On Wed, May 10, 2023 at 01:48:08PM +0200, Laszlo Ersek wrote:
> This is the last wave (wave 5). Line length maxima:
>
> file before after
> ---------------- ------ -----
> lib/states-run.c 102 98
> lib/states.c 116 80
> lib/states.h 123 86
>
> The longest line in "lib/states.h" becomes:
>
> > extern int
> > nbd_internal_enter_STATE_NEWSTYLE_OPT_STRUCTURED_REPLY_RECV_REPLY_PAYLOAD (
> > struct nbd_handle *h, bool *blocked
> > );
>
> The one in "lib/states-run.c":
>
> > case STATE_NEWSTYLE_OPT_STRUCTURED_REPLY_RECV_REPLY_PAYLOAD:
> > r =
> > nbd_internal_enter_STATE_NEWSTYLE_OPT_STRUCTURED_REPLY_RECV_REPLY_PAYLOAD
> > (h, &blocked);
> > break;
>
> We couldn't find a "scalable" approach for shortening these (the state
> machine can be nested indefinitely deeply), so we decided to live with
> them.
For public reference, we considered approaches such as shortening
specific state names:
s/NEWSTYLE/NEW/
s/OPT_STRUCTURED_REPLY/OPT_SR/
s/RECV_REPLY_PAYLOAD/RECV_PAYLOAD/
but the more names we change, the more places we have to touch, and it
doesn't alleviate the possibility of future state names being long.
We also considered a different way of writing state names, by
introducing a series of glue macros, where you can then wrap macro
parameters but still generate a long C identifier, something like:
extern int NBD_GLUE4(nbd_internal_enter_STATE, NEWSTYLE,
OPT_STRUCTURED_REPLY, RECV_REPLY_PAYLOAD) {
...
case NBD_GLUE4(STATE, NEWSTYLE, OPT_STRUCTURED_REPLY,
RECV_REPLY_PAYLOAD):
with variations such as writing a variadic macro NBD_GLUE(...) using
__VA_ARGS__ that then dispatches to the correct NBD_GLUE<n> rather
than having to be explicit about it at callsites. But that hurts
grep'ability when stepping through the state machine in gdb.
>
> Thanks
> Laszlo
> Laszlo Ersek (6):
> state_machine_generator: wrap debug() calls in nbd_internal_run()
> generator/utils: add "pr_wrap_c_comment"
> state_machine_generator: wrap state comments in lib/states.{h,c}
> state_machine_generator: wrap nbd_internal_enter_* prototypes
> state_machine_generator: wrap enter_*() calls and prototypes
> state_machine_generator: rename, and break up the init. of,
> "next_state"
For those without explicit comments,
Reviewed-by: Eric Blake <ebl...@redhat.com>
--
Eric Blake, Principal Software Engineer
Red Hat, Inc. +1-919-301-3266
Virtualization: qemu.org | libvirt.org
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