Luiz Capitulino <lcapitul...@redhat.com> writes: > On Fri, 19 Jul 2013 04:57:51 -0600 > Eric Blake <ebl...@redhat.com> wrote: > >> On 07/18/2013 08:36 PM, Pawit Pornkitprasan wrote: >> > The qmp_migrate method uses the 'blk' and 'inc' parameter without >> > checking if they're valid or not (they may be uninitialized if >> > command is received via QMP) >> > >> > Signed-off-by: Pawit Pornkitprasan <p.pa...@gmail.com> >> > --- >> > migration.c | 4 ++-- >> > 1 file changed, 2 insertions(+), 2 deletions(-) >> >> Reviewed-by: Eric Blake <ebl...@redhat.com> >> >> However, wouldn't it be nice if we improved the qapi generator to >> guarantee a sane default value for optional parameters, even when >> has_value is false? > > We could do that for bool and pointers, but this wouldn't help > integers and enums. Also, even if we had default values, I guess > I'd enforce a common idiom for handling optionals as this is also > a good practice for preventing bugs.
I disagree on pointers. "have_ptr && ptr->..." is a stupid idiom. The common idiom for safe dereference is "ptr && ptr->...". "bool have_ptr, FOO *ptr" in a parameter list is unidiomatic C. Idiomatic is just "FOO *ptr". Conciseness is a virtue. For non-pointers, there's no special "don't have one" value, so we'd have to declare a default value in the schema to get rid of the have_FOO.
