Il mar 21 gen 2020, 15:22 Markus Armbruster <arm...@redhat.com> ha scritto:
> > To see it a different way, these are the "C bindings" to QMP, just that
> > the implementation is an in-process call rather than RPC. If the QAPI
> > code generator was also able to generate Python bindings and the like,
> > they would have to be the same for all QEMU binaries, wouldn't they?
>
> Ommitting the kind of #if we've been discussing is relatively harmless
> but what about this one, in qapi-types-block-core.h:
>
> typedef enum BlockdevDriver {
> BLOCKDEV_DRIVER_BLKDEBUG,
> [...]
> #if defined(CONFIG_REPLICATION)
> BLOCKDEV_DRIVER_REPLICATION,
> #endif /* defined(CONFIG_REPLICATION) */
> [...]
> BLOCKDEV_DRIVER__MAX,
> } BlockdevDriver;
>
Well, I don't think this should be conditional at all. Introspection is a
tool to detect unsupported features, not working features. KVM will be
present in introspection data even if /dev/kvm doesn't exist on your
machine or you don't have permission to access it. I would restrict very
much #if usage in QAPI to the very minimum necessary.
Paolo
> If I omit it in the header, I then have to omit it in
> qapi-types-block-core.c's
>
> const QEnumLookup BlockdevDriver_lookup = {
> .array = (const char *const[]) {
> [BLOCKDEV_DRIVER_BLKDEBUG] = "blkdebug",
> [...]
> #if defined(CONFIG_REPLICATION)
> [BLOCKDEV_DRIVER_REPLICATION] = "replication",
> #endif /* defined(CONFIG_REPLICATION) */
> [...]
> },
> .size = BLOCKDEV_DRIVER__MAX
> };
>
> and God knows what else. But I must not omit it in qapi-introspect.c's
>
> QLIT_QDICT(((QLitDictEntry[]) {
> { "meta-type", QLIT_QSTR("enum"), },
> { "name", QLIT_QSTR("245"), },
> { "values", QLIT_QLIST(((QLitObject[]) {
> QLIT_QSTR("blkdebug"),
> [...]
> #if defined(CONFIG_REPLICATION)
> QLIT_QSTR("replication"),
> #endif /* defined(CONFIG_REPLICATION) */
> [...]
> {}
> })), },
> {}
> })),
>
> because that would defeat introspection.
>
> I smell a swamp.
>
> I'd rather not complicate the generator to support not including a
> header I feel we *should* include. #ifdef CONFIG_FOO can occur not just
> in QAPI-generated code, and neglecting to include the relevant header
> can cause *nasty* problems not just in QAPI-generated code. Like
> inconsistent struct definitions in separate compilation units. Been
> there, debugged that, wasn't fun, do not want to go there again.
>
>
