From a091a8100a8587185e579d4cff04381e8e074f12 Mon Sep 17 00:00:00 2001
From: Sergei Zimmerman <sergei@zimmerman.foo>
Date: Sun, 9 Nov 2025 22:09:18 +0300
Subject: [PATCH] libexpr: Clear PosTable contents in EvalState::resetFileCache

Otherwise PosTable grows indefinitely for each reload. Since
the total input size is limited to 4GB (uint32_t for byte offset PosIdx)
it can get exhausted pretty. This ensures that we don't waste memory
on reloads as well.
---
 src/libexpr/eval.cc                       |  1 +
 src/libutil/include/nix/util/pos-table.hh | 10 ++++++++++
 2 files changed, 11 insertions(+)

diff --git a/src/libexpr/eval.cc b/src/libexpr/eval.cc
index 7036df957..5ddbac634 100644
--- a/src/libexpr/eval.cc
+++ b/src/libexpr/eval.cc
@@ -1113,6 +1113,7 @@ void EvalState::resetFileCache()
     importResolutionCache->clear();
     fileEvalCache->clear();
     inputCache->clear();
+    positions.clear();
 }
 
 void EvalState::eval(Expr * e, Value & v)
diff --git a/src/libutil/include/nix/util/pos-table.hh b/src/libutil/include/nix/util/pos-table.hh
index d944b1353..c5f93a3d5 100644
--- a/src/libutil/include/nix/util/pos-table.hh
+++ b/src/libutil/include/nix/util/pos-table.hh
@@ -111,6 +111,16 @@ public:
             return o->origin;
         return std::monostate{};
     }
+
+    /**
+     * Remove all origins from the table.
+     */
+    void clear()
+    {
+        auto lines = linesCache.lock();
+        lines->clear();
+        origins.clear();
+    }
 };
 
 } // namespace nix