From 2f5c913d4a21c60799290d6efe769d188c57b906 Mon Sep 17 00:00:00 2001
From: John Ericson <John.Ericson@Obsidian.Systems>
Date: Tue, 30 Nov 2021 21:48:43 +0000
Subject: [PATCH] Fix #5299

No matter what, we need to resize the buffer to not have any scratch
space after we do the `read`. In the end of file case, `got` will be 0
from it's initial value.

Before, we forgot to resize in the EOF case with the break. Yes, we know
we didn't recieve any data in that case, but we still have the scatch
space to undo.

Co-Authored-By: Will Fancher <Will.Fancher@Obsidian.Systems>
---
 src/libstore/local-store.cc | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/src/libstore/local-store.cc b/src/libstore/local-store.cc
index 64019314f..3a1688272 100644
--- a/src/libstore/local-store.cc
+++ b/src/libstore/local-store.cc
@@ -8,6 +8,7 @@
 #include "references.hh"
 #include "callback.hh"
 #include "topo-sort.hh"
+#include "finally.hh"
 
 #include <iostream>
 #include <algorithm>
@@ -1333,13 +1334,15 @@ StorePath LocalStore::addToStoreFromDump(Source & source0, const string & name,
         auto want = std::min(chunkSize, settings.narBufferSize - oldSize);
         dump.resize(oldSize + want);
         auto got = 0;
+        Finally cleanup([&]() {
+            dump.resize(oldSize + got);
+        });
         try {
             got = source.read(dump.data() + oldSize, want);
         } catch (EndOfFile &) {
             inMemory = true;
             break;
         }
-        dump.resize(oldSize + got);
     }
 
     std::unique_ptr<AutoDelete> delTempDir;