From eff403b5abc45851d683989f35dd60d40fcda267 Mon Sep 17 00:00:00 2001
From: John Ericson <John.Ericson@Obsidian.Systems>
Date: Sun, 14 Dec 2025 00:49:20 -0500
Subject: [PATCH] Inline `DerivationBuildingGoal::builder`

---
 .../build/derivation-building-goal.cc         | 23 ++++---------------
 .../store/build/derivation-building-goal.hh   |  6 -----
 2 files changed, 4 insertions(+), 25 deletions(-)

diff --git a/src/libstore/build/derivation-building-goal.cc b/src/libstore/build/derivation-building-goal.cc
index cb7d4d807..cc467daf0 100644
--- a/src/libstore/build/derivation-building-goal.cc
+++ b/src/libstore/build/derivation-building-goal.cc
@@ -44,10 +44,6 @@ DerivationBuildingGoal::~DerivationBuildingGoal()
 {
     /* Careful: we should never ever throw an exception from a
        destructor. */
-#ifndef _WIN32 // TODO enable `DerivationBuilder` on Windows
-    if (builder)
-        builder.reset();
-#endif
     try {
         closeLogFile();
     } catch (...) {
@@ -409,9 +405,6 @@ Goal::Co DerivationBuildingGoal::tryToBuild()
                             Magenta(
                                 "/usr/sbin/softwareupdate --install-rosetta && launchctl stop org.nixos.nix-daemon"));
 
-#ifndef _WIN32 // TODO enable `DerivationBuilder` on Windows
-                    builder.reset();
-#endif
                     outputLocks.unlock();
                     worker.permanentFailure = true;
                     co_return doneFailure({BuildResult::Failure::InputRejected, std::move(msg)});
@@ -584,6 +577,7 @@ Goal::Co DerivationBuildingGoal::tryToBuild()
 #else
     assert(!hook);
 
+    std::unique_ptr<DerivationBuilder> builder;
     Descriptor builderOut;
 
     // Will continue here while waiting for a build user below
@@ -711,9 +705,9 @@ Goal::Co DerivationBuildingGoal::tryToBuild()
     while (true) {
         auto event = co_await WaitForChildEvent{};
         if (auto * output = std::get_if<ChildOutput>(&event)) {
-            if (isReadDesc(output->fd)) {
+            if (output->fd == builder->builderOut.get()) {
                 if (processChildOutput(output->data)) {
-                    if (builder && builder->killChild())
+                    if (builder->killChild())
                         worker.childTerminated(this);
                     co_return doneFailureLogTooLong();
                 }
@@ -723,7 +717,7 @@ Goal::Co DerivationBuildingGoal::tryToBuild()
                 flushLine();
             break;
         } else if (auto * timeout = std::get_if<TimedOut>(&event)) {
-            if (builder && builder->killChild())
+            if (builder->killChild())
                 worker.childTerminated(this);
             co_return doneFailure(std::move(*timeout));
         }
@@ -1053,15 +1047,6 @@ void DerivationBuildingGoal::closeLogFile()
     fdLogFile.close();
 }
 
-bool DerivationBuildingGoal::isReadDesc(Descriptor fd)
-{
-#ifdef _WIN32 // TODO enable build hook on Windows
-    return false;
-#else
-    return builder && fd == builder->builderOut.get();
-#endif
-}
-
 bool DerivationBuildingGoal::processChildOutput(std::string_view data)
 {
     logSize += data.size();
diff --git a/src/libstore/include/nix/store/build/derivation-building-goal.hh b/src/libstore/include/nix/store/build/derivation-building-goal.hh
index 5fa727d2c..3072aed0a 100644
--- a/src/libstore/include/nix/store/build/derivation-building-goal.hh
+++ b/src/libstore/include/nix/store/build/derivation-building-goal.hh
@@ -81,10 +81,6 @@ private:
     std::string currentLogLine;
     size_t currentLogLinePos = 0; // to handle carriage return
 
-#ifndef _WIN32 // TODO enable build hook on Windows
-    std::unique_ptr<DerivationBuilder> builder;
-#endif
-
     BuildMode buildMode;
 
     std::unique_ptr<MaintainCount<uint64_t>> mcRunningBuilds;
@@ -119,8 +115,6 @@ private:
      */
     void closeLogFile();
 
-    bool isReadDesc(Descriptor fd);
-
     /**
      * Process log output from a child process.
      *