Hi there,
Despite libcouchbase being properly installed via Homebrew:
brew install libcouchbase --universal Warning: libcouchbase-2.7.3 already installed
I keep running into the same error:
sudo gem install couchbase
Building native extensions. This could take a while...
ERROR: Error installing couchbase:
ERROR: Failed to build gem native extension.
current directory: /Library/Ruby/Gems/2.0.0/gems/couchbase-1.3.15/ext/couchbase_ext
/System/Library/Frameworks/Ruby.framework/Versions/2.0/usr/bin/ruby -r ./siteconf20170401-31238-19lf42h.rb extconf.rb
checking for lcb_iops_wire_bsd_impl2(NULL, 0) in -lcouchbase... no
**********************************************************************
* You must install libcouchbase >= 2.4.5
* See http://www.couchbase.com/communities/c/ for more details
**********************************************************************
*** 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=/System/Library/Frameworks/Ruby.framework/Versions/2.0/usr/bin/ruby
--with-libcouchbase-dir
--without-libcouchbase-dir
--with-libcouchbase-include
--without-libcouchbase-include=${libcouchbase-dir}/include
--with-libcouchbase-lib
--without-libcouchbase-lib=${libcouchbase-dir}/
--with-couchbaselib
--without-couchbaselib
To see why this extension failed to compile, please check the mkmf.log which can be found here:
/Library/Ruby/Gems/2.0.0/extensions/universal-darwin-16/2.0.0/couchbase-1.3.15/mkmf.log
extconf failed, exit code 1
Gem files will remain installed in /Library/Ruby/Gems/2.0.0/gems/couchbase-1.3.15 for inspection.
Results logged to /Library/Ruby/Gems/2.0.0/extensions/universal-darwin-16/2.0.0/couchbase-1.3.15/gem_make.out
My mkmf.log is as follow:
"xcrun clang -o conftest -I/System/Library/Frameworks/Ruby.framework/Versions/2.0/usr/include/ruby-2.0.0/universal-darwin16 -I/System/Library/Frameworks/Ruby.framework/Versions/2.0/usr/include/ruby-2.0.0/ruby/backward -I/System/Library/Frameworks/Ruby.framework/Versions/2.0/usr/include/ruby-2.0.0 -I. -I/usr/local/opt/libcouchbase/include -I/usr/local/include -I/System/Library/Frameworks/Ruby.framework/Versions/2.0/usr/include -I/usr/include -D_XOPEN_SOURCE -D_DARWIN_C_SOURCE -D_DARWIN_UNLIMITED_SELECT -D_REENTRANT -g -Os -pipe -DHAVE_GCC_SYNC_BUILTINS -std=c99 -Wall -Wextra -O2 conftest.c -L. -L/System/Library/Frameworks/Ruby.framework/Versions/2.0/usr/lib -L/usr/local/opt/libcouchbase/lib -L/usr/local/lib -L/System/Library/Frameworks/Ruby.framework/Versions/2.0/usr/lib -L/usr/lib -L. -L/usr/local/lib -arch i386 -arch x86_64 -lruby.2.0.0 -lcouchbase -lpthread -ldl -lobjc "
conftest.c:8:27: warning: unused parameter 'argv' [-Wunused-parameter]
int main(int argc, char **argv)
^
1 warning generated.
ld: warning: ignoring file /usr/local/opt/libcouchbase/lib/libcouchbase.dylib, file was built for x86_64 which is not the architecture being linked (i386): /usr/local/opt/libcouchbase/lib/libcouchbase.dylib
Undefined symbols for architecture i386:
"_lcb_iops_wire_bsd_impl2", referenced from:
_t in conftest-c8edbb.o
ld: symbol(s) not found for architecture i386
clang: error: linker command failed with exit code 1 (use -v to see invocation)
checked program was:
/* begin */
1: #include "ruby.h"
2:
3: #include <libcouchbase/couchbase.h>
4:
5: /*top*/
6: extern int t(void);
7: int t(void) { lcb_iops_wire_bsd_impl2(NULL, 0); return 0; }
8: int main(int argc, char **argv)
9: {
10: if (argc > 1000000) {
11: printf("%p", &t);
12: }
13:
14: return 0;
15: }
/* end */
Thank you for any help you can provide 
Jean