From 49da508f46a1a90b04faed88a7d865976ae7c6fb Mon Sep 17 00:00:00 2001
From: John Ericson <John.Ericson@Obsidian.Systems>
Date: Thu, 28 Aug 2025 12:40:55 -0400
Subject: [PATCH] Write a destructor for `DerivationBuilderImpl`

This allows `DerivationBuildingGoal` to know less.
---
 .../build/derivation-building-goal.cc         | 14 ++------
 .../nix/store/build/derivation-builder.hh     | 14 --------
 src/libstore/unix/build/derivation-builder.cc | 36 ++++++++++++++++---
 3 files changed, 33 insertions(+), 31 deletions(-)

diff --git a/src/libstore/build/derivation-building-goal.cc b/src/libstore/build/derivation-building-goal.cc
index 24244ebd4..61f726bf9 100644
--- a/src/libstore/build/derivation-building-goal.cc
+++ b/src/libstore/build/derivation-building-goal.cc
@@ -59,18 +59,8 @@ DerivationBuildingGoal::~DerivationBuildingGoal()
         ignoreExceptionInDestructor();
     }
 #ifndef _WIN32 // TODO enable `DerivationBuilder` on Windows
-    if (builder) {
-        try {
-            builder->stopDaemon();
-        } catch (...) {
-            ignoreExceptionInDestructor();
-        }
-        try {
-            builder->cleanupBuild(false);
-        } catch (...) {
-            ignoreExceptionInDestructor();
-        }
-    }
+    if (builder)
+        builder.reset();
 #endif
     try {
         closeLogFile();
diff --git a/src/libstore/include/nix/store/build/derivation-builder.hh b/src/libstore/include/nix/store/build/derivation-builder.hh
index 512d001e0..65d044a79 100644
--- a/src/libstore/include/nix/store/build/derivation-builder.hh
+++ b/src/libstore/include/nix/store/build/derivation-builder.hh
@@ -192,20 +192,6 @@ struct DerivationBuilder : RestrictionContext
      */
     virtual SingleDrvOutputs unprepareBuild() = 0;
 
-    /**
-     * Stop the in-process nix daemon thread.
-     * @see startDaemon
-     */
-    virtual void stopDaemon() = 0;
-
-    /**
-     * Delete the temporary directory, if we have one.
-     *
-     * @param force We know the build suceeded, so don't attempt to
-     * preseve anything for debugging.
-     */
-    virtual void cleanupBuild(bool force) = 0;
-
     /**
      * Kill any processes running under the build user UID or in the
      * cgroup of the build.
diff --git a/src/libstore/unix/build/derivation-builder.cc b/src/libstore/unix/build/derivation-builder.cc
index 241d98ace..4678dae42 100644
--- a/src/libstore/unix/build/derivation-builder.cc
+++ b/src/libstore/unix/build/derivation-builder.cc
@@ -85,6 +85,22 @@ public:
     {
     }
 
+    ~DerivationBuilderImpl()
+    {
+        /* Careful: we should never ever throw an exception from a
+           destructor. */
+        try {
+            stopDaemon();
+        } catch (...) {
+            ignoreExceptionInDestructor();
+        }
+        try {
+            cleanupBuild(false);
+        } catch (...) {
+            ignoreExceptionInDestructor();
+        }
+    }
+
 protected:
 
     /**
@@ -285,9 +301,11 @@ private:
      */
     void startDaemon();
 
-public:
-
-    void stopDaemon() override;
+    /**
+     * Stop the in-process nix daemon thread.
+     * @see startDaemon
+     */
+    void stopDaemon();
 
 protected:
 
@@ -342,9 +360,17 @@ private:
      */
     SingleDrvOutputs registerOutputs();
 
-public:
+protected:
 
-    void cleanupBuild(bool force) override;
+    /**
+     * Delete the temporary directory, if we have one.
+     *
+     * @param force We know the build suceeded, so don't attempt to
+     * preseve anything for debugging.
+     */
+    virtual void cleanupBuild(bool force);
+
+public:
 
     void killSandbox(bool getStats) override;