From 08e64640357cd9517aa30fd49840f05f0f2ee3a4 Mon Sep 17 00:00:00 2001 From: Markus Armbruster Date: Sat, 20 Jun 2015 09:33:56 +0200 Subject: qga/vss-win32: Document the DLL requires non-null errp 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(-) (limited to 'qga') diff --git a/qga/vss-win32.c b/qga/vss-win32.c index e1f539835c..d75d7bbf09 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 b130fee934..aae0d5f2bf 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 0a8d048874..34be5c1d11 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); -- cgit v1.2.3