evaluate maximum captures size on configuration phase

src/http/ngx_http_core_module.c

diff --git a/src/http/ngx_http_core_module.c b/src/http/ngx_http_core_module.c
index 7ae49a6..e6b1162 100644
--- a/src/http/ngx_http_core_module.c
+++ b/src/http/ngx_http_core_module.c
@@ -2759,6 +2759,10 @@
     cmcf->variables_hash_bucket_size =
                ngx_align(cmcf->variables_hash_bucket_size, ngx_cacheline_size);
 
+    if (cmcf->ncaptures) {
+        cmcf->ncaptures = (cmcf->ncaptures + 1) * 3;
+    }
+
     return NGX_CONF_OK;
 }
 

src/http/ngx_http_variables.c

diff --git a/src/http/ngx_http_variables.c b/src/http/ngx_http_variables.c
index 0289a64..a2852b0 100644
--- a/src/http/ngx_http_variables.c
+++ b/src/http/ngx_http_variables.c
@@ -1759,7 +1759,7 @@
     cmcf = ngx_http_get_module_main_conf(r, ngx_http_core_module);
 
     if (re->ncaptures) {
-        len = (cmcf->ncaptures + 1) * 3;
+        len = cmcf->ncaptures;
 
         if (r->captures == NULL) {
             r->captures = ngx_palloc(r->pool, len * sizeof(int));