From 2f92f231dec9a00476aaadc60ba9874887d8cdbd 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 5b2490472..b70546cbc 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>
@@ -1327,13 +1328,15 @@ 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;