[1.x] CMake: check actually needed system headers are used

CMakeLists.txt

@@ -26,11 +26,28 @@ feature_info_on_off(DISABLE_CMAKE_CONFIG "won't generate CMake config file" "wil
 option(ENABLE_WIN32_IO "Build the Windows I/O helper class" OFF)
 feature_info_on_off(ENABLE_WIN32_IO "will build Windows I/O code" "will not build Windows I/O code")
 
+option(DEV_MODE "Developer mode with extra compilation checks" OFF)
+feature_info_on_off(DEV_MODE "added developer mode extra compilation checks" "default build mode")
+
 include(GNUInstallDirs)
 
 set(CMAKE_CXX_STANDARD 14)
 set(CMAKE_CXX_STANDARD_REQUIRED ON)
 
+include(CheckCXXCompilerFlag)
+include(CMakeParseArguments)
+function(add_cxx_flag_if_supported)
+  foreach(flagname ${ARGN})
+    string(REPLACE "-" "_" TEST_RESULT ${flagname})
+    check_cxx_compiler_flag(${flagname} HAVE_FLAG_${TEST_RESULT})
+    # message(STATUS "supported ${flagname}: ${HAVE_FLAG_${TEST_RESULT}}")
+
+    if (HAVE_FLAG_${TEST_RESULT})
+      add_compile_options(${flagname})
+    endif()
+  endforeach()
+endfunction()
+
 find_package(utf8cpp 3.2.0)
 if(NOT utf8cpp_FOUND)
   include(FetchContent REQUIRED)
@@ -45,6 +62,16 @@ if(NOT utf8cpp_FOUND)
     FetchContent_MakeAvailable(utf8cpp)
 endif()
 
+if(DEV_MODE)
+  message(STATUS "Using developer mode for ${CMAKE_CXX_COMPILER_ID}")
+  set(CMAKE_CXX_EXTENSIONS OFF)
+  add_definitions("-D_LIBCPP_REMOVE_TRANSITIVE_INCLUDES")
+  add_cxx_flag_if_supported(-Wno-error=unused-command-line-argument
+                            -Wall -Wextra -Wpedantic -Wfatal-errors -fstack-protector-strong
+                            -Wcast-align
+                            -W4)
+endif()
+
 set(libebml_SOURCES
   src/Debug.cpp
   src/EbmlBinary.cpp