From 022b918db171c9614e7c27f633452fb2bf9e6c57 Mon Sep 17 00:00:00 2001
From: Yorick van Pelt <yorick@yorickvanpelt.nl>
Date: Thu, 27 Jul 2023 15:58:18 +0200
Subject: [PATCH] nix_api_expr: remove bindingsbuilder refcounting

---
 src/libexpr/nix_api_expr_internal.h |  7 ++++++-
 src/libexpr/nix_api_value.cc        | 27 ++++++++++++++-------------
 src/libexpr/nix_api_value.h         | 14 +++++++-------
 3 files changed, 27 insertions(+), 21 deletions(-)

diff --git a/src/libexpr/nix_api_expr_internal.h b/src/libexpr/nix_api_expr_internal.h
index 424ca2874..e9031d311 100644
--- a/src/libexpr/nix_api_expr_internal.h
+++ b/src/libexpr/nix_api_expr_internal.h
@@ -4,7 +4,8 @@
 // forward declaration
 namespace nix {
 class EvalState;
-};
+class BindingsBuilder;
+}; // namespace nix
 
 struct State {
   nix::EvalState state;
@@ -14,4 +15,8 @@ struct GCRef {
   void *ptr;
 };
 
+struct BindingsBuilder {
+  nix::BindingsBuilder builder;
+};
+
 #endif // NIX_API_EXPR_INTERNAL_H
diff --git a/src/libexpr/nix_api_value.cc b/src/libexpr/nix_api_value.cc
index 6a2f19de9..74e8395fc 100644
--- a/src/libexpr/nix_api_value.cc
+++ b/src/libexpr/nix_api_value.cc
@@ -386,16 +386,13 @@ nix_err nix_copy_value(nix_c_context *context, Value *value, Value *source) {
   NIXC_CATCH_ERRS
 }
 
-typedef std::shared_ptr<nix::BindingsBuilder> BindingsBuilder_Inner;
-
 nix_err nix_make_attrs(nix_c_context *context, Value *value,
                        BindingsBuilder *b) {
   if (context)
     context->last_err_code = NIX_OK;
   try {
     auto &v = check_value_not_null(value);
-    nix::BindingsBuilder &builder = **(BindingsBuilder_Inner *)b;
-    v.mkAttrs(builder);
+    v.mkAttrs(b->builder);
   }
   NIXC_CATCH_ERRS
 }
@@ -406,10 +403,11 @@ BindingsBuilder *nix_make_bindings_builder(nix_c_context *context, State *state,
     context->last_err_code = NIX_OK;
   try {
     auto bb = state->state.buildBindings(capacity);
-    auto res = new BindingsBuilder_Inner();
-    *res = std::allocate_shared<nix::BindingsBuilder>(
-        traceable_allocator<nix::BindingsBuilder>(), bb);
-    return res;
+    return new
+#if HAVE_BOEHMGC
+        (NoGC)
+#endif
+            BindingsBuilder{std::move(bb)};
   }
   NIXC_CATCH_ERRS_NULL
 }
@@ -419,14 +417,17 @@ nix_err nix_bindings_builder_insert(nix_c_context *context, BindingsBuilder *b,
   if (context)
     context->last_err_code = NIX_OK;
   try {
-    nix::BindingsBuilder &builder = **(BindingsBuilder_Inner *)b;
     auto &v = check_value_not_null(value);
-    nix::Symbol s = builder.state.symbols.create(name);
-    builder.insert(s, &v);
+    nix::Symbol s = b->builder.state.symbols.create(name);
+    b->builder.insert(s, &v);
   }
   NIXC_CATCH_ERRS
 }
 
-void nix_bindings_builder_unref(BindingsBuilder *bb) {
-  delete (BindingsBuilder_Inner *)bb;
+void nix_bindings_builder_free(BindingsBuilder *bb) {
+#if HAVE_BOEHMGC
+  GC_FREE((nix::BindingsBuilder *)bb);
+#else
+  delete (nix::BindingsBuilder *)bb;
+#endif
 }
diff --git a/src/libexpr/nix_api_value.h b/src/libexpr/nix_api_value.h
index 22ecfa86b..6aae5cf3c 100644
--- a/src/libexpr/nix_api_value.h
+++ b/src/libexpr/nix_api_value.h
@@ -36,11 +36,12 @@ typedef struct State State;
 typedef struct GCRef GCRef;
 // type defs
 /** @brief Stores an under-construction set of bindings
- * Reference-counted
- * @see nix_make_bindings_builder, nix_bindings_builder_unref, nix_make_attrs
+ *
+ * Do not reuse.
+ * @see nix_make_bindings_builder, nix_bindings_builder_free, nix_make_attrs
  * @see nix_bindings_builder_insert
  */
-typedef void BindingsBuilder;
+typedef struct BindingsBuilder BindingsBuilder;
 
 /** @brief PrimOp function
  *
@@ -328,13 +329,12 @@ BindingsBuilder *nix_make_bindings_builder(nix_c_context *context, State *state,
 nix_err nix_bindings_builder_insert(nix_c_context *context,
                                     BindingsBuilder *builder, const char *name,
                                     Value *value);
-/** @brief Unref a bindings builder
+/** @brief Free a bindings builder
  *
  * Does not fail.
- * It'll be deallocated when all references are gone.
- * @param[in] builder the builder to unref
+ * @param[in] builder the builder to free
  */
-void nix_bindings_builder_unref(BindingsBuilder *builder);
+void nix_bindings_builder_free(BindingsBuilder *builder);
 
 // cffi end
 #ifdef __cplusplus