mirror of https://github.com/proxmox/mirror_qemu
![]() Returning a partial object on error is an invitation for a careless caller to leak memory. We already fixed things in an earlier patch to guarantee NULL if visit_start fails ("qapi: Guarantee NULL obj on input visitor callback error"), but that does not help the case where visit_start succeeds but some other failure happens before visit_end, such that we leak a partially constructed object outside visit_type_FOO(). As no one outside the testsuite was actually relying on these semantics, it is cleaner to just document and guarantee that ALL pointer-based visit_type_FOO() functions always leave a safe value in *obj during an input visitor (either the new object on success, or NULL if an error is encountered), so callers can now unconditionally use qapi_free_FOO() to clean up regardless of whether an error occurred. The decision is done by adding visit_is_input(), then updating the generated code to check if additional cleanup is needed based on the type of visitor in use. Note that we still leave *obj unchanged after a scalar-based visit_type_FOO(); I did not feel like auditing all uses of visit_type_Enum() to see if the callers would tolerate a specific sentinel value (not to mention having to decide whether it would be better to use 0 or ENUM__MAX as that sentinel). Signed-off-by: Eric Blake <eblake@redhat.com> Message-Id: <1461879932-9020-25-git-send-email-eblake@redhat.com> Signed-off-by: Markus Armbruster <armbru@redhat.com> |
||
---|---|---|
.. | ||
qmp | ||
dealloc-visitor.h | ||
error.h | ||
opts-visitor.h | ||
qmp-event.h | ||
qmp-input-visitor.h | ||
qmp-output-visitor.h | ||
string-input-visitor.h | ||
string-output-visitor.h | ||
util.h | ||
visitor-impl.h | ||
visitor.h |