reduce # of WordPress plugin/theme name calculation

Rather than figuring out the plugin/theme name at runtime, which is slow even
with memoisation in hashmap, we can do it only at the point an action or
filter is added and store it in the wraprec.

agent/fw_wordpress.c

@@ -348,7 +348,9 @@ static char* nr_wordpress_plugin_from_function(zend_function* func TSRMLS_DC) {
 }
 
 NR_PHP_WRAPPER(nr_wordpress_wrap_hook) {
+#if ZEND_MODULE_API_NO < ZEND_7_4_X_API_NO
   zend_function* func = NULL;
+#endif
   char* plugin = NULL;
 
   NR_UNUSED_SPECIALFN;
@@ -364,8 +366,12 @@ NR_PHP_WRAPPER(nr_wordpress_wrap_hook) {
   if ((0 == NRINI(wordpress_hooks)) || (NULL == NRPRG(wordpress_tag))) {
     NR_PHP_WRAPPER_LEAVE;
   }
+#if ZEND_MODULE_API_NO < ZEND_7_4_X_API_NO
   func = nr_php_execute_function(NR_EXECUTE_ORIG_ARGS TSRMLS_CC);
   plugin = nr_wordpress_plugin_from_function(func TSRMLS_CC);
+#else
+  plugin = wraprec->wordpress_plugin_theme;
+#endif
 
   NR_PHP_WRAPPER_CALL;
 
@@ -629,10 +635,23 @@ NR_PHP_WRAPPER(nr_wordpress_add_filter) {
   }
 
   if (true == wrap_hook) {
+    nruserfn_t* callback_wraprec;
     zval* callback = nr_php_arg_get(2, NR_EXECUTE_ORIG_ARGS TSRMLS_CC);
     /* the callback here can be any PHP callable. nr_php_wrap_generic_callable
    * checks that a valid callable is passed */
-    nr_php_wrap_generic_callable(callback, nr_wordpress_wrap_hook);
+    callback_wraprec = nr_php_wrap_generic_callable(callback, nr_wordpress_wrap_hook);
+
+    // We can cheat here: wraprecs on callables are always transient, so if
+    // there's a wordpress_plugin_theme set we know it's from this transaction,
+    // and we don't have any issues around a possible multi-tenant setup.
+    if (callback_wraprec && NULL == callback_wraprec->wordpress_plugin_theme) {
+      // Unlike Drupal, we don't free the wordpress_plugin_theme, since we know
+      // it's transient anyway, and we only set the field if it was previously
+      // NULL.
+      zend_function* fn = nr_php_zval_to_function(callback);
+      callback_wraprec->wordpress_plugin_theme
+          = nr_wordpress_plugin_from_function(fn);
+    }
     nr_php_arg_release(&callback);
   }
 }

agent/php_user_instrument.h

@@ -95,6 +95,9 @@ typedef struct _nruserfn_t {
   nr_string_len_t drupal_module_len;
   char* drupal_hook;
   nr_string_len_t drupal_hook_len;
+#if ZEND_MODULE_API_NO >= ZEND_7_4_X_API_NO
+  char* wordpress_plugin_theme;
+#endif
 } nruserfn_t;
 
 extern nruserfn_t* nr_wrapped_user_functions; /* a singly linked list */