROJ_ARGS_NO_WARNING)
                     string(APPEND CMAKE_CXX_FLAGS " /w ")
                 elseif(PROJ_ARGS_MAX_WARNING)
@@ -188,16 +196,17 @@ function(setup_project)
                 endif()
                 set(CMAKE_CXX_FLAGS ${CMAKE_CXX_FLAGS} PARENT_SCOPE)
                 if(MSVC_VERSION GREATER_EQUAL 1920) # Visual Studio 2019 version 16.0
-                    string(REGEX REPLACE "[-|/]Ob[0|1|2|3] " " " CMAKE_CXX_FLAGS_RELEASE ${CMAKE_CXX_FLAGS_RELEASE})
+                    if(NOT ("x${CMAKE_CXX_FLAGS_RELEASE}" STREQUAL "x"))
+                        string(REGEX REPLACE "[-|/]Ob[0|1|2|3] " " " CMAKE_CXX_FLAGS_RELEASE ${CMAKE_CXX_FLAGS_RELEASE})
+                    endif()
                     string(APPEND CMAKE_CXX_FLAGS_RELEASE " /Ob3 ")
                     set(CMAKE_CXX_FLAGS_RELEASE ${CMAKE_CXX_FLAGS_RELEASE} PARENT_SCOPE)
                 endif()
             else()
-                if("x${CMAKE_CXX_FLAGS}" STREQUAL "x")
-                    message(FATAL_ERROR "CMAKE_CXX_FLAGS is empty!!!!!!!!!!")
+                if(NOT ("x${CMAKE_CXX_FLAGS}" STREQUAL "x"))
+                    string(REPLACE "-w " " " CMAKE_CXX_FLAGS ${CMAKE_CXX_FLAGS})
+                    string(REGEX REPLACE "-W[all|extra|error|pedantic] " " " CMAKE_CXX_FLAGS ${CMAKE_CXX_FLAGS})
                 endif()
-                string(REPLACE "-w " " " CMAKE_CXX_FLAGS ${CMAKE_CXX_FLAGS})
-                string(REGEX REPLACE "-W[all|extra|error|pedantic] " " " CMAKE_CXX_FLAGS ${CMAKE_CXX_FLAGS})
                 if(PROJ_ARGS_NO_WARNING)
                     string(APPEND CMAKE_CXX_FLAGS " -w ")
                 elseif(PROJ_ARGS_MAX_WARNING)