More partial match tweaks.

ChangeLog

@@ -104,7 +104,11 @@ within it, the nested lookbehind was not correctly processed. For example, if
     is another situation where adding characters to the current subject can
     lead to a full match. Example: /c*+(?<=[bc])/ with subject "ab".
     
-    (b) An empty string partial hard match can be returned for \z and \Z as it
+    (b) Similarly, if a pattern could match an empty string, an empty partial 
+    match may be given. Example: /(?![ab]).*/ with subject "ab". This case 
+    applies only to PCRE2_PARTIAL_HARD.
+    
+    (c) An empty string partial hard match can be returned for \z and \Z as it
     is documented that they shouldn't match. 
 
 

doc/html/pcre2api.html

@@ -2057,7 +2057,7 @@ the following negative numbers:
   PCRE2_ERROR_BADOPTION      the value of <i>what</i> was invalid
   PCRE2_ERROR_UNSET          the requested field is not set
 </pre>
-The "magic number" is placed at the start of each compiled pattern as an simple
+The "magic number" is placed at the start of each compiled pattern as a simple
 check against passing an arbitrary memory pointer. Here is a typical call of
 <b>pcre2_pattern_info()</b>, to obtain the length of the compiled pattern:
 <pre>
@@ -2114,7 +2114,7 @@ options returned for PCRE2_INFO_ALLOPTIONS.
   PCRE2_INFO_BACKREFMAX
 </pre>
 Return the number of the highest backreference in the pattern. The third
-argument should point to an <b>uint32_t</b> variable. Named capture groups
+argument should point to a <b>uint32_t</b> variable. Named capture groups
 acquire numbers as well as names, and these count towards the highest
 backreference. Backreferences such as \4 or \g{12} match the captured
 characters of the given group, but in addition, the check that a capture
@@ -2132,7 +2132,7 @@ that \R matches only CR, LF, or CRLF.
 </pre>
 Return the highest capture group number in the pattern. In patterns where (?|
 is not used, this is also the total number of capture groups. The third
-argument should point to an <b>uint32_t</b> variable.
+argument should point to a <b>uint32_t</b> variable.
 <pre>
   PCRE2_INFO_DEPTHLIMIT
 </pre>
@@ -2157,7 +2157,7 @@ returned. Otherwise NULL is returned. The third argument should point to a
   PCRE2_INFO_FIRSTCODETYPE
 </pre>
 Return information about the first code unit of any matched string, for a
-non-anchored pattern. The third argument should point to an <b>uint32_t</b>
+non-anchored pattern. The third argument should point to a <b>uint32_t</b>
 variable. If there is a fixed first value, for example, the letter "c" from a
 pattern such as (cat|cow|coyote), 1 is returned, and the value can be retrieved
 using PCRE2_INFO_FIRSTCODEUNIT. If there is no fixed first value, but it is
@@ -2169,7 +2169,7 @@ is returned.
 </pre>
 Return the value of the first code unit of any matched string for a pattern
 where PCRE2_INFO_FIRSTCODETYPE returns 1; otherwise return 0. The third
-argument should point to an <b>uint32_t</b> variable. In the 8-bit library, the
+argument should point to a <b>uint32_t</b> variable. In the 8-bit library, the
 value is always less than 256. In the 16-bit library the value can be up to
 0xffff. In the 32-bit library in UTF-32 mode the value can be up to 0x10ffff,
 and up to 0xffffffff when not using UTF-32 mode.
@@ -2185,12 +2185,12 @@ pattern. Each additional capture group adds two PCRE2_SIZE variables.
   PCRE2_INFO_HASBACKSLASHC
 </pre>
 Return 1 if the pattern contains any instances of \C, otherwise 0. The third
-argument should point to an <b>uint32_t</b> variable.
+argument should point to a <b>uint32_t</b> variable.
 <pre>
   PCRE2_INFO_HASCRORLF
 </pre>
 Return 1 if the pattern contains any explicit matches for CR or LF characters,
-otherwise 0. The third argument should point to an <b>uint32_t</b> variable. An
+otherwise 0. The third argument should point to a <b>uint32_t</b> variable. An
 explicit match is either a literal CR or LF character, or \r or \n or one of
 the equivalent hexadecimal or octal escape sequences.
 <pre>
@@ -2206,7 +2206,7 @@ defaulted by the caller of the match function.
   PCRE2_INFO_JCHANGED
 </pre>
 Return 1 if the (?J) or (?-J) option setting is used in the pattern, otherwise
-0. The third argument should point to an <b>uint32_t</b> variable. (?J) and
+0. The third argument should point to a <b>uint32_t</b> variable. (?J) and
 (?-J) set and unset the local PCRE2_DUPNAMES option, respectively.
 <pre>
   PCRE2_INFO_JITSIZE
@@ -2218,7 +2218,7 @@ return zero. The third argument should point to a <b>size_t</b> variable.
   PCRE2_INFO_LASTCODETYPE
 </pre>
 Returns 1 if there is a rightmost literal code unit that must exist in any
-matched string, other than at its start. The third argument should  point to an
+matched string, other than at its start. The third argument should  point to a
 <b>uint32_t</b> variable. If there is no such value, 0 is returned. When 1 is
 returned, the code unit value itself can be retrieved using
 PCRE2_INFO_LASTCODEUNIT. For anchored patterns, a last literal value is
@@ -2231,12 +2231,12 @@ PCRE2_INFO_LASTCODEUNIT), but for /^a\dz\d/ the returned value is 0.
 Return the value of the rightmost literal code unit that must exist in any
 matched string, other than at its start, for a pattern where
 PCRE2_INFO_LASTCODETYPE returns 1. Otherwise, return 0. The third argument
-should point to an <b>uint32_t</b> variable.
+should point to a <b>uint32_t</b> variable.
 <pre>
   PCRE2_INFO_MATCHEMPTY
 </pre>
 Return 1 if the pattern might match an empty string, otherwise 0. The third
-argument should point to an <b>uint32_t</b> variable. When a pattern contains
+argument should point to a <b>uint32_t</b> variable. When a pattern contains
 recursive subroutine calls it is not always possible to determine whether or
 not it can match an empty string. PCRE2 takes a cautious approach and returns 1
 in such cases.
@@ -2279,7 +2279,7 @@ If a minimum length for matching subject strings was computed, its value is
 returned. Otherwise the returned value is 0. This value is not computed when
 PCRE2_NO_START_OPTIMIZE is set. The value is a number of characters, which in
 UTF mode may be different from the number of code units. The third argument
-should point to an <b>uint32_t</b> variable. The value is a lower bound to the
+should point to a <b>uint32_t</b> variable. The value is a lower bound to the
 length of any matching string. There may not be any strings of that length that
 do actually match, but every string that does match is at least that long.
 <pre>
@@ -2726,7 +2726,8 @@ Your program may crash or loop indefinitely or give wrong results.
 These options turn on the partial matching feature. A partial match occurs if
 the end of the subject string is reached successfully, but there are not enough
 subject characters to complete the match. In addition, either at least one 
-character must have been inspected or the pattern must contain a lookbehind.
+character must have been inspected or the pattern must contain a lookbehind, or 
+the pattern must be one that could match an empty string.
 </P>
 <P>
 If this situation arises when PCRE2_PARTIAL_SOFT (but not PCRE2_PARTIAL_HARD)
@@ -3850,7 +3851,7 @@ Cambridge, England.
 </P>
 <br><a name="SEC42" href="#TOC1">REVISION</a><br>
 <P>
-Last updated: 20 July 2019
+Last updated: 22 July 2019
 <br>
 Copyright &copy; 1997-2019 University of Cambridge.
 <br>

doc/html/pcre2partial.html

@@ -80,16 +80,18 @@ is also disabled for partial matching.
 A partial match occurs during a call to <b>pcre2_match()</b> when the end of the
 subject string is reached successfully, but matching cannot continue because
 more characters are needed, and in addition, either at least one character in
-the subject has been inspected or the pattern contains a lookbehind. An
+the subject has been inspected or the pattern contains a lookbehind, or (when 
+PCRE2_PARTIAL_HARD is set) the pattern could match an empty string. An
 inspected character need not form part of the final matched string; lookbehind
 assertions and the \K escape sequence provide ways of inspecting characters
 before the start of a matched string.
 </P>
 <P>
-The two additional requirements define the cases where adding more characters
+The three additional requirements define the cases where adding more characters
-to the existing subject may complete the match. Without these conditions there
+to the existing subject may complete the same match that would occur if they
-would be a partial match of an empty string at the end of the subject for all 
+had all been present in the first place. Without these conditions there would
-unanchored patterns (and also for anchored patterns if the subject itself is 
+be a partial match of an empty string at the end of the subject for all
+unanchored patterns (and also for anchored patterns if the subject itself is
 empty).
 </P>
 <P>
@@ -449,7 +451,7 @@ Cambridge, England.
 </P>
 <br><a name="SEC10" href="#TOC1">REVISION</a><br>
 <P>
-Last updated: 21 July 2019
+Last updated: 22 July 2019
 <br>
 Copyright &copy; 1997-2019 University of Cambridge.
 <br>

doc/pcre2api.3

@@ -2720,7 +2720,8 @@ Your program may crash or loop indefinitely or give wrong results.
 These options turn on the partial matching feature. A partial match occurs if
 the end of the subject string is reached successfully, but there are not enough
 subject characters to complete the match. In addition, either at least one 
-character must have been inspected or the pattern must contain a lookbehind.
+character must have been inspected or the pattern must contain a lookbehind, or 
+the pattern must be one that could match an empty string.
 .P
 If this situation arises when PCRE2_PARTIAL_SOFT (but not PCRE2_PARTIAL_HARD)
 is set, matching continues by testing any remaining alternatives. Only if no

doc/pcre2partial.3

@@ -1,4 +1,4 @@
-.TH PCRE2PARTIAL 3 "21 July 2019" "PCRE2 10.34"
+.TH PCRE2PARTIAL 3 "22 July 2019" "PCRE2 10.34"
 .SH NAME
 PCRE2 - Perl-compatible regular expressions
 .SH "PARTIAL MATCHING IN PCRE2"
@@ -56,15 +56,17 @@ is also disabled for partial matching.
 A partial match occurs during a call to \fBpcre2_match()\fP when the end of the
 subject string is reached successfully, but matching cannot continue because
 more characters are needed, and in addition, either at least one character in
-the subject has been inspected or the pattern contains a lookbehind. An
+the subject has been inspected or the pattern contains a lookbehind, or (when 
+PCRE2_PARTIAL_HARD is set) the pattern could match an empty string. An
 inspected character need not form part of the final matched string; lookbehind
 assertions and the \eK escape sequence provide ways of inspecting characters
 before the start of a matched string.
 .P
-The two additional requirements define the cases where adding more characters
+The three additional requirements define the cases where adding more characters
-to the existing subject may complete the match. Without these conditions there
+to the existing subject may complete the same match that would occur if they
-would be a partial match of an empty string at the end of the subject for all 
+had all been present in the first place. Without these conditions there would
-unanchored patterns (and also for anchored patterns if the subject itself is 
+be a partial match of an empty string at the end of the subject for all
+unanchored patterns (and also for anchored patterns if the subject itself is
 empty).
 .P
 When a partial match is returned, the first two elements in the ovector point
@@ -422,6 +424,6 @@ Cambridge, England.
 .rs
 .sp
 .nf
-Last updated: 21 July 2019
+Last updated: 22 July 2019
 Copyright (c) 1997-2019 University of Cambridge.
 .fi

src/pcre2_dfa_match.c

@@ -3185,8 +3185,8 @@ for (;;)
           ptr >= end_subject &&              /* End of subject and */
             (                                  /* either */
             ptr > mb->start_used_ptr ||        /* Inspected non-empty string */
-            mb->haslookbehind                  /* or pattern has lookbehind */
+            mb->allowemptypartial              /* or pattern has lookbehind */
-            )
+            )                                  /* or could match empty */
           )
         ))
       match_count = PCRE2_ERROR_PARTIAL;
@@ -3417,7 +3417,8 @@ mb->tables = re->tables;
 mb->start_subject = subject;
 mb->end_subject = end_subject;
 mb->start_offset = start_offset;
-mb->haslookbehind = (re->max_lookbehind > 0);
+mb->allowemptypartial = (re->max_lookbehind > 0) ||
+  (re->flags & PCRE2_MATCH_EMPTY) != 0;
 mb->moptions = options;
 mb->poptions = re->overall_options;
 mb->match_call_count = 0;

src/pcre2_intmodedep.h

@@ -854,7 +854,7 @@ typedef struct match_block {
   uint32_t match_call_count;      /* Number of times a new frame is created */
   BOOL hitend;                    /* Hit the end of the subject at some point */
   BOOL hasthen;                   /* Pattern contains (*THEN) */
-  BOOL haslookbehind;             /* Pattern contains sigificant lookbehind */ 
+  BOOL allowemptypartial;         /* Allow empty hard partial */ 
   const uint8_t *lcc;             /* Points to lower casing table */
   const uint8_t *fcc;             /* Points to case-flipping table */
   const uint8_t *ctypes;          /* Points to table of type maps */
@@ -910,7 +910,7 @@ typedef struct dfa_match_block {
   uint32_t poptions;              /* Pattern options */
   uint32_t nltype;                /* Newline type */
   uint32_t nllen;                 /* Newline string length */
-  BOOL haslookbehind;             /* Pattern contains significant lookbehind */ 
+  BOOL allowemptypartial;         /* Allow empty hard partial */ 
   PCRE2_UCHAR nl[4];              /* Newline string when fixed */
   uint16_t bsr_convention;        /* \R interpretation */
   pcre2_callout_block *cb;        /* Points to a callout block */

src/pcre2_match.c

@@ -508,7 +508,8 @@ A partial match is returned only if no complete match can be found. */
     }
 
 #define SCHECK_PARTIAL()\
-  if (mb->partial != 0 && (Feptr > mb->start_used_ptr || mb->haslookbehind)) \
+  if (mb->partial != 0 && \
+      (Feptr > mb->start_used_ptr || mb->allowemptypartial)) \
     { \
     mb->hitend = TRUE; \
     if (mb->partial > 1) return PCRE2_ERROR_PARTIAL; \
@@ -6451,7 +6452,8 @@ mb->start_subject = subject;
 mb->start_offset = start_offset;
 mb->end_subject = end_subject;
 mb->hasthen = (re->flags & PCRE2_HASTHEN) != 0;
-mb->haslookbehind = (re->max_lookbehind > 0);
+mb->allowemptypartial = (re->max_lookbehind > 0) || 
+    (re->flags & PCRE2_MATCH_EMPTY) != 0;
 mb->poptions = re->overall_options;          /* Pattern options */
 mb->ignore_skip_arg = 0;
 mb->mark = mb->nomatch_mark = NULL;          /* In case never set */

testdata/testinput2

@@ -5719,4 +5719,10 @@ a)"xI
    abc\n\=ph,no_jit
    abc\n\=ps
 
+/(?![ab]).*/
+    ab\=ph,no_jit
+
+/c*+/
+    ab\=ph,offset=2,no_jit
+
 # End of testinput2

testdata/testinput6

@@ -5020,4 +5020,10 @@
     bxyz 
     xyz
 
+/(?![ab]).*/
+    ab\=ph
+
+/c*+/
+    ab\=ph,offset=2
+
 # End of testinput6

testdata/testoutput2

@@ -17231,6 +17231,14 @@ Partial match: \x0a
    abc\n\=ps
  0: 
 
+/(?![ab]).*/
+    ab\=ph,no_jit
+Partial match: 
+
+/c*+/
+    ab\=ph,offset=2,no_jit
+Partial match: 
+
 # End of testinput2
 Error -70: PCRE2_ERROR_BADDATA (unknown error number)
 Error -62: bad serialized data

testdata/testoutput6

@@ -7887,4 +7887,12 @@ Partial match:
     xyz
  0: 
 
+/(?![ab]).*/
+    ab\=ph
+Partial match: 
+
+/c*+/
+    ab\=ph,offset=2
+Partial match: 
+
 # End of testinput6