Test struct existance against sizeof() operator Instead of declaring an "unused-variable" or "unused-but-set-variable" structure. This avoid unexpected broken configurations when using something like: $ ./configure CFLAGS="-Wall -Wextra -Werror" It causes AC_COMPILE_IFELSE to fail and thus leading to a mismatch configuration (because the CFLAGS are passed to the macro).

/etc/init.d/dropbear
/etc/dropbear/run
/etc/dropbear/log/run