From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:54465) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ZVMnD-0008Ki-MX for qemu-devel@nongnu.org; Fri, 28 Aug 2015 12:46:22 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1ZVMn7-0000Lv-VI for qemu-devel@nongnu.org; Fri, 28 Aug 2015 12:46:19 -0400 Received: from mx1.redhat.com ([209.132.183.28]:45130) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ZVMn7-0000Li-Pd for qemu-devel@nongnu.org; Fri, 28 Aug 2015 12:46:13 -0400 From: Markus Armbruster Date: Fri, 28 Aug 2015 18:45:55 +0200 Message-Id: <1440780366-7177-16-git-send-email-armbru@redhat.com> In-Reply-To: <1440780366-7177-1-git-send-email-armbru@redhat.com> References: <1440780366-7177-1-git-send-email-armbru@redhat.com> Subject: [Qemu-devel] [PATCH v2 15/26] qapi: Document shortcoming with union 'data' branch List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-devel@nongnu.org Cc: mdroth@linux.vnet.ibm.com From: Eric Blake Add a FIXME to remind us to fully audit whether removing the 'void *data' branch of each qapi union type can be done safely. Signed-off-by: Eric Blake Message-Id: <1438297637-26789-1-git-send-email-eblake@redhat.com> Signed-off-by: Markus Armbruster --- scripts/qapi-types.py | 8 ++++++++ 1 file changed, 8 insertions(+) diff --git a/scripts/qapi-types.py b/scripts/qapi-types.py index 82141cd..8444f98 100644 --- a/scripts/qapi-types.py +++ b/scripts/qapi-types.py @@ -219,6 +219,14 @@ struct %(name)s ''', discriminator_type_name=c_name(discriminator_type_name)) + # FIXME: What purpose does data serve, besides preventing a union that + # has a branch named 'data'? We use it in qapi-visit.py to decide + # whether to bypass the switch statement if visiting the discriminator + # failed; but since we 0-initialize structs, and cannot tell what + # branch of the union is in use if the discriminator is invalid, there + # should not be any data leaks even without a data pointer. Or, if + # 'data' is merely added to guarantee we don't have an empty union, + # shouldn't we enforce that at .json parse time? ret += mcgen(''' union { /* union tag is @%(c_name)s */ void *data; -- 2.4.3