From cc7b8e0b5ec39d4e29c9dc3062efa3a45c76eca2 Mon Sep 17 00:00:00 2001
From: Mike Pilgrem <mpilgrem@users.noreply.github.com>
Date: Wed, 10 Jun 2026 23:35:27 +0100
Subject: [PATCH] Fix #6931 Use absolute builddir with withCabal

---
 ChangeLog.md                  | 3 +++
 src/Stack/Build/ExecuteEnv.hs | 4 ++--
 2 files changed, 5 insertions(+), 2 deletions(-)

diff --git a/ChangeLog.md b/ChangeLog.md
index 7dbc1f1d34..06e321580f 100644
--- a/ChangeLog.md
+++ b/ChangeLog.md
@@ -22,6 +22,9 @@ Other enhancements:
 
 Bug fixes:
 
+* On Windows, Stack's `build` command now accepts a build directory that is a
+  long path.
+
 ##  v3.11.1 - 2026-05-30
 
 **Changes since v3.9.3:**
diff --git a/src/Stack/Build/ExecuteEnv.hs b/src/Stack/Build/ExecuteEnv.hs
index 8114ce5812..5ae611b9bb 100644
--- a/src/Stack/Build/ExecuteEnv.hs
+++ b/src/Stack/Build/ExecuteEnv.hs
@@ -732,7 +732,7 @@ withSingleContext
           , keepGhcRts = False
           }
     menv <- liftIO $ config.processContextSettings envSettings
-    distRelativeDir' <- distRelativeDir
+    distDir' <- distDirFromDir pkgDir
     setupexehs <-
       -- Avoid broken Setup.hs files causing problems for simple build
       -- types, see:
@@ -913,7 +913,7 @@ withSingleContext
                   <> cabalPackageArg
 
           setupArgs =
-            ("--builddir=" ++ toFilePathNoTrailingSep distRelativeDir') : args
+            ("--builddir=" ++ toFilePathNoTrailingSep distDir') : args
 
           depToMungedPkgNames ::
                PackageName