From 4144d506bbe1b34b17093f5bbeb9135b986492d8 Mon Sep 17 00:00:00 2001
From: Ariadne Conill <ariadne@dereferenced.org>
Date: Wed, 6 Oct 2021 11:48:13 -0600
Subject: [PATCH] implement dependency refcounting

---
 libpkgconf/dependency.c | 52 +++++++++++++++++++++++++++++++++++++----
 libpkgconf/libpkgconf.h |  5 ++++
 2 files changed, 53 insertions(+), 4 deletions(-)

diff --git a/libpkgconf/dependency.c b/libpkgconf/dependency.c
index 616c0c2..e5b29c2 100644
--- a/libpkgconf/dependency.c
+++ b/libpkgconf/dependency.c
@@ -92,7 +92,7 @@ add_or_replace_dependency_node(const pkgconf_client_t *client, pkgconf_dependenc
 		{
 			PKGCONF_TRACE(client, "dropping dependency [%s]@%p because of collision", depbuf, dep);
 
-			free(dep);
+			pkgconf_dependency_unref(dep->owner, dep);
 			return NULL;
 		}
 		else if (dep2->flags && dep->flags == 0)
@@ -100,7 +100,7 @@ add_or_replace_dependency_node(const pkgconf_client_t *client, pkgconf_dependenc
 			PKGCONF_TRACE(client, "dropping dependency [%s]@%p because of collision", depbuf2, dep2);
 
 			pkgconf_node_delete(&dep2->iter, list);
-			free(dep2);
+			pkgconf_dependency_unref(dep2->owner, dep2);
 		}
 		else
 			/* If both dependencies have equal strength, we keep both, because of situations like:
@@ -115,7 +115,7 @@ add_or_replace_dependency_node(const pkgconf_client_t *client, pkgconf_dependenc
 	PKGCONF_TRACE(client, "added dependency [%s] to list @%p; flags=%x", dependency_to_str(dep, depbuf, sizeof depbuf), list, dep->flags);
 	pkgconf_node_insert_tail(&dep->iter, dep, list);
 
-	return dep;
+	return pkgconf_dependency_ref(dep->owner, dep);
 }
 
 static inline pkgconf_dependency_t *
@@ -131,6 +131,8 @@ pkgconf_dependency_addraw(const pkgconf_client_t *client, pkgconf_list_t *list,
 
 	dep->compare = compare;
 	dep->flags = flags;
+	dep->owner = client;
+	dep->refcount = 0;
 
 	return add_or_replace_dependency_node(client, dep, list);
 }
@@ -202,6 +204,48 @@ pkgconf_dependency_free_one(pkgconf_dependency_t *dep)
 	free(dep);
 }
 
+/*
+ * !doc
+ *
+ * .. c:function:: pkgconf_dependency_t *pkgconf_dependency_ref(pkgconf_client_t *owner, pkgconf_dependency_t *dep)
+ *
+ *    Increases a dependency node's refcount.
+ *
+ *    :param pkgconf_client_t* owner: The client object which owns the memory of this dependency node.
+ *    :param pkgconf_dependency_t* dep: The dependency to increase the refcount of.
+ *    :return: the dependency node on success, else NULL
+ */
+pkgconf_dependency_t *
+pkgconf_dependency_ref(pkgconf_client_t *client, pkgconf_dependency_t *dep)
+{
+	if (client != dep->owner)
+		return NULL;
+
+	dep->refcount++;
+	return dep;
+}
+
+/*
+ * !doc
+ *
+ * .. c:function:: void pkgconf_dependency_unref(pkgconf_client_t *owner, pkgconf_dependency_t *dep)
+ *
+ *    Decreases a dependency node's refcount and frees it if necessary.
+ *
+ *    :param pkgconf_client_t* owner: The client object which owns the memory of this dependency node.
+ *    :param pkgconf_dependency_t* dep: The dependency to decrease the refcount of.
+ *    :return: nothing
+ */
+void
+pkgconf_dependency_unref(pkgconf_client_t *client, pkgconf_dependency_t *dep)
+{
+	if (client != dep->owner)
+		return;
+
+	if (--dep->refcount <= 0)
+		pkgconf_dependency_free_one(dep);
+}
+
 /*
  * !doc
  *
@@ -222,7 +266,7 @@ pkgconf_dependency_free(pkgconf_list_t *list)
 		pkgconf_dependency_t *dep = node->data;
 
 		pkgconf_node_delete(&dep->iter, list);
-		pkgconf_dependency_free_one(dep);
+		pkgconf_dependency_unref(dep->owner, dep);
 	}
 }
 
diff --git a/libpkgconf/libpkgconf.h b/libpkgconf/libpkgconf.h
index d0f5f3d..9ee5e30 100644
--- a/libpkgconf/libpkgconf.h
+++ b/libpkgconf/libpkgconf.h
@@ -100,6 +100,9 @@ struct pkgconf_dependency_ {
 	pkgconf_pkg_t *match;
 
 	unsigned int flags;
+
+	int refcount;
+	pkgconf_client_t *owner;
 };
 
 struct pkgconf_tuple_ {
@@ -322,6 +325,8 @@ PKGCONF_API void pkgconf_dependency_append(pkgconf_list_t *list, pkgconf_depende
 PKGCONF_API void pkgconf_dependency_free(pkgconf_list_t *list);
 PKGCONF_API void pkgconf_dependency_free_one(pkgconf_dependency_t *dep);
 PKGCONF_API pkgconf_dependency_t *pkgconf_dependency_add(const pkgconf_client_t *client, pkgconf_list_t *list, const char *package, const char *version, pkgconf_pkg_comparator_t compare, unsigned int flags);
+PKGCONF_API pkgconf_dependency_t *pkgconf_dependency_ref(pkgconf_client_t *client, pkgconf_dependency_t *dep);
+PKGCONF_API void pkgconf_dependency_unref(pkgconf_client_t *client, pkgconf_dependency_t *dep);
 
 /* argvsplit.c */
 PKGCONF_API int pkgconf_argv_split(const char *src, int *argc, char ***argv);