From 3e67484ef38a7c13619ea44f18047644d8f49dca Mon Sep 17 00:00:00 2001 From: ph10 Date: Sun, 23 Oct 2016 15:43:42 +0000 Subject: [PATCH] Document current assert capture limitation. MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit git-svn-id: svn://vcs.exim.org/pcre2/code/trunk@575 6239d852-aaf2-0410-a92c-79f79f948069 Petr Písař: Ported to 10.22. Signed-off-by: Petr Písař --- doc/pcre2pattern.3 | 7 +++++++ 1 file changed, 7 insertions(+) diff --git a/doc/pcre2pattern.3 b/doc/pcre2pattern.3 index 57b0014..3ca1088 100644 --- a/doc/pcre2pattern.3 +++ b/doc/pcre2pattern.3 @@ -2219,6 +2219,13 @@ numbering the capturing subpatterns in the whole pattern. However, substring capturing is carried out only for positive assertions. (Perl sometimes, but not always, does do capturing in negative assertions.) .P +WARNING: If a positive assertion containing one or more capturing subpatterns +succeeds, but failure to match later in the pattern causes backtracking over +this assertion, the captures within the assertion are reset only if no higher +numbered captures are already set. This is, unfortunately, a fundamental +limitation of the current implementation; it may get removed in a future +reworking. +.P For compatibility with Perl, most assertion subpatterns may be repeated; though it makes no sense to assert the same thing several times, the side effect of capturing parentheses may occasionally be useful. However, an assertion that -- 2.7.4