From cc08a661e64b0512105efccc97e389305b7d5c0c Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Oliver=20St=C3=B6neberg?=
 <firewave@users.noreply.github.com>
Date: Fri, 3 Jun 2022 19:21:17 +0200
Subject: [PATCH] astutils.h: reserve `std::vector` space in `visitAstNodes()`
 to avoid excess allocations (#4158)

---
 lib/astutils.h | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/lib/astutils.h b/lib/astutils.h
index 6bdde92b1..0dafe305d 100644
--- a/lib/astutils.h
+++ b/lib/astutils.h
@@ -53,7 +53,11 @@ void visitAstNodes(T *ast, const TFunc &visitor)
     if (!ast)
         return;
 
-    std::stack<T *, std::vector<T *>> tokens;
+    std::vector<T *> tokensContainer;
+    // the size of 8 was determined in tests to be sufficient to avoid excess allocations. also add 1 as a buffer.
+    // we might need to increase that value in the future.
+    tokensContainer.reserve(8 + 1);
+    std::stack<T *, std::vector<T *>> tokens(std::move(tokensContainer));
     T *tok = ast;
     do {
         ChildrenToVisit c = visitor(tok);