From d2ddce0a37cd5d41e3f5df29f0d10e0b2eb8facf Mon Sep 17 00:00:00 2001
From: Niels Lohmann <mail@nlohmann.me>
Date: Tue, 9 Nov 2021 14:52:16 +0100
Subject: [PATCH] :bug: avoid using an invalidated iterator

---
 include/nlohmann/ordered_map.hpp | 11 ++++++++---
 single_include/nlohmann/json.hpp | 11 ++++++++---
 2 files changed, 16 insertions(+), 6 deletions(-)

diff --git a/include/nlohmann/ordered_map.hpp b/include/nlohmann/ordered_map.hpp
index 1c161efdd..fb242633c 100644
--- a/include/nlohmann/ordered_map.hpp
+++ b/include/nlohmann/ordered_map.hpp
@@ -112,11 +112,14 @@ template <class Key, class T, class IgnoredLess = std::less<Key>,
 
     iterator erase(iterator first, iterator last)
     {
-        auto elements_affected = std::distance(first, last);
+        const auto offset = std::distance(Container::begin(), first);
+        const auto elements_affected = std::distance(first, last);
 
         // This is the start situation. We need to delete elements_affected
         // elements (3 in this example: e, f, g), and need to return an
         // iterator past the last deleted element (h in this example).
+        // Note that offset is the distance from the start of the vector
+        // to first. We will need this later.
 
         // [ a, b, c, d, e, f, g, h, i, j ]
         //               ^        ^
@@ -149,8 +152,10 @@ template <class Key, class T, class IgnoredLess = std::less<Key>,
         //               ^        ^
         //             first    last
 
-        // first is now pointing past the last deleted element
-        return first;
+        // first is now pointing past the last deleted element, but we cannot
+        // use this iterator got invalidated by the resize call. Instead, we
+        // can return begin() + offset.
+        return Container::begin() + offset;
     }
 
     size_type count(const Key& key) const
diff --git a/single_include/nlohmann/json.hpp b/single_include/nlohmann/json.hpp
index 3743fb8e0..dffa48d19 100644
--- a/single_include/nlohmann/json.hpp
+++ b/single_include/nlohmann/json.hpp
@@ -17499,11 +17499,14 @@ template <class Key, class T, class IgnoredLess = std::less<Key>,
 
     iterator erase(iterator first, iterator last)
     {
-        auto elements_affected = std::distance(first, last);
+        const auto offset = std::distance(Container::begin(), first);
+        const auto elements_affected = std::distance(first, last);
 
         // This is the start situation. We need to delete elements_affected
         // elements (3 in this example: e, f, g), and need to return an
         // iterator past the last deleted element (h in this example).
+        // Note that offset is the distance from the start of the vector
+        // to first. We will need this later.
 
         // [ a, b, c, d, e, f, g, h, i, j ]
         //               ^        ^
@@ -17536,8 +17539,10 @@ template <class Key, class T, class IgnoredLess = std::less<Key>,
         //               ^        ^
         //             first    last
 
-        // first is now pointing past the last deleted element
-        return first;
+        // first is now pointing past the last deleted element, but we cannot
+        // use this iterator got invalidated by the resize call. Instead, we
+        // can return begin() + offset.
+        return Container::begin() + offset;
     }
 
     size_type count(const Key& key) const