From 2ef4b69760af183792a740f425eb371a6aeb0009 Mon Sep 17 00:00:00 2001
From: eldritch horrors <pennae@lix.systems>
Date: Sun, 6 Apr 2025 20:29:25 +0200
Subject: [PATCH] libutil: disallow implicit ref creations

448c7d50e1bfac6644c0cf13085eb1bbeda32e6b was a bit over-eager and didn't
make the `ref(enable_shared_from_this &)` constructor explicit. this has
confused hydra maintainers, and is just generally bad practice since any
reference is allowed to implicitly convert, even if those references are
not associated with an active control block. we can't avoid this problem
entirely, but we can make what happens more explicit by ... well, making
the involved constructor explicit. enable_shared_from_this is statically
unsafe in principle and we really have to get rid of this nonsense soon.

Change-Id: I8b48ef4353e6301b61af3569083f42bc7379b0a4
---
 lix/libexpr/eval-cache.cc          | 2 +-
 lix/libstore/binary-cache-store.cc | 2 +-
 lix/libstore/remote-store.cc       | 2 +-
 lix/libutil/ref.hh                 | 2 +-
 4 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/lix/libexpr/eval-cache.cc b/lix/libexpr/eval-cache.cc
index e4e5dabee..2fb950b77 100644
--- a/lix/libexpr/eval-cache.cc
+++ b/lix/libexpr/eval-cache.cc
@@ -352,7 +352,7 @@ Value * EvalCache::getRootValue(EvalState & state)
 
 ref<AttrCursor> EvalCache::getRoot()
 {
-    return make_ref<AttrCursor>(*this, std::nullopt);
+    return make_ref<AttrCursor>(ref<EvalCache>(*this), std::nullopt);
 }
 
 AttrCursor::AttrCursor(
diff --git a/lix/libstore/binary-cache-store.cc b/lix/libstore/binary-cache-store.cc
index 43872c7cb..f300a44ba 100644
--- a/lix/libstore/binary-cache-store.cc
+++ b/lix/libstore/binary-cache-store.cc
@@ -532,7 +532,7 @@ try {
 
 ref<FSAccessor> BinaryCacheStore::getFSAccessor()
 {
-    return make_ref<RemoteFSAccessor>(*this, config().localNarCache);
+    return make_ref<RemoteFSAccessor>(ref<Store>(*this), config().localNarCache);
 }
 
 kj::Promise<Result<void>>
diff --git a/lix/libstore/remote-store.cc b/lix/libstore/remote-store.cc
index e24c578b7..b3c74ab73 100644
--- a/lix/libstore/remote-store.cc
+++ b/lix/libstore/remote-store.cc
@@ -1022,7 +1022,7 @@ try {
 
 ref<FSAccessor> RemoteStore::getFSAccessor()
 {
-    return make_ref<RemoteFSAccessor>(*this);
+    return make_ref<RemoteFSAccessor>(ref<Store>(*this));
 }
 
 static Logger::Fields readFields(Source & from)
diff --git a/lix/libutil/ref.hh b/lix/libutil/ref.hh
index ab7e60e7b..44858e482 100644
--- a/lix/libutil/ref.hh
+++ b/lix/libutil/ref.hh
@@ -39,7 +39,7 @@ public:
     }
 
     template<std::derived_from<std::enable_shared_from_this<T>> T2>
-    ref(T2 & r) : p(r.shared_from_this())
+    explicit ref(T2 & r) : p(r.shared_from_this())
     {
     }