On 07/20/2017 03:37 PM, Eric Blake wrote: >>> + * @fmt...: QMP message to send to qemu; only recognizes formats >>> + * understood by json-lexer.c >>> * >>> * Sends a QMP message to QEMU and consumes the response. >>> */ >> >> These formats are chosen so that gcc can help us check them. Please add >> GCC_FMT_ATTR(). Precedence: qobject_from_jsonf(). > > Will do. (This patch was originally part of my larger series trying to > get rid of qobject_from_jsonf() - I may still succeed at that, but > separating the easy stuff from the controversial means that the easy > stuff needs tweaking).
Bleargh. It's not that simple.
With printf-style, hmp("literal") and hmp("%s", "literal") produce the
same results.
But with json-lexer style, %s MODIFIES its input.
The original qmp("{'execute':\"foo\"}") sends a JSON object
{'execute':"foo"}
but counterpart qmp("%s", "{'execute':'foo'}") sends a JSON string with
added \ escaping:
"{'execute':\"foo\"}"
So adding the format immediately causes lots of warnings, such as:
CC tests/vhost-user-test.o
tests/vhost-user-test.c: In function ‘test_migrate’:
tests/vhost-user-test.c:668:5: error: format not a string literal and no
format arguments [-Werror=format-security]
rsp = qmp(cmd);
^~~
CC tests/boot-order-test.o
tests/boot-order-test.c: In function ‘test_a_boot_order’:
tests/boot-order-test.c:46:26: error: zero-length gnu_printf format
string [-Werror=format-zero-length]
qmp_discard_response(""); /* HACK: wait for event */
^~
but we CAN'T rewrite those to qmp("%s", command).
Now you can sort-of understand why my larger series wanted to get rid of
qobject_from_jsonf(), since our use of GCC_FMT_ATTR() there is a lie?
--
Eric Blake, Principal Software Engineer
Red Hat, Inc. +1-919-301-3266
Virtualization: qemu.org | libvirt.org
signature.asc
Description: OpenPGP digital signature
