Update HTML and plain text documentation

doc/html/README.txt

@@ -271,7 +271,7 @@ library. They are also documented in the pcre2build man page.
   performance in the 8-bit and 16-bit libraries. In the 32-bit library, the
   link size setting is ignored, as 4-byte offsets are always used.
   
-, Lookbehind assertions in which one or more branches can match a variable
+. Lookbehind assertions in which one or more branches can match a variable
   number of characters are supported only if there is a maximum matching length
   for each top-level branch. There is a limit to this maximum that defaults to
   255 characters. You can alter this default by a setting such as
@@ -933,4 +933,4 @@ The distribution should contain the files listed below.
 Philip Hazel
 Email local part: Philip.Hazel
 Email domain: gmail.com
-Last updated: 09 August 2023
+Last updated: 11 August 2023

doc/html/pcre2compat.html

@@ -16,10 +16,10 @@ please consult the man page, in case the conversion went wrong.
 DIFFERENCES BETWEEN PCRE2 AND PERL
 </b><br>
 <P>
-This document describes some of the differences in the ways that PCRE2 and Perl
-handle regular expressions. The differences described here are with respect to
-Perl version 5.34.0, but as both Perl and PCRE2 are continually changing, the
-information may at times be out of date.
+This document describes some of the known differences in the ways that PCRE2
+and Perl handle regular expressions. The differences described here are with
+respect to Perl version 5.34.0, but as both Perl and PCRE2 are continually
+changing, the information may at times be out of date.
 </P>
 <P>
 1. When PCRE2_DOTALL (equivalent to Perl's /s qualifier) is not set, the
@@ -173,59 +173,48 @@ of which (such as named parentheses) were in PCRE2 for some time before. This
 list is with respect to Perl 5.34:
 <br>
 <br>
-(a) Although lookbehind assertions in PCRE2 must match fixed length strings,
-each alternative toplevel branch of a lookbehind assertion can match a
-different length of string. Perl used to require them all to have the same
-length, but the latest version has some variable length support.
-<br>
-<br>
-(b) From PCRE2 10.23, backreferences to groups of fixed length are supported
-in lookbehinds, provided that there is no possibility of referencing a
-non-unique number or name. Perl does not support backreferences in lookbehinds.
-<br>
-<br>
-(c) If PCRE2_DOLLAR_ENDONLY is set and PCRE2_MULTILINE is not set, the $
+(a) If PCRE2_DOLLAR_ENDONLY is set and PCRE2_MULTILINE is not set, the $
 meta-character matches only at the very end of the string.
 <br>
 <br>
-(d) A backslash followed by a letter with no special meaning is faulted. (Perl
+(b) A backslash followed by a letter with no special meaning is faulted. (Perl
 can be made to issue a warning.)
 <br>
 <br>
-(e) If PCRE2_UNGREEDY is set, the greediness of the repetition quantifiers is
+(c) If PCRE2_UNGREEDY is set, the greediness of the repetition quantifiers is
 inverted, that is, by default they are not greedy, but if followed by a
 question mark they are.
 <br>
 <br>
-(f) PCRE2_ANCHORED can be used at matching time to force a pattern to be tried
+(d) PCRE2_ANCHORED can be used at matching time to force a pattern to be tried
 only at the first matching position in the subject string.
 <br>
 <br>
-(g) The PCRE2_NOTBOL, PCRE2_NOTEOL, PCRE2_NOTEMPTY and PCRE2_NOTEMPTY_ATSTART
+(e) The PCRE2_NOTBOL, PCRE2_NOTEOL, PCRE2_NOTEMPTY and PCRE2_NOTEMPTY_ATSTART
 options have no Perl equivalents.
 <br>
 <br>
-(h) The \R escape sequence can be restricted to match only CR, LF, or CRLF
+(f) The \R escape sequence can be restricted to match only CR, LF, or CRLF
 by the PCRE2_BSR_ANYCRLF option.
 <br>
 <br>
-(i) The callout facility is PCRE2-specific. Perl supports codeblocks and
+(g) The callout facility is PCRE2-specific. Perl supports codeblocks and
 variable interpolation, but not general hooks on every match.
 <br>
 <br>
-(j) The partial matching facility is PCRE2-specific.
+(h) The partial matching facility is PCRE2-specific.
 <br>
 <br>
-(k) The alternative matching function (<b>pcre2_dfa_match()</b> matches in a
+(i) The alternative matching function (<b>pcre2_dfa_match()</b> matches in a
 different way and is not Perl-compatible.
 <br>
 <br>
-(l) PCRE2 recognizes some special sequences such as (*CR) or (*NO_JIT) at
+(j) PCRE2 recognizes some special sequences such as (*CR) or (*NO_JIT) at
 the start of a pattern. These set overall options that cannot be changed within
 the pattern.
 <br>
 <br>
-(m) PCRE2 supports non-atomic positive lookaround assertions. This is an
+(k) PCRE2 supports non-atomic positive lookaround assertions. This is an
 extension to the lookaround facilities. The default, Perl-compatible
 lookarounds are atomic.
 </P>
@@ -252,7 +241,7 @@ Cambridge, England.
 REVISION
 </b><br>
 <P>
-Last updated: 03 February 2023
+Last updated: 11 August 2023
 <br>
 Copyright &copy; 1997-2023 University of Cambridge.
 <br>

doc/html/pcre2limits.html

@@ -47,7 +47,12 @@ and unset offsets.
 All values in repeating quantifiers must be less than 65536.
 </P>
 <P>
-The maximum length of a lookbehind assertion is 65535 characters.
+There are two different limits that apply to branches of lookbehind assertions. 
+If every branch in such an assertion matches a fixed number of characters,
+the maximum length of any branch is 65535 characters. If any branch matches a 
+variable number of characters, then the maximum matching length for every 
+branch is limited. The default limit is set at compile time, defaulting to 255, 
+but can be changed by the calling program.
 </P>
 <P>
 There is no limit to the number of parenthesized groups, but there can be no
@@ -91,9 +96,9 @@ Cambridge, England.
 REVISION
 </b><br>
 <P>
-Last updated: 26 July 2022
+Last updated: August 2023
 <br>
-Copyright &copy; 1997-2022 University of Cambridge.
+Copyright &copy; 1997-2023 University of Cambridge.
 <br>
 <p>
 Return to the <a href="index.html">PCRE2 index page</a>.

doc/html/pcre2pattern.html

@@ -2452,10 +2452,10 @@ If every top-level alternative matches a fixed length, for example
 <pre>
   (?&#60;=colour|color)
 </pre>
-there is no restriction on the lengths, which do not have to be the same, as
-this example demonstrates. This is the only kind of lookbehind supported by
-PCRE2 versions earlier than 10.43 and by the alternative matching function
-<b>pcre2_dfa_match()</b>.
+there is a limit of 65535 characters to the lengths, which do not have to be
+the same, as this example demonstrates. This is the only kind of lookbehind
+supported by PCRE2 versions earlier than 10.43 and by the alternative matching
+function <b>pcre2_dfa_match()</b>.
 </P>
 <P>
 In PCRE2 10.43 and later, <b>pcre2_match()</b> supports lookbehind assertions in
@@ -2464,9 +2464,9 @@ for example
 <pre>
   (?&#60;=colou?r)
 </pre>
-The maximum matching length for the whole lookbehind is limited to a value set
-by the calling program (default 255 characters). Unlimited repetition (for
-example \d*) is not supported. In some cases, the escape sequence \K
+The maximum matching length for any branch of the lookbehind is limited to a
+value set by the calling program (default 255 characters). Unlimited repetition
+(for example \d*) is not supported. In some cases, the escape sequence \K
 <a href="#resetmatchstart">(see above)</a>
 can be used instead of a lookbehind assertion at the start of a pattern to get
 round the length limit restriction.
@@ -3781,7 +3781,7 @@ Cambridge, England.
 </P>
 <br><a name="SEC32" href="#TOC1">REVISION</a><br>
 <P>
-Last updated: 09 August 2023
+Last updated: 11 August 2023
 <br>
 Copyright &copy; 1997-2023 University of Cambridge.
 <br>

doc/html/pcre2syntax.html

@@ -463,8 +463,10 @@ setting with a similar syntax.
 </pre>
 Each top-level branch of a lookbehind must have a limit for the number of
 characters it matches. If any branch can match a variable number of characters,
-the maximum for the entire lookbehind is limited. If every branch matches a
-fixed number of characters, there is no constraint.
+the maximum for each branch is limited to a value set by the caller of
+<b>pcre2_compile()</b> or defaulted. The default is set when PCRE2 is built
+(ultimate default 255). If every branch matches a fixed number of characters,
+the limit for each branch is 65535 characters.
 </P>
 <br><a name="SEC22" href="#TOC1">NON-ATOMIC LOOKAROUND ASSERTIONS</a><br>
 <P>
@@ -602,7 +604,7 @@ Cambridge, England.
 </P>
 <br><a name="SEC31" href="#TOC1">REVISION</a><br>
 <P>
-Last updated: 09 August 2023
+Last updated: 11 August 2023
 <br>
 Copyright &copy; 1997-2023 University of Cambridge.
 <br>

doc/html/pcre2test.html

@@ -696,11 +696,12 @@ heavily used in the test files.
       jitfast                   use JIT fast path
       jitverify                 verify JIT use
       locale=<name>             use this locale
-      max_pattern_length=<n>    set the maximum pattern length
+      max_pattern_length=<n>    set maximum pattern length
+      max_varlookbehind=<n>     set maximum variable lookbehind length
       memory                    show memory used
       newline=<type>            set newline type
       null_context              compile with a NULL context
-      null_pattern              pass pattern as NULL 
+      null_pattern              pass pattern as NULL
       parens_nest_limit=<n>     set maximum parentheses depth
       posix                     use the POSIX API
       posix_nosub               use the POSIX API with REG_NOSUB
@@ -848,6 +849,17 @@ If <b>hex</b> or <b>use_length</b> is used with the POSIX wrapper API (see
 below), the REG_PEND extension is used to pass the pattern's length.
 </P>
 <br><b>
+Specifying a maximum for variable lookbehinds
+</b><br>
+<P>
+Variable lookbehind assertions are supported only if, for each one, there is a
+maximum length (in characters) that it can match. There is a limit on this,
+whose default can be set at build time, with an ultimate default of 255. The 
+<b>max_varlookbehind</b> modifier uses the <b>pcre2_set_max_varlookbehind()</b>
+function to change the limit. Lookbehinds whose branches each match a fixed
+length are limited to 65535 characters per branch.
+</P>
+<br><b>
 Specifying wide characters in 16-bit and 32-bit modes
 </b><br>
 <P>
@@ -2181,7 +2193,7 @@ Cambridge, England.
 </P>
 <br><a name="SEC21" href="#TOC1">REVISION</a><br>
 <P>
-Last updated: 17 July 2023
+Last updated: 11 August 2023
 <br>
 Copyright &copy; 1997-2023 University of Cambridge.
 <br>