From 4cc6b1d4f304cb4d09f3b8dc150c645168ec13ad Mon Sep 17 00:00:00 2001
From: Lukasz Nocun <lukasznocun1@gmail.com>
Date: Wed, 30 Jun 2021 18:00:13 +0200
Subject: [PATCH] Fix possible UB when accessing empty vector's data

---
 src/lstm/networkscratch.h | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/src/lstm/networkscratch.h b/src/lstm/networkscratch.h
index f367374707..1637727706 100644
--- a/src/lstm/networkscratch.h
+++ b/src/lstm/networkscratch.h
@@ -148,7 +148,8 @@ class NetworkScratch {
       vec_ = scratch_space_->vec_stack_.Borrow();
       vec_->reserve(reserve);
       vec_->resize(size);
-      data_ = &(*vec_)[0];
+      // use vector.at(0) to make sure we do not trigger UB on an empty vector
+      data_ = &vec_->at(0);
     }
 
     void Init(int size, NetworkScratch *scratch) {