Re: [PATCH v4 6/6] regex.3: Destandardeseify Match offsets

[Alejandro Colomar <alx.manpages@gmail.com>]

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On 4/20/23 15:02, наб wrote:
> This section reads like it were (and pretty much is) lifted from POSIX.
> That's hard to read, because POSIX is horrendously verbose, as usual.
> 
> Instead, synopsise it into something less formal but more reasonable,
> and describe the resulting range with a range instead of a paragraph.
> 
> Signed-off-by: Ahelenia Ziemiańska <nabijaczleweli@nabijaczleweli.xyz>
> ---
>  man3/regex.3 | 53 +++++++++++++++++++++++++---------------------------
>  1 file changed, 25 insertions(+), 28 deletions(-)
> 
> diff --git a/man3/regex.3 b/man3/regex.3
> index 6d203fa22..552763940 100644
> --- a/man3/regex.3
> +++ b/man3/regex.3
> @@ -188,37 +188,34 @@ This flag is a BSD extension, not present in POSIX.
>  .SS Match offsets
>  Unless
>  .B REG_NOSUB
> -was set for the compilation of the pattern buffer, it is possible to
> -obtain match addressing information.
> -.I pmatch
> -must be dimensioned to have at least
> -.I nmatch
> -elements.
> -These are filled in by
> +was passed to
> +.BR regcomp (),
> +it is possible to
> +obtain the locations of matches within
> +.IR string :
>  .BR regexec ()
> -with substring match addresses.
> -The offsets of the subexpression starting at the
> -.IR i th
> -open parenthesis are stored in
> -.IR pmatch[i] .
> -The entire regular expression's match addresses are stored in
> -.IR pmatch[0] .
> -(Note that to return the offsets of
> -.I N
> -subexpression matches,
> +fills
>  .I nmatch
> -must be at least
> -.IR N+1 .)
> -Any unused structure elements will contain the value \-1.
> +elements of
> +.I pmatch
> +with results:
> +.I pmatch[0]
> +corresponds to the entire match,

I still don't understand this.  Does REG_NOSUB also affect pmatch[0]?
I would have expected that it would only affect *sub*matches, that is, [>0].

> +.I pmatch[1]
> +to the first expression, etc.
> +If there were more matches than
> +.IR nmatch ,
> +they are discarded;
> +if fewer,
> +unused elements of
> +.I pmatch
> +are filled with
> +.BR \-1 s.
>  .PP
> -Each
> -.I rm_so
> -element that is not \-1 indicates the start offset of the next largest
> -substring match within the string.
> -The relative
> -.I rm_eo
> -element indicates the end offset of the match,
> -which is the offset of the first character after the matching text.
> +Each returned valid
> +.RB (non- \-1 )
> +match corresponds to the range
> +.RI [ string " + " rm_so ", " string " + " rm_eo ).
>  .PP
>  .I regoff_t
>  is a signed integer type

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