Il mar 21 gen 2020, 15:22 Markus Armbruster <
address@hidden> 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.