the matching result of boost regex match algorithm is different from "grep -P" and pcre2

[zhangyiru]

three regex match algorithm results is following:
the first pattern string is "(a((?0)( ))?+)?+(SKIP) ?(?1)?".
By replacing "?1" with "(a((?0)( ))?+)", we get the second pattern string that is "(a((?0)( ))?+)?+(SKIP) ?((a((?0)( ))?+))?"
the text string both is " aa " ，space before and after "aa".

1.boost
(a((?0)( ))?+)?+(SKIP) ?(?1)?
aa
result: assert failed （https://github.com/boostorg/regex/issues/152）

(a((?0)( ))?+)?+(SKIP) ?((a((?0)( ))?+))?
result: not matched

2.pcre2
(a((?0)( ))?+)?+(SKIP) ?(?1)?
aa
result: matched

(a((?0)( ))?+)?+(SKIP) ?((a((?0)( ))?+))?
result: matched

3.grep -P
/root/a.txt include " aa "
grep -P "(a((?0)( ))?+)?+(SKIP) ?(?1)?" /root/a.txt
result: matched

grep -P "(a((?0)( ))?+)?+(SKIP) ?((a((?0)( ))?+))?" /root/a.txt
result: matched

According to three results，pcre2 and "grep -P" can match, so is there a problem with boost regex match algorithm? who knows that , i do not know much about the boost regex.
thanks~

[zhangyiru]

fixed by #165
closed