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 <[email protected]>
Reviewed-by: Eric Blake <[email protected]>
---
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
