Wshadow does not work with old gccs

CMakeLists.txt

@@ -21,7 +21,7 @@ endif()
 if(CMAKE_COMPILER_IS_GNUCC OR "${CMAKE_C_COMPILER_ID}" STREQUAL "Clang")
     add_definitions(-std=c99 -pipe -Wall -Wextra -Werror -Wformat -Wno-unused-parameter
                     -Wno-unused-function -Wno-unused-label -Wpointer-arith -Wreturn-type -Wsign-compare -Wmultichar
-                    -Wcast-qual -Wmissing-prototypes -Wstrict-prototypes -Wshadow # -Wconversion
+                    -Wcast-qual -Wmissing-prototypes -Wstrict-prototypes # -Wshadow -Wconversion
                     -Winit-self -Wuninitialized -Wformat-security -Wformat-nonliteral)
     # binary size reduction settings
 	add_definitions(-ffunction-sections -fdata-sections -fno-stack-protector -fno-unwind-tables