unicorn/qemu/qapi
Eric Blake 2f42c2c195
qapi: Change visit_type_FOO() to no longer return partial objects
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).

Backports commit 68ab47e4b4ecc1c4649362b8cc1e49794d1a6537 from qemu
2018-02-23 19:53:17 -05:00
..
common.json qapi: Add alias for ErrorClass 2018-02-19 20:38:51 -05:00
Makefile.objs remove glib dependency by provide compatible replacements 2016-12-18 14:56:58 -08:00
qapi-dealloc-visitor.c qapi: Simplify semantics of visit_next_list() 2018-02-23 19:50:26 -05:00
qapi-visit-core.c qapi: Change visit_type_FOO() to no longer return partial objects 2018-02-23 19:53:17 -05:00
qmp-input-visitor.c qapi: Simplify semantics of visit_next_list() 2018-02-23 19:50:26 -05:00
qmp-output-visitor.c qapi: Simplify semantics of visit_next_list() 2018-02-23 19:50:26 -05:00
string-input-visitor.c qapi: Simplify semantics of visit_next_list() 2018-02-23 19:50:26 -05:00