AC_DEFINE([_GNU_SOURCE],[1],[Use GNU C library extensions (e.g. stdndup).])
# set default gcc warnings
-GCC_WARNINGS="-Wall -Wstrict-prototypes -Wformat-security"
+GCC_WARNINGS="-Wall -Wstrict-prototypes -Wformat-security -Wshadow"
if test "${gcc_wextra}" = yes; then
GCC_WARNINGS="${GCC_WARNINGS} -Wextra -Wno-unused-parameter"
GCC_WARNINGS="${GCC_WARNINGS} -Wbad-function-cast"