qemu-option: qemu_opt_set_bool(): fix code duplication
It will set opt->str in qemu_opt_set_bool, without opt->str, there
will be some potential bugs.
These are uses of opt->str, and what happens when it isn't set:
* qemu_opt_get(): returns NULL, which means "not set". Bug can bite
when value isn't the default value.
* qemu_opt_parse(): passes NULL to parse_option_bool(), which treats it
like "on". Wrong if the value is actually false. Bug can bite when
qemu_opts_validate() runs after qemu_opt_set_bool().
* qemu_opt_del(): passes NULL to g_free(), which is just fine.
* qemu_opt_foreach(): passes NULL to the callback, which is unlikely to
be prepared for it.
* qemu_opts_print(): prints NULL, which crashes on some systems.
* qemu_opts_to_qdict(): passes NULL to qstring_from_str(), which
crashes.
It also makes qemu_opt_set_bool more readable by using find_desc_by_name
and opts_accepts_any.
It is based on Luiz's patch and uses Markus's comments. Discussions can
be found at:
http://lists.nongnu.org/archive/html/qemu-devel/2012-07/msg02716.html
Signed-off-by: Dong Xu Wang <wdongxu@linux.vnet.ibm.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>