Similar to WordPress, WP-Members has pluggable functions. This allows you to replace a function in the plugin without modifying the plugin’s core code, a bad practice that makes upgrading difficult. Using pluggable functions for customizations makes upgrading easier, since your custom functions are maintained outside of the plugin’s files and are not overwritten when you upgrade.
It should be noted that even using pluggable functions, you can break the plugin. You should pay careful attention to the original function(s) and what they are doing. Also, when you upgrade, you should review the upgrade’s changes/updates and checked your custom functions to see if there are any compatibility issues to be addressed. If there have been changes to a function you are maintaining a custom version of, you should carefully review to see if you need to update your customization.
Here is list of pluggable functions found in the plugin:
file: wp-members-core.php
wpmem
wpmem_securify
wpmem_do_sc_pages
wpmem_block
wpmem_test_shortcode
wpmem_login
wpmem_logout
wpmem_login_status
wpmem_inc_sidebar
widget_wpmemwidget_init
wpmem_change_password
wpmem_reset_password
wpmem_no_reset
wpmem_create_formfield
wpmem_selected
wpmem_chk_qstr
wpmem_generatePassword
wpmem_enqueue_style
file: wp-members-dialogs.php
wpmem_inc_login
wpmem_inc_changepassword
wpmem_inc_resetpassword
wpmem_inc_loginfailed
wpmem_inc_memberlinks
wpmem_inc_regmessage
wpmem_inc_registration
wpmem_login_form
wpmem_inc_registration_NEW (to be deprecated)
wpmem_login_form_NEW (to be deprecated)
wpmem_inc_recaptcha
wpmem_page_pwd_reset
wpmem_page_user_edit
file: wp-members-register.php
wpmem_registration
wpmem_get_captcha_err
file: wp-members-sidebar.php
wpmem_inc_status
wpmem_do_sidebar