Libmemcached already built; run ‘rake clean’ first if you need to rebuild.
在安装memcached后，安装memcached gem时会出现如下问题，解决方法如下：
在ruby/gems/1.8/gems/目录下删除memcached的安装目录memcached-1.2.5，有网友说使用gem uninstall memcached删除，但是我试用没有成功 sudo apt-get install libmemcached-dev libsasl2-dev libmemcached-dbg sudo gem install memcached
sudo gem install memcachedBuilding native extensions. This could take a while…ERROR: Error installing memcached:ERROR: Failed to build gem native extension./opt/ruby-enterprise-1.8.7-2010.02/bin/ruby extconf.rbLibmemcached already built; run ‘rake clean’ first if you need to rebuild.creating Makefilemakegcc -I. -I/opt/ruby-enterprise-1.8.7-2010.02/lib/ruby/1.8/x86_64-linux -I/opt/ruby-enterprise-1.8.7-2010.02/lib/ruby/1.8/x86_64-linux -I. -fPIC -I/opt/ruby-enterprise-1.8.7-2010.02/lib/ruby/gems/1.8/gems/memcached-0.19.7/ext/include -L/opt/ruby-enterprise-1.8.7-2010.02/lib/ruby/gems/1.8/gems/memcached-0.19.7/ext/lib -g -O2 -g -O2 -c rlibmemcached_wrap.crlibmemcached_wrap.c: In function ‘_wrap_MemcachedSt_sasl_callbacks_set’:rlibmemcached_wrap.c:6678: error: ‘sasl_callback_t’ undeclared (first use in this function)rlibmemcached_wrap.c:6678: error: (Each undeclared identifier is reported only oncerlibmemcached_wrap.c:6678: error: for each function it appears in.)rlibmemcached_wrap.c:6678: error: ‘arg2’ undeclared (first use in this function)rlibmemcached_wrap.c:6678: error: expected expression before ‘)’ tokenrlibmemcached_wrap.c:6696: error: expected expression before ‘)’ tokenrlibmemcached_wrap.c:6697: error: ‘struct memcached_st’ has no member named ‘sasl_callbacks’rlibmemcached_wrap.c:6697: error: expected ‘)’ before ‘const’rlibmemcached_wrap.c:6697: error: expected ‘;’ before ‘arg2’rlibmemcached_wrap.c: In function ‘_wrap_MemcachedSt_sasl_callbacks_get’:rlibmemcached_wrap.c:6709: error: ‘sasl_callback_t’ undeclared (first use in this function)rlibmemcached_wrap.c:6709: error: ‘result’ undeclared (first use in this function)rlibmemcached_wrap.c:6720: error: expected expression before ‘)’ tokenrlibmemcached_wrap.c:6720: error: ‘struct memcached_st’ has no member named ‘sasl_callbacks’rlibmemcached_wrap.c: In function ‘_wrap_memcached_set_sasl_callbacks’:rlibmemcached_wrap.c:12030: error: ‘sasl_callback_t’ undeclared (first use in this function)rlibmemcached_wrap.c:12030: error: ‘arg2’ undeclared (first use in this function)rlibmemcached_wrap.c:12030: error: expected expression before ‘)’ tokenrlibmemcached_wrap.c:12048: error: expected expression before ‘)’ tokenrlibmemcached_wrap.c:12049: error: expected ‘)’ before ‘const’rlibmemcached_wrap.c:12049: error: expected ‘)’ before ‘arg2’rlibmemcached_wrap.c: In function ‘_wrap_memcached_get_sasl_callbacks’:rlibmemcached_wrap.c:12131: error: ‘sasl_callback_t’ undeclared (first use in this function)rlibmemcached_wrap.c:12131: error: ‘result’ undeclared (first use in this function)rlibmemcached_wrap.c:12142: error: expected expression before ‘)’ tokenrlibmemcached_wrap.c: In function ‘Init_rlibmemcached’:rlibmemcached_wrap.c:13344: error: ‘SASL_OK’ undeclared (first use in this function)make: *** [rlibmemcached_wrap.o] Error 1Gem files will remain installed in /opt/ruby-enterprise-1.8.7-2010.02/lib/ruby/gems/1.8/gems/memcached-0.19.7 for inspection.Results logged to /opt/ruby-enterprise-1.8.7-2010.02/lib/ruby/gems/1.8/gems/memcached-0.19.7/ext/gem_make.outsudo gem install memcachedBuilding native extensions. This could take a while…ERROR: Error installing memcached:ERROR: Failed to build gem native extension./opt/ruby-enterprise-1.8.7-2010.02/bin/ruby extconf.rbLibmemcached already built; run ‘rake clean’ first if you need to rebuild.creating Makefilemakegcc -I. -I/opt/ruby-enterprise-1.8.7-2010.02/lib/ruby/1.8/x86_64-linux -I/opt/ruby-enterprise-1.8.7-2010.02/lib/ruby/1.8/x86_64-linux -I. -fPIC -I/opt/ruby-enterprise-1.8.7-2010.02/lib/ruby/gems/1.8/gems/memcached-0.19.7/ext/include -L/opt/ruby-enterprise-1.8.7-2010.02/lib/ruby/gems/1.8/gems/memcached-0.19.7/ext/lib -g -O2 -g -O2 -c rlibmemcached_wrap.crlibmemcached_wrap.c: In function ‘_wrap_MemcachedSt_sasl_callbacks_set’:rlibmemcached_wrap.c:6678: error: ‘sasl_callback_t’ undeclared (first use in this function)rlibmemcached_wrap.c:6678: error: (Each undeclared identifier is reported only oncerlibmemcached_wrap.c:6678: error: for each function it appears in.)rlibmemcached_wrap.c:6678: error: ‘arg2’ undeclared (first use in this function)rlibmemcached_wrap.c:6678: error: expected expression before ‘)’ tokenrlibmemcached_wrap.c:6696: error: expected expression before ‘)’ tokenrlibmemcached_wrap.c:6697: error: ‘struct memcached_st’ has no member named ‘sasl_callbacks’rlibmemcached_wrap.c:6697: error: expected ‘)’ before ‘const’rlibmemcached_wrap.c:6697: error: expected ‘;’ before ‘arg2’rlibmemcached_wrap.c: In function ‘_wrap_MemcachedSt_sasl_callbacks_get’:rlibmemcached_wrap.c:6709: error: ‘sasl_callback_t’ undeclared (first use in this function)rlibmemcached_wrap.c:6709: error: ‘result’ undeclared (first use in this function)rlibmemcached_wrap.c:6720: error: expected expression before ‘)’ tokenrlibmemcached_wrap.c:6720: error: ‘struct memcached_st’ has no member named ‘sasl_callbacks’rlibmemcached_wrap.c: In function ‘_wrap_memcached_set_sasl_callbacks’:rlibmemcached_wrap.c:12030: error: ‘sasl_callback_t’ undeclared (first use in this function)rlibmemcached_wrap.c:12030: error: ‘arg2’ undeclared (first use in this function)rlibmemcached_wrap.c:12030: error: expected expression before ‘)’ tokenrlibmemcached_wrap.c:12048: error: expected expression before ‘)’ tokenrlibmemcached_wrap.c:12049: error: expected ‘)’ before ‘const’rlibmemcached_wrap.c:12049: error: expected ‘)’ before ‘arg2’rlibmemcached_wrap.c: In function ‘_wrap_memcached_get_sasl_callbacks’:rlibmemcached_wrap.c:12131: error: ‘sasl_callback_t’ undeclared (first use in this function)rlibmemcached_wrap.c:12131: error: ‘result’ undeclared (first use in this function)rlibmemcached_wrap.c:12142: error: expected expression before ‘)’ tokenrlibmemcached_wrap.c: In function ‘Init_rlibmemcached’:rlibmemcached_wrap.c:13344: error: ‘SASL_OK’ undeclared (first use in this function)make: *** [rlibmemcached_wrap.o] Error 1Gem files will remain installed in /opt/ruby-enterprise-1.8.7-2010.02/lib/ruby/gems/1.8/gems/memcached-0.19.7 for inspection.Results logged to /opt/ruby-enterprise-1.8.7-2010.02/lib/ruby/gems/1.8/gems/memcached-0.19.7/ext/gem_make.out
