Core: ngx_conf_set_keyval_slot() now accepts NGX_CONF_UNSET_PTR. With this change, it is now possible to use ngx_conf_merge_ptr_value() to merge keyval arrays. This change actually follows much earlier changes in ngx_conf_merge_ptr_value() and ngx_conf_set_str_array_slot() in 1452:cd586e963db0 (0.6.10) and 1701:40d004d95d88 (0.6.22). To preserve compatibility with existing 3rd party modules, both NULL and NGX_CONF_UNSET_PTR are accepted for now.

--- a/src/core/ngx_conf_file.c
+++ b/src/core/ngx_conf_file.c
@@ -1137,7 +1137,7 @@ ngx_conf_set_keyval_slot(ngx_conf_t *cf,
 
     a = (ngx_array_t **) (p + cmd->offset);
 
-    if (*a == NULL) {
+    if (*a == NGX_CONF_UNSET_PTR || *a == NULL) {
         *a = ngx_array_create(cf->pool, 4, sizeof(ngx_keyval_t));
         if (*a == NULL) {
             return NGX_CONF_ERROR;