From patchwork Thu Jul 23 14:01:35 2015 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Markus Armbruster X-Patchwork-Id: 499424 Return-Path: X-Original-To: incoming@patchwork.ozlabs.org Delivered-To: patchwork-incoming@bilbo.ozlabs.org Received: from lists.gnu.org (lists.gnu.org [IPv6:2001:4830:134:3::11]) (using TLSv1 with cipher AES256-SHA (256/256 bits)) (No client certificate requested) by ozlabs.org (Postfix) with ESMTPS id 9C735140D30 for ; Fri, 24 Jul 2015 00:05:20 +1000 (AEST) Received: from localhost ([::1]:41513 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ZIH7e-00068f-Q6 for incoming@patchwork.ozlabs.org; Thu, 23 Jul 2015 10:05:18 -0400 Received: from eggs.gnu.org ([2001:4830:134:3::10]:33360) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ZIH4I-0008Il-C0 for qemu-devel@nongnu.org; Thu, 23 Jul 2015 10:01:56 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1ZIH4A-0004b4-41 for qemu-devel@nongnu.org; Thu, 23 Jul 2015 10:01:50 -0400 Received: from mx1.redhat.com ([209.132.183.28]:60771) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ZIH49-0004an-VY for qemu-devel@nongnu.org; Thu, 23 Jul 2015 10:01:42 -0400 Received: from int-mx14.intmail.prod.int.phx2.redhat.com (int-mx14.intmail.prod.int.phx2.redhat.com [10.5.11.27]) by mx1.redhat.com (Postfix) with ESMTPS id D20733708C4 for ; Thu, 23 Jul 2015 14:01:40 +0000 (UTC) Received: from blackfin.pond.sub.org (ovpn-116-26.ams2.redhat.com [10.36.116.26]) by int-mx14.intmail.prod.int.phx2.redhat.com (8.14.4/8.14.4) with ESMTP id t6NE1dXQ006420 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=NO); Thu, 23 Jul 2015 10:01:40 -0400 Received: by blackfin.pond.sub.org (Postfix, from userid 1000) id B9736305D0F4; Thu, 23 Jul 2015 16:01:38 +0200 (CEST) From: Markus Armbruster To: qemu-devel@nongnu.org Date: Thu, 23 Jul 2015 16:01:35 +0200 Message-Id: <1437660098-4584-5-git-send-email-armbru@redhat.com> In-Reply-To: <1437660098-4584-1-git-send-email-armbru@redhat.com> References: <1437660098-4584-1-git-send-email-armbru@redhat.com> X-Scanned-By: MIMEDefang 2.68 on 10.5.11.27 X-detected-operating-system: by eggs.gnu.org: GNU/Linux 3.x X-Received-From: 209.132.183.28 Cc: pbonzini@redhat.com, dgilbert@redhat.com, lersek@redhat.com, mst@redhat.com Subject: [Qemu-devel] [PATCH v2 4/7] qga/vss-win32: Document the DLL requires non-null errp X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.14 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org Sender: qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org requester.cpp uses this pattern to receive an error and pass it on to the caller (err_is_set() macro peeled off for clarity): ... code that may set errset->errp ... if (errset->errp && *errset->errp) { ... handle error ... } This breaks when errset->errp is null. As far as I can tell, it currently isn't, so this is merely fragile, not actually broken. The robust way to do this is to receive the error in a local variable, then propagate it up, like this: Error *err = NULL; ... code that may set err ... if (err) ... handle error ... error_propagate(errset->errp, err); } See also commit 5e54769, 0f230bf, a903f40. Signed-off-by: Markus Armbruster Reviewed-by: Eric Blake --- qga/vss-win32.c | 1 + qga/vss-win32/requester.cpp | 3 ++- qga/vss-win32/requester.h | 2 +- 3 files changed, 4 insertions(+), 2 deletions(-) diff --git a/qga/vss-win32.c b/qga/vss-win32.c index e1f5398..d75d7bb 100644 --- a/qga/vss-win32.c +++ b/qga/vss-win32.c @@ -154,6 +154,7 @@ void qga_vss_fsfreeze(int *nr_volume, Error **errp, bool freeze) .errp = errp, }; + g_assert(errp); /* requester.cpp requires it */ func = (QGAVSSRequesterFunc)GetProcAddress(provider_lib, func_name); if (!func) { error_setg_win32(errp, GetLastError(), "failed to load %s from %s", diff --git a/qga/vss-win32/requester.cpp b/qga/vss-win32/requester.cpp index b130fee..aae0d5f 100644 --- a/qga/vss-win32/requester.cpp +++ b/qga/vss-win32/requester.cpp @@ -25,8 +25,9 @@ #define err_set(e, err, fmt, ...) \ ((e)->error_setg_win32((e)->errp, err, fmt, ## __VA_ARGS__)) +/* Bad idea, works only when (e)->errp != NULL: */ #define err_is_set(e) ((e)->errp && *(e)->errp) - +/* To lift this restriction, error_propagate(), like we do in QEMU code */ /* Handle to VSSAPI.DLL */ static HMODULE hLib; diff --git a/qga/vss-win32/requester.h b/qga/vss-win32/requester.h index 0a8d048..34be5c1 100644 --- a/qga/vss-win32/requester.h +++ b/qga/vss-win32/requester.h @@ -27,7 +27,7 @@ typedef void (*ErrorSetFunc)(struct Error **errp, int win32_err, const char *fmt, ...) GCC_FMT_ATTR(3, 4); typedef struct ErrorSet { ErrorSetFunc error_setg_win32; - struct Error **errp; + struct Error **errp; /* restriction: must not be null */ } ErrorSet; STDAPI requester_init(void);