From e241a63c23239adf54fe69baf02f3159222b71e4 Mon Sep 17 00:00:00 2001
From: Pieter Wuille <pieter.wuille@gmail.com>
Date: Mon, 5 Jun 2017 12:17:40 -0700
Subject: [PATCH] Clarify prevector::erase and avoid swap-to-clear

---
 src/prevector.h     | 6 ++++++
 src/script/script.h | 5 +++--
 2 files changed, 9 insertions(+), 2 deletions(-)

diff --git a/src/prevector.h b/src/prevector.h
index 177d81383e9..dc17e7ce4b5 100644
--- a/src/prevector.h
+++ b/src/prevector.h
@@ -387,6 +387,12 @@ public:
     }
 
     iterator erase(iterator first, iterator last) {
+        // Erase is not allowed to the change the object's capacity. That means
+        // that when starting with an indirectly allocated prevector with
+        // size and capacity > N, the result may be a still indirectly allocated
+        // prevector with size <= N and capacity > N. A shrink_to_fit() call is
+        // necessary to switch to the (more efficient) directly allocated
+        // representation (with capacity N and size <= N).
         iterator p = first;
         char* endp = (char*)&(*end());
         if (!std::is_trivially_destructible<T>::value) {
diff --git a/src/script/script.h b/src/script/script.h
index 95a5999a13b..5f88e710123 100644
--- a/src/script/script.h
+++ b/src/script/script.h
@@ -642,8 +642,9 @@ public:
 
     void clear()
     {
-        // The default std::vector::clear() does not release memory.
-        CScriptBase().swap(*this);
+        // The default prevector::clear() does not release memory
+        CScriptBase::clear();
+        shrink_to_fit();
     }
 };