$ gdb --args php -n -d zend_extension=xdebug.so -d extension=couchbase.so
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Reading symbols from php...Reading symbols from /usr/lib/debug//usr/bin/php5...done.
done.
(gdb) run
Starting program: /usr/bin/php -n -d zend_extension=xdebug.so -d extension=couchbase.so
[Thread debugging using libthread_db enabled]
Using host libthread_db library "/lib/x86_64-linux-gnu/libthread_db.so.1".

Program received signal SIGSEGV, Segmentation fault.
0x00007ffff575a4ce in xdebug_execute_internal (current_execute_data=0x7ffff7fa9640, fci=0x0, return_value_used=0)
at /build/buildd/xdebug-2.2.3/xdebug-2.2.3/xdebug.c:1589
1589 /build/buildd/xdebug-2.2.3/xdebug-2.2.3/xdebug.c: No such file or directory.
(gdb) bt
#0 0x00007ffff575a4ce in xdebug_execute_internal (current_execute_data=0x7ffff7fa9640, fci=0x0, return_value_used=0)
at /build/buildd/xdebug-2.2.3/xdebug-2.2.3/xdebug.c:1589
#1 0x000000000079da25 in zend_do_fcall_common_helper_SPEC (execute_data=<optimized out>) at /build/buildd/php5-5.5.9+dfsg/Zend/zend_vm_execute.h:552
0000002 0x0000000000717758 in execute_ex (execute_data=0x7ffff7fa9640) at /build/buildd/php5-5.5.9+dfsg/Zend/zend_vm_execute.h:363
0000003 0x00000000006dd8c9 in dtrace_execute_ex (execute_data=<optimized out>) at /build/buildd/php5-5.5.9+dfsg/Zend/zend_dtrace.c:73
0000004 0x00007ffff5759a7c in xdebug_execute_ex (execute_data=0x7ffff7fa9640) at /build/buildd/xdebug-2.2.3/xdebug-2.2.3/xdebug.c:1437
0000005 0x00000000006e175a in zend_eval_stringl (
str=0x7ffff5540b40 "/*\n Various constants used for flags, data-type encoding and decoding, etc...\n throughout this SDK.\n \n @author Brett Lawson brett19@gmail.com\n /\n\n/* @internal / define('COUCHBASE_VAL_MASK"..., str_len=<optimized out>, retval_ptr=retval_ptr@entry=0x0,
string_name=string_name@entry=0x7ffff5540abb "CouchbaseNative") at /build/buildd/php5-5.5.9+dfsg/Zend/zend_execute_API.c:1187
0000006 0x00000000006e1836 in zend_eval_string (str=<optimized out>, retval_ptr=retval_ptr@entry=0x0, string_name=string_name@entry=0x7ffff5540abb "CouchbaseNative")
at /build/buildd/php5-5.5.9+dfsg/Zend/zend_execute_API.c:1226
0000007 0x00007ffff553c97c in zm_activate_couchbase (type=<optimized out>, module_number=<optimized out>) at /tmp/pear/temp/couchbase/couchbase.c:63
0000008 0x00000000006f4dc0 in zend_activate_modules () at /build/buildd/php5-5.5.9+dfsg/Zend/zend_API.c:2398
0000009 0x000000000068d8ea in php_request_startup () at /build/buildd/php5-5.5.9+dfsg/main/main.c:1596
0000010 0x000000000079f1b1 in do_cli (argc=6, argv=0xebea10) at /build/buildd/php5-5.5.9+dfsg/sapi/cli/php_cli.c:965
0000011 0x0000000000461de0 in main (argc=6, argv=0xebea10) at /build/buildd/php5-5.5.9+dfsg/sapi/cli/php_cli.c:1378
(gdb)