On Thu, Apr 20, 2023 at 07:29:27PM +0200, Alejandro Colomar wrote:
> On 4/20/23 17:35, наб wrote:
> > --- a/man3/regex.3
> > +++ b/man3/regex.3
> > @@ -131,23 +131,30 @@ .SS Matching
> > above).
> > .TP
> > .B REG_STARTEND
> > -Use
> > -.I pmatch[0]
> > -on the input string, starting at byte
> > -.I pmatch[0].rm_so
> > -and ending before byte
> > -.IR pmatch[0].rm_eo .
> > +Match
> > +.RI [ string " + " pmatch[0].rm_so ", " string " + " pmatch[0].rm_eo )
> > +instead of
> > +.RI [ string ", " string " + \fBstrlen\fP(" string )).
> > This allows matching embedded NUL bytes
> > and avoids a
> > .BR strlen (3)
> > -on large strings.
> > -It does not use
> > +on known-length strings.
> > +.I pmatch
> > +must point to a valid readable object.
> I think this is redundant, since we showed that [0] is accessed by
> the function.
Yeah.
> > +If any matches are returned
> > +.RB ( REG_NOSUB
> > +wasn't passed to
> > +.BR regcomp (),
> > +the match succeeded, and
> > .I nmatch
> > -on input, and does not change
> > -.B REG_NOTBOL
> > -or
> > -.B REG_NEWLINE
> > -processing.
> > +> 0), they overwrite
> And of course, nmatch must be at least 1, since otherwise, [0] was
> not valid, and the whole call would have been UB; right? So that
> third condition must be true to not invoke UB, so we can omit it too,
> I think.
What? idk where you got this from.
Per 0d120a3c76b4446b194a54387ce0e7a84b208bfd:
In the regexec() signature
regmatch_t pmatch[restrict .nmatch],
is a simplification. It's actually
regmatch_t pmatch[restrict
((.preg->flags & REG_NOSUB) ? 0 : .nmatch) ?:
!!(.eflags & REG_STARTEND)],
If REG_STARTEND, pmatch must point to a valid readable object.
(Naturally, if you pass in uninitialised memory or a null pointer,
then you get UB.)
nmatch is not consulted and has no bearing on this.
Best,
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