fixed-output.patch

diff --git a/src/libstore/build/local-derivation-goal.cc b/src/libstore/build/local-derivation-goal.cc
index f4342011f..eedd7e3d2 100644
--- a/src/libstore/build/local-derivation-goal.cc
+++ b/src/libstore/build/local-derivation-goal.cc
@@ -2308,17 +2308,36 @@ void LocalDerivationGoal::registerOutputs()
                     refs.first);
             if (scratchPath != finalPath) {
                 // Also rewrite the output path
-                auto source = sinkToSource([&](Sink & nextSink) {
-                    StringSink sink;
-                    dumpPath(actualPath, sink);
-                    RewritingSink rsink2(oldHashPart, std::string(finalPath.hashPart()), nextSink);
-                    rsink2(*sink.s);
-                    rsink2.flush();
-                });
-                Path tmpPath = actualPath + ".tmp";
-                restorePath(tmpPath, *source);
-                deletePath(actualPath);
-                movePath(tmpPath, actualPath);
+                AutoDelete tmpDir(createTempDir(), true);
+                Path tmpFile = (Path) tmpDir + "/rewrite";
+                {
+                  AutoCloseFD fd = open(tmpFile.c_str(), O_WRONLY | O_CREAT | O_EXCL, 0600);
+                  if(!fd) throw SysError("creating temporary file '%s'", tmpFile);
+                  FdSink sink(fd.get());
+                  dumpPath(actualPath, sink);
+                  deletePath(actualPath);
+                }
+                
+                {
+                  auto newHashPart = std::string(finalPath.hashPart());
+                  AutoCloseFD fd = open(tmpFile.c_str(), O_RDWR);
+                  if(!fd) throw SysError("Opening temporary file '%s'", tmpFile);
+                  struct stat stat_buf;
+                  if(fstat(fd.get(), &stat_buf) == -1) throw SysError("fstat: '%s'", tmpFile);
+                  void *ptr = mmap(NULL, stat_buf.st_size, PROT_READ | PROT_WRITE, MAP_SHARED, fd.get(), 0);
+                  if(!ptr) throw SysError("mmap: '%s'", tmpFile);
+                  void *j;
+                  while((j = memmem(ptr, stat_buf.st_size, oldHashPart.c_str(), oldHashPart.size())))
+                    memcpy(j, newHashPart.c_str(), newHashPart.size());
+                  munmap(ptr, stat_buf.st_size);
+                }
+                
+                {
+                  AutoCloseFD fd = open(tmpFile.c_str(), O_RDONLY);
+                  if(!fd) throw SysError("Opening temporary file '%s'", tmpFile);
+                  FdSource source(fd.get());
+                  restorePath(actualPath, source);
+                }
             }
 
             HashResult narHashAndSize = hashPath(htSHA256, actualPath);