From 11e19ee69027e9e6ed77db2b1b4789afb7848d6a Mon Sep 17 00:00:00 2001
From: Taeer Bar-Yam <taeer.bar-yam@bevuta.com>
Date: Fri, 31 Oct 2025 21:52:10 +0100
Subject: [PATCH] libexpr: shrink ExprWith by 8 bytes

Correct bound on prevWith

Co-authored-by: John Ericson <git@JohnEricson.me>
---
 src/libexpr/include/nix/expr/nixexpr.hh | 2 +-
 src/libexpr/nixexpr.cc                  | 1 +
 2 files changed, 2 insertions(+), 1 deletion(-)

diff --git a/src/libexpr/include/nix/expr/nixexpr.hh b/src/libexpr/include/nix/expr/nixexpr.hh
index fd7ed2a67..1fb4d0642 100644
--- a/src/libexpr/include/nix/expr/nixexpr.hh
+++ b/src/libexpr/include/nix/expr/nixexpr.hh
@@ -637,8 +637,8 @@ struct ExprLet : Expr
 struct ExprWith : Expr
 {
     PosIdx pos;
+    uint32_t prevWith;
     Expr *attrs, *body;
-    size_t prevWith;
     ExprWith * parentWith;
     ExprWith(const PosIdx & pos, Expr * attrs, Expr * body)
         : pos(pos)
diff --git a/src/libexpr/nixexpr.cc b/src/libexpr/nixexpr.cc
index b183f1bbf..81ba5f09f 100644
--- a/src/libexpr/nixexpr.cc
+++ b/src/libexpr/nixexpr.cc
@@ -523,6 +523,7 @@ void ExprWith::bindVars(EvalState & es, const std::shared_ptr<const StaticEnv> &
     prevWith = 0;
     for (curEnv = env.get(), level = 1; curEnv; curEnv = curEnv->up.get(), level++)
         if (curEnv->isWith) {
+            assert(level <= std::numeric_limits<uint32_t>::max());
             prevWith = level;
             break;
         }