core: release the context device list when the context is deleted.

This commit fixes a memory leak in the context list patch. Devices need
to be unref'd when the context is deleted. This can happen if either 1)
the backend init fails, or 2) the context is destroyed by libusb_exit().

libusb/core.c

@@ -1668,6 +1668,7 @@ void API_EXPORTED libusb_set_debug(libusb_context *ctx, int level)
  */
 int API_EXPORTED libusb_init(libusb_context **context)
 {
+	struct libusb_device *dev, *next;
 	char *dbg = getenv("LIBUSB_DEBUG");
 	struct libusb_context *ctx;
 	static int first_init = 1;
@@ -1731,21 +1732,27 @@ int API_EXPORTED libusb_init(libusb_context **context)
 	}
 	usbi_mutex_static_unlock(&default_context_lock);
 
-        usbi_mutex_static_lock(&active_contexts_lock);
-        if (first_init) {
-                first_init = 0;
-                list_init (&active_contexts_list);
-        }
+	usbi_mutex_static_lock(&active_contexts_lock);
+	if (first_init) {
+		first_init = 0;
+		list_init (&active_contexts_list);
+	}
 
-        list_add (&ctx->list, &active_contexts_list);
-        usbi_mutex_static_unlock(&active_contexts_lock);
+	list_add (&ctx->list, &active_contexts_list);
+	usbi_mutex_static_unlock(&active_contexts_lock);
 
 	return 0;
 
 err_destroy_mutex:
 	usbi_mutex_destroy(&ctx->open_devs_lock);
 	usbi_mutex_destroy(&ctx->usb_devs_lock);
 err_free_ctx:
+	usbi_mutex_lock(&ctx->usb_devs_lock);
+	list_for_each_entry_safe(dev, next, &ctx->usb_devs, list, struct libusb_device) {
+		list_del(&dev->list);
+		libusb_unref_device(dev);
+	}
+	usbi_mutex_unlock(&ctx->usb_devs_lock);
 	free(ctx);
 err_unlock:
 	usbi_mutex_static_unlock(&default_context_lock);
@@ -1759,6 +1766,8 @@ int API_EXPORTED libusb_init(libusb_context **context)
  */
 void API_EXPORTED libusb_exit(struct libusb_context *ctx)
 {
+	struct libusb_device *dev, *next;
+
 	usbi_dbg("");
 	USBI_GET_CONTEXT(ctx);
 
@@ -1776,12 +1785,19 @@ void API_EXPORTED libusb_exit(struct libusb_context *ctx)
 		usbi_mutex_static_unlock(&default_context_lock);
 	}
 
-        usbi_mutex_static_lock(&active_contexts_lock);
-        list_del (&ctx->list);
-        usbi_mutex_static_unlock(&active_contexts_lock);
+	usbi_mutex_static_lock(&active_contexts_lock);
+	list_del (&ctx->list);
+	usbi_mutex_static_unlock(&active_contexts_lock);
 
 	usbi_hotplug_deregister_all(ctx);
 
+	usbi_mutex_lock(&ctx->usb_devs_lock);
+	list_for_each_entry_safe(dev, next, &ctx->usb_devs, list, struct libusb_device) {
+		list_del(&dev->list);
+		libusb_unref_device(dev);
+	}
+	usbi_mutex_unlock(&ctx->usb_devs_lock);
+
 	/* a little sanity check. doesn't bother with open_devs locking because
 	 * unless there is an application bug, nobody will be accessing this. */
 	if (!list_empty(&ctx->open_devs))