Forbid \K patterns that end before they start in pcre2_substitute().

ChangeLog

@@ -257,6 +257,9 @@ as /(?<=(a)(?-1))x/ which have a recursion within a backreference.
 
 74. Give an error if a lookbehind assertion is longer than 65535 code units.
 
+75. Give an error in pcre2_substitute() if a match ends before it starts (as a
+result of the use of \K).
+
 
 Version 10.20 30-June-2015
 --------------------------

doc/pcre2api.3

@@ -1,4 +1,4 @@
-.TH PCRE2API 3 "16 October 2015" "PCRE2 10.21"
+.TH PCRE2API 3 "03 November 2015" "PCRE2 10.21"
 .SH NAME
 PCRE2 - Perl-compatible regular expressions (revised API)
 .sp
@@ -2666,7 +2666,9 @@ same number causes an error at compile time.
 This function calls \fBpcre2_match()\fP and then makes a copy of the subject
 string in \fIoutputbuffer\fP, replacing the part that was matched with the
 \fIreplacement\fP string, whose length is supplied in \fBrlength\fP. This can
-be given as PCRE2_ZERO_TERMINATED for a zero-terminated string.
+be given as PCRE2_ZERO_TERMINATED for a zero-terminated string. Matches in 
+which a \eK item in a lookahead in the pattern causes the match to end before
+it starts are not supported, and give rise to an error return.
 .P
 The first seven arguments of \fBpcre2_substitute()\fP are the same as for
 \fBpcre2_match()\fP, except that the partial matching options are not
@@ -2769,8 +2771,9 @@ are passed straight back. PCRE2_ERROR_NOMEMORY is returned if the output buffer
 is not big enough. PCRE2_ERROR_BADREPLACEMENT is used for miscellaneous syntax
 errors in the replacement string, with more particular errors being
 PCRE2_ERROR_BADREPESCAPE (invalid escape sequence),
-PCRE2_ERROR_REPMISSING_BRACE (closing curly bracket not found), and
+PCRE2_ERROR_REPMISSING_BRACE (closing curly bracket not found),
-PCRE2_BADSUBSTITUTION (syntax error in extended group substitution). As for all
+PCRE2_BADSUBSTITUTION (syntax error in extended group substitution), and
+PCRE2_BADSUBPATTERN (the pattern match ended before it started). As for all
 PCRE2 errors, a text message that describes the error can be obtained by
 calling \fBpcre2_get_error_message()\fP.
 .
@@ -3066,6 +3069,6 @@ Cambridge, England.
 .rs
 .sp
 .nf
-Last updated: 16 October 2015
+Last updated: 03 November 2015
 Copyright (c) 1997-2015 University of Cambridge.
 .fi

src/pcre2.h

@@ -240,6 +240,7 @@ numbers must not be changed. */
 #define PCRE2_ERROR_BADREPESCAPE      (-57)
 #define PCRE2_ERROR_REPMISSINGBRACE   (-58)
 #define PCRE2_ERROR_BADSUBSTITUTION   (-59)
+#define PCRE2_ERROR_BADSUBSPATTERN    (-60)
 
 /* Request types for pcre2_pattern_info() */
 

src/pcre2.h.in

@@ -240,6 +240,7 @@ numbers must not be changed. */
 #define PCRE2_ERROR_BADREPESCAPE      (-57)
 #define PCRE2_ERROR_REPMISSINGBRACE   (-58)
 #define PCRE2_ERROR_BADSUBSTITUTION   (-59)
+#define PCRE2_ERROR_BADSUBSPATTERN    (-60)
 
 /* Request types for pcre2_pattern_info() */
 

src/pcre2_error.c

@@ -248,6 +248,8 @@ static const char match_error_texts[] =
   "bad escape sequence in replacement string\0"
   "expected closing curly bracket in replacement string\0"
   "bad substitution in replacement string\0"
+  /* 60 */
+  "match with end before start is not supported\0"
   ;
 
 

src/pcre2_substitute.c

@@ -320,7 +320,14 @@ do
     continue;
     }
 
-  /* Handle a successful match. */
+  /* Handle a successful match. Matches that use \K to end before they start
+  are not supported. */
+
+  if (ovector[1] < ovector[0])
+    {
+    rc = PCRE2_ERROR_BADSUBSPATTERN;
+    goto EXIT;
+    }
 
   subs++;
   if (rc == 0) rc = ovector_count;

testdata/testinput2

@@ -4596,4 +4596,7 @@ B)x/alt_verbnames,mark
 
 /(?<!a{65535})x/I
 
+/(?=a\K)/replace=z
+    BaCaD
+
 # End of testinput2 

testdata/testoutput2

@@ -14690,4 +14690,8 @@ Max lookbehind = 65535
 First code unit = 'x'
 Subject length lower bound = 1
 
+/(?=a\K)/replace=z
+    BaCaD
+Failed: error -60: match with end before start is not supported
+
 # End of testinput2