Adding checks for compiler flags.

CMakeLists.txt

@@ -40,6 +40,23 @@ if(FLEX_BISON_WARN_SUPPRESS_FLAGS)
                                 PROPERTIES COMPILE_FLAGS ${FLEX_BISON_WARN_SUPPRESS_FLAGS})
 endif()
 
+# Grammars generated by Bison 3.0.4 and below emit a null pointer dereference warning
+# when compiled with GCC 7
+include(CheckCXXCompilerFlag)
+check_cxx_compiler_flag(-Werror=null-dereference NULL_DEREFERENCE)
+if (${NULL_DEREFERENCE} AND ${BISON_VERSION} VERSION_LESS 3.0.5)
+    get_source_file_property(BISON_COMPILE_FLAGS ${BISON_SdcParser_OUTPUT_SOURCE} COMPILE_FLAGS)
+    set_source_files_properties(${BISON_SdcParser_OUTPUT_SOURCE}
+                                PROPERTIES COMPILE_FLAGS ${BISON_COMILE_FLAGS} -Wno-error=null-dereference)
+endif()
+
+check_cxx_compiler_flag(-Wswitch-default SWITCH_DEFAULT)
+if (${SWITCH_DEFAULT})
+    get_source_file_property(BISON_COMPILE_FLAGS ${BISON_SdcParser_OUTPUT_SOURCE} COMPILE_FLAGS)
+    set_source_files_properties(${BISON_SdcParser_OUTPUT_SOURCE}
+                                PROPERTIES COMPILE_FLAGS ${BISON_COMILE_FLAGS} -Wno-switch-default)
+endif()
+
 #Create the library
 add_library(libsdcparse STATIC
              ${LIB_HEADERS}