On Thu, May 11, 2023 at 08:45:25AM +0200, Laszlo Ersek wrote:
> On 5/10/23 17:14, Eric Blake wrote:
> > On Wed, May 10, 2023 at 01:48:11PM +0200, Laszlo Ersek wrote:
> >> Wrap those comments in "lib/states.h" and "lib/states.c" that describe the
> >> automaton's states.
> >>
> >> Example changes from "lib/states.h":
> >>
> >>> /* CONNECT_TCP.CONNECT: Initial call to connect(2) on a TCP socket */
> >>> STATE_CONNECT_TCP_CONNECT,
> >>>
> >>> - /* CONNECT_TCP.CONNECTING: Connecting to the remote server over a TCP
> >>> socket */
> >>> + /* CONNECT_TCP.CONNECTING: Connecting to the remote server over a TCP
> >>> socket
> >>> + */
> >
> > This one looks a bit unusual; I didn't find any instances of this
> > style in existing hand-written comments (
> > git grep -B1 '^[:space:]*\*/$' | grep '/\*'
> This comment folding style (breaking off just the terminating '*/') is
> common at least in QEMU, as I recall:
>
> git grep -h -B1 '^ *\*/$' | grep -A1 '^ */\*'
>
> ... The same command also returns 5 hits in libnbd:
>
> > /* Return true if size is a multiple of align. align must be power of 2.
> > */
Oops, you proved me wrong.
>
> Interestingly, your variant of the same grep does not produce any
> output, and I don't immediately see why...
>
> Ah, I see now. Character classes such as [:space:] *only* work within
> bracket expressions. POSIX writes:
>
> The character sequences "[.", "[=", and "[:" ( <left-square-bracket>
> followed by a <period>, <equals-sign>, or <colon>) shall be special
> inside a bracket expression and are used to delimit collating
> symbols, equivalence class expressions, and character class
> expressions. These symbols shall be followed by a valid expression
> and the matching terminating sequence ".]", "=]", or ":]", as
> described in the following items.
>
> In other words, the sequence "[:space:]" in itself is just a (weird)
> bracket expression, matching the 's', 'p', 'a', 'c', 'e', and ':'
> (twice) characters.
Yeah, and I should know that. There is an exception ("tr '[:alpha:]"
... is allowed to operate on a character class without needing a
bracket expression, since it is not parsing a regex in the first
place), but I was indeed typing too fast and messed up on my grep.
>
> If we want [:space:] to function as a character class, it must be
> embedded inside a bracket expression. So the following works:
>
> git grep -B1 '^[[:space:]]*\*/$' | grep '/\*'
>
> (And then this form allows for other expressions alongside the character
> class within the bracket expression -- for example, *further* character
> classes.)
>
> In fact this is the first time I've myself ever understood how character
> classes are supposed to be used in grep :/
Not my first time, but obviously something I don't do frequently
enough that I still tend to forget it.
--
Eric Blake, Principal Software Engineer
Red Hat, Inc. +1-919-301-3266
Virtualization: qemu.org | libvirt.org
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