From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:41445) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Za1xt-0006AJ-1r for qemu-devel@nongnu.org; Thu, 10 Sep 2015 09:32:37 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1Za1xn-0005Dw-Bs for qemu-devel@nongnu.org; Thu, 10 Sep 2015 09:32:36 -0400 Received: from mx1.redhat.com ([209.132.183.28]:53473) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Za1xn-0005Dc-7G for qemu-devel@nongnu.org; Thu, 10 Sep 2015 09:32:31 -0400 Received: from int-mx13.intmail.prod.int.phx2.redhat.com (int-mx13.intmail.prod.int.phx2.redhat.com [10.5.11.26]) by mx1.redhat.com (Postfix) with ESMTPS id EE13B341AC6 for ; Thu, 10 Sep 2015 13:32:30 +0000 (UTC) Received: from blackfin.pond.sub.org (ovpn-116-61.ams2.redhat.com [10.36.116.61]) by int-mx13.intmail.prod.int.phx2.redhat.com (8.14.4/8.14.4) with ESMTP id t8ADWTvD030248 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=NO) for ; Thu, 10 Sep 2015 09:32:30 -0400 From: Markus Armbruster Date: Thu, 10 Sep 2015 15:32:25 +0200 Message-Id: <1441891948-28169-5-git-send-email-armbru@redhat.com> In-Reply-To: <1441891948-28169-1-git-send-email-armbru@redhat.com> References: <1441891948-28169-1-git-send-email-armbru@redhat.com> Subject: [Qemu-devel] [PULL 4/7] qga/vss-win32: Document the DLL requires non-null errp List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-devel@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); -- 2.4.3