From b8258a4475726b56a4caa6553568c67a343a091d Mon Sep 17 00:00:00 2001
From: Eelco Dolstra <eelco.dolstra@logicblox.com>
Date: Tue, 29 Dec 2015 15:28:20 +0100
Subject: [PATCH] Fix regression in passAsFile

Caused by 8063fc497ab78fa72962b93874fe25dcca2b55ed. If tmpDir !=
tmpDirInSandbox (typically when there are multiple concurrent builds
with the same name), the *Path attribute would not point to an
existing file. This caused Nixpkgs' writeTextFile to write an empty
file. In particular this showed up as hanging VM builds (because it
would run an empty run-nixos-vm script and then wait for it to finish
booting).
---
 src/libstore/build.cc | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/src/libstore/build.cc b/src/libstore/build.cc
index 0fd958846..e00a07d3b 100644
--- a/src/libstore/build.cc
+++ b/src/libstore/build.cc
@@ -1778,10 +1778,11 @@ void DerivationGoal::startBuilder()
         if (passAsFile.find(i.first) == passAsFile.end()) {
             env[i.first] = i.second;
         } else {
-            Path p = tmpDir + "/.attr-" + std::to_string(fileNr++);
+            string fn = ".attr-" + std::to_string(fileNr++);
+            Path p = tmpDir + "/" + fn;
             writeFile(p, i.second);
             filesToChown.insert(p);
-            env[i.first + "Path"] = p;
+            env[i.first + "Path"] = tmpDirInSandbox + "/" + fn;
         }
     }