From mboxrd@z Thu Jan 1 00:00:00 1970 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) From: Markus Armbruster 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> Subject: [Qemu-devel] [PATCH v2 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 Cc: pbonzini@redhat.com, dgilbert@redhat.com, lersek@redhat.com, mst@redhat.com 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); -- 1.9.3