#   sudo gem install memcached --no-rdoc --no-ri
Building native extensions.  This could take a while...
ERROR:  Error installing memcached:
	ERROR: Failed to build gem native extension.

/usr/local/bin/ruby18 extconf.rb install memcached --no-rdoc --no-ri
checking for memcached_server_add() in -lmemcached... yes
checking for #include <libmemcached/memcached.h>
... no
*** extconf.rb failed ***
Could not create Makefile due to some reason, probably lack of
necessary libraries and/or headers.  Check the mkmf.log file for more
details.  You may need configuration options.

Provided configuration options:
	--with-opt-dir
	--without-opt-dir
	--with-opt-include
	--without-opt-include=${opt-dir}/include
	--with-opt-lib
	--without-opt-lib=${opt-dir}/lib
	--with-make-prog
	--without-make-prog
	--srcdir=.
	--curdir
	--ruby=/usr/local/bin/ruby18
	--with-rlibmemcached-dir
	--without-rlibmemcached-dir
	--with-rlibmemcached-include
	--without-rlibmemcached-include=${rlibmemcached-dir}/include
	--with-rlibmemcached-lib
	--without-rlibmemcached-lib=${rlibmemcached-dir}/lib
	--with-memcachedlib
	--without-memcachedlib
extconf.rb:31: header file 'Object' not  found (RuntimeError)
	from extconf.rb:25:in `each'
	from extconf.rb:25


Gem files will remain installed in /usr/local/lib/ruby/gems/1.8/gems/memcached-0.9 for inspection.
Results logged to /usr/local/lib/ruby/gems/1.8/gems/memcached-0.9/ext/gem_make.out


# cat /usr/local/lib/ruby/gems/1.8/gems/memcached-0.9/ext/mkmf.log
find_library: checking for memcached_server_add() in -lmemcached... -------------------- yes

"cc -o conftest -I. -I/usr/local/lib/ruby/1.8/amd64-freebsd7 -I.   -fno-strict-aliasing -pipe    -fPIC -O3 conftest.c  -L'.' -L'/usr/local/lib' -Wl,-R'/usr/local/lib' -L.  -rdynamic     -lruby18-static -lmemcached  -lcrypt -lm  -rpath=/usr/lib:/usr/local/lib -pthread  -lc"
conftest.c: In function 't':
conftest.c:3: error: 'memcached_server_add' undeclared (first use in this function)
conftest.c:3: error: (Each undeclared identifier is reported only once
conftest.c:3: error: for each function it appears in.)
checked program was:
/* begin */
1: /*top*/
2: int main() { return 0; }
3: int t() { void ((*volatile p)()); p = (void ((*)()))memcached_server_add; return 0; }
/* end */

"cc -o conftest -I. -I/usr/local/lib/ruby/1.8/amd64-freebsd7 -I.   -fno-strict-aliasing -pipe    -fPIC -O3 conftest.c  -L'.' -L'/usr/local/lib' -Wl,-R'/usr/local/lib' -L.  -rdynamic     -lruby18-static -lmemcached  -lcrypt -lm  -rpath=/usr/lib:/usr/local/lib -pthread  -lc"
checked program was:
/* begin */
1: /*top*/
2: int main() { return 0; }
3: int t() { memcached_server_add(); return 0; }
/* end */

--------------------

find_header: checking for #include <libmemcached/memcached.h>
... -------------------- no

"cc -E -I. -I/usr/local/lib/ruby/1.8/amd64-freebsd7 -I.   -fno-strict-aliasing -pipe    -fPIC -O3  conftest.c -o conftest.i"
conftest.c:1:36: error: libmemcached/memcached.h: No such file or directory
checked program was:
/* begin */
1: #include <libmemcached/memcached.h>
/* end */

--------------------