libstore: downsize hook pipes

don't keep fds open we're not using. currently this does not cause any
problems, but it does increase the size of our fd table needlessly and
in the future, when we have proper async processing, having builderOut
open in the daemon once the hook has been fully started is problematic

Change-Id: I6e7fb773b280b042873103638d3e04272ca1e4fc

1 files changed, 4 insertions, 4 deletions

diff --git a/src/libstore/build/hook-instance.hh b/src/libstore/build/hook-instance.hh
index 481158296..b8632d299 100644
--- a/src/libstore/build/hook-instance.hh
+++ b/src/libstore/build/hook-instance.hh
@@ -10,19 +10,19 @@ namespace nix {
 struct HookInstance
 {
     /**
-     * Pipes for talking to the build hook.
+     * Pipe for talking to the build hook.
      */
-    Pipe toHook;
+    AutoCloseFD toHook;
 
     /**
      * Pipe for the hook's standard output/error.
      */
-    Pipe fromHook;
+    AutoCloseFD fromHook;
 
     /**
      * Pipe for the builder's standard output/error.
      */
-    Pipe builderOut;
+    AutoCloseFD builderOut;
 
     /**
      * The process ID of the hook.