From 3e6b74043020d0838f739f144fac4f14828ae429 Mon Sep 17 00:00:00 2001
From: "Emil J. Tywoniak" <emil@tywoniak.eu>
Date: Sun, 21 Dec 2025 16:56:14 +0100
Subject: [PATCH] rtlil: allow friends to use Cell constructors with a factory
 token pattern

---
 kernel/rtlil.cc          | 4 ++--
 kernel/rtlil.h           | 8 +++++---
 kernel/unstable/patch.cc | 2 +-
 3 files changed, 8 insertions(+), 6 deletions(-)

diff --git a/kernel/rtlil.cc b/kernel/rtlil.cc
index 5a3a5fb60..ac970e2f1 100644
--- a/kernel/rtlil.cc
+++ b/kernel/rtlil.cc
@@ -3129,7 +3129,7 @@ RTLIL::Wire *RTLIL::Module::addWire(RTLIL::IdString name, const RTLIL::Wire *oth
 
 RTLIL::Cell *RTLIL::Module::addCell(RTLIL::IdString name, RTLIL::IdString type)
 {
-	RTLIL::Cell *cell = new RTLIL::Cell;
+	RTLIL::Cell *cell = new RTLIL::Cell(Cell::ConstructToken{});
 	cell->name = std::move(name);
 	cell->type = type;
 	add(cell);
@@ -4243,7 +4243,7 @@ std::string RTLIL::Process::to_rtlil_str() const
 	return f.str();
 }
 
-RTLIL::Cell::Cell() : module(nullptr)
+RTLIL::Cell::Cell(RTLIL::Cell::ConstructToken) : module(nullptr)
 {
 	static unsigned int hashidx_count = 123456789;
 	hashidx_count = mkhash_xorshift(hashidx_count);
diff --git a/kernel/rtlil.h b/kernel/rtlil.h
index cf43df7f0..6c22efcd5 100644
--- a/kernel/rtlil.h
+++ b/kernel/rtlil.h
@@ -2525,18 +2525,20 @@ struct RTLIL::Memory : public RTLIL::NamedObject
 
 struct RTLIL::Cell : public RTLIL::NamedObject
 {
+private:
+	struct ConstructToken { explicit ConstructToken() = default; };
+public:
 	Hasher::hash_t hashidx_;
 	[[nodiscard]] Hasher hash_into(Hasher h) const { h.eat(hashidx_); return h; }
 
-public:
 	// use module->addCell() and module->remove() to create or destroy cells
 	friend struct RTLIL::Module;
 	friend struct RTLIL::Patch;
-	Cell();
+	Cell(ConstructToken);
 	~Cell();
 
 	// do not simply copy cells
-	Cell(RTLIL::Cell &other) = delete;
+	Cell(ConstructToken, RTLIL::Cell &other);
 	void operator=(RTLIL::Cell &other) = delete;
 
 	RTLIL::Module *module;
diff --git a/kernel/unstable/patch.cc b/kernel/unstable/patch.cc
index 18d761384..53632114d 100644
--- a/kernel/unstable/patch.cc
+++ b/kernel/unstable/patch.cc
@@ -4,7 +4,7 @@ YOSYS_NAMESPACE_BEGIN
 
 using namespace RTLIL;
 Cell* Patch::addCell(IdString name, IdString type) {
-    auto& cell = cells_.emplace_back();
+    auto& cell = cells_.emplace_back(Cell::ConstructToken{});
 	cell.name = std::move(name);
 	cell.type = type;
     return &cell;