From 2550c11373e83f4c6085049dc9efe53f8389b035 Mon Sep 17 00:00:00 2001
From: Eelco Dolstra <edolstra@gmail.com>
Date: Thu, 19 Dec 2019 15:08:16 +0100
Subject: [PATCH] tarfile.cc: Don't change the cwd

Nix is multithreaded so it's not safe to change the cwd.
---
 src/libutil/tarfile.cc | 27 ++++-----------------------
 1 file changed, 4 insertions(+), 23 deletions(-)

diff --git a/src/libutil/tarfile.cc b/src/libutil/tarfile.cc
index c85a8b0cb..ca19f402e 100644
--- a/src/libutil/tarfile.cc
+++ b/src/libutil/tarfile.cc
@@ -80,34 +80,12 @@ private:
     }
 };
 
-struct PushD {
-    char * oldDir;
-
-    PushD(const std::string &newDir)  {
-        oldDir = getcwd(0, 0);
-        if (!oldDir) throw SysError("getcwd");
-        int r = chdir(newDir.c_str());
-        if (r != 0) throw SysError("changing directory to tar output path");
-    }
-
-    ~PushD() {
-        int r = chdir(oldDir);
-        free(oldDir);
-        if (r != 0)
-            warn("failed to change directory back after tar extraction");
-        /* can't throw out of a destructor */
-    }
-};
-
 static void extract_archive(TarArchive & archive, const Path & destDir)
 {
-    // need to chdir back *after* archive closing
-    PushD newDir(destDir);
     int flags = ARCHIVE_EXTRACT_FFLAGS
         | ARCHIVE_EXTRACT_PERM
         | ARCHIVE_EXTRACT_SECURE_SYMLINKS
-        | ARCHIVE_EXTRACT_SECURE_NODOTDOT
-        | ARCHIVE_EXTRACT_SECURE_NOABSOLUTEPATHS;
+        | ARCHIVE_EXTRACT_SECURE_NODOTDOT;
 
     for (;;) {
         struct archive_entry * entry;
@@ -118,6 +96,9 @@ static void extract_archive(TarArchive & archive, const Path & destDir)
         else
             archive.check(r);
 
+        archive_entry_set_pathname(entry,
+            (destDir + "/" + archive_entry_pathname(entry)).c_str());
+
         archive.check(archive_read_extract(archive.archive, entry, flags));
     }