Don't split CRLF in pcre2_substitute() when it's a valid newline sequence.

ChangeLog

@@ -296,6 +296,9 @@ not dereferencing it) while handling lookbehind assertions.
 87. Failure to get memory for the match data in regcomp() is now given as a 
 regcomp() error instead of waiting for regexec() to pick it up.
 
+88. In pcre2_substitute(), ensure that CRLF is not split when it is a valid 
+newline sequence.
+
 
 Version 10.20 30-June-2015
 --------------------------

doc/pcre2api.3

@@ -1,4 +1,4 @@
-.TH PCRE2API 3 "10 November 2015" "PCRE2 10.21"
+.TH PCRE2API 3 "13 November 2015" "PCRE2 10.21"
 .SH NAME
 PCRE2 - Perl-compatible regular expressions (revised API)
 .sp
@@ -2729,6 +2729,11 @@ simultaneous substitutions, as this \fBpcre2test\fP example shows:
 There is an additional option, PCRE2_SUBSTITUTE_GLOBAL, which causes the
 function to iterate over the subject string, replacing every matching
 substring. If this is not set, only the first matching substring is replaced.
+If any matched substring has zero length, after the substitution has happened,
+an attempt to find a non-empty match at the same position is performed. If this 
+is not successful, the current position is advanced by one character except 
+when CRLF is a valid newline sequence and the next two characters are CR, LF.
+In this case, the current position is advanced by two characters.
 .P
 A second additional option, PCRE2_SUBSTITUTE_EXTENDED, causes extra processing
 to be applied to the replacement string. Without this option, only the dollar
@@ -3087,6 +3092,6 @@ Cambridge, England.
 .rs
 .sp
 .nf
-Last updated: 10 November 2015
+Last updated: 13 November 2015
 Copyright (c) 1997-2015 University of Cambridge.
 .fi

doc/pcre2pattern.3

@@ -1,4 +1,4 @@
-.TH PCRE2PATTERN 3 "10 November 2015" "PCRE2 10.21"
+.TH PCRE2PATTERN 3 "13 November 2015" "PCRE2 10.21"
 .SH NAME
 PCRE2 - Perl-compatible regular expressions (revised API)
 .SH "PCRE2 REGULAR EXPRESSION DETAILS"
@@ -671,8 +671,8 @@ below.
 This particular group matches either the two-character sequence CR followed by
 LF, or one of the single characters LF (linefeed, U+000A), VT (vertical tab,
 U+000B), FF (form feed, U+000C), CR (carriage return, U+000D), or NEL (next
-line, U+0085). The two-character sequence is treated as a single unit that
-cannot be split.
+line, U+0085). Because this is an atomic group, the two-character sequence is
+treated as a single unit that cannot be split.
 .P
 In other modes, two additional characters whose codepoints are greater than 255
 are added: LS (line separator, U+2028) and PS (paragraph separator, U+2029).
@@ -1183,6 +1183,18 @@ patterns that are anchored in single line mode because all branches start with
 when the \fIstartoffset\fP argument of \fBpcre2_match()\fP is non-zero. The
 PCRE2_DOLLAR_ENDONLY option is ignored if PCRE2_MULTILINE is set.
 .P
+When the newline convention (see
+.\" HTML <a href="#newlines">
+.\" </a>
+"Newline conventions"
+.\"
+below) recognizes the two-character sequence CRLF as a newline, this is 
+preferred, even if the single characters CR and LF are also recognized as 
+newlines. For example, if the newline convention is "any", a multiline mode
+circumflex matches before "xyz" in the string "abc\er\enxyz" rather than after
+CR, even though CR on its own is a valid newline. (It also matches at the very 
+start of the string, of course.)
+.P
 Note that the sequences \eA, \eZ, and \ez can be used to match the start and
 end of the subject in both modes, and if all branches of a pattern start with
 \eA it is always anchored, whether or not PCRE2_MULTILINE is set.
@@ -3413,6 +3425,6 @@ Cambridge, England.
 .rs
 .sp
 .nf
-Last updated: 10 November 2015
+Last updated: 13 November 2015
 Copyright (c) 1997-2015 University of Cambridge.
 .fi

src/pcre2_substitute.c

@@ -296,8 +296,22 @@ do
     if (rc != PCRE2_ERROR_NOMATCH) goto EXIT;
     if (goptions == 0 || start_offset >= length) break;
 
+    /* Advance by one code point. Then, if CRLF is a valid newline sequence and
+    we have advanced into the middle of it, advance one more code point. In
+    other words, do not start in the middle of CRLF, even if CR and LF on their
+    own are valid newlines. */
+
     save_start = start_offset++;
-    if ((code->overall_options & PCRE2_UTF) != 0)
+    if (subject[start_offset-1] == CHAR_CR &&
+        code->newline_convention != PCRE2_NEWLINE_CR &&
+        code->newline_convention != PCRE2_NEWLINE_LF &&
+        start_offset < length &&
+        subject[start_offset] == CHAR_LF)
+      start_offset++;
+
+    /* Otherwise, in UTF mode, advance past any secondary code points. */
+
+    else if ((code->overall_options & PCRE2_UTF) != 0)
       {
 #if PCRE2_CODE_UNIT_WIDTH == 8
       while (start_offset < length && (subject[start_offset] & 0xc0) == 0x80)

testdata/testinput2

@@ -498,6 +498,9 @@
 /^ab\n/Igm,aftertext
     ab\nab\ncd
 
+/^/gm,newline=any
+    a\rb\nc\r\nxyz\=aftertext
+
 /abc/I
 
 /abc|bac/I
@@ -4659,4 +4662,18 @@ a)"xI
 
 /(?|(a)|())/BI
 
+# Test CRLF handling in empty string substitutions
+
+/^$/gm,newline=anycrlf,replace=-
+    X\r\n\r\nY
+
+/^$/gm,newline=crlf,replace=-
+    X\r\n\r\nY
+
+/^$/gm,newline=any,replace=-
+    X\r\n\r\nY
+
+"(*ANYCRLF)(?m)^(.*[^0-9\r\n].*|)$"g,replace=NaN
+    15\r\nfoo\r\n20\r\nbar\r\nbaz\r\n\r\n20
+
 # End of testinput2 

testdata/testoutput2

@@ -1316,6 +1316,17 @@ Subject length lower bound = 3
  0: ab\x0a
  0+ cd
 
+/^/gm,newline=any
+    a\rb\nc\r\nxyz\=aftertext
+ 0: 
+ 0+ a\x0db\x0ac\x0d\x0axyz
+ 0: 
+ 0+ b\x0ac\x0d\x0axyz
+ 0: 
+ 0+ c\x0d\x0axyz
+ 0: 
+ 0+ xyz
+
 /abc/I
 Capturing subpattern count = 0
 First code unit = 'a'
@@ -14842,4 +14853,22 @@ Capturing subpattern count = 1
 May match empty string
 Subject length lower bound = 0
 
+# Test CRLF handling in empty string substitutions
+
+/^$/gm,newline=anycrlf,replace=-
+    X\r\n\r\nY
+ 1: X\x0d\x0a-\x0d\x0aY
+
+/^$/gm,newline=crlf,replace=-
+    X\r\n\r\nY
+ 1: X\x0d\x0a-\x0d\x0aY
+
+/^$/gm,newline=any,replace=-
+    X\r\n\r\nY
+ 1: X\x0d\x0a-\x0d\x0aY
+
+"(*ANYCRLF)(?m)^(.*[^0-9\r\n].*|)$"g,replace=NaN
+    15\r\nfoo\r\n20\r\nbar\r\nbaz\r\n\r\n20
+ 4: 15\x0d\x0aNaN\x0d\x0a20\x0d\x0aNaN\x0d\x0aNaN\x0d\x0aNaN\x0d\x0a20
+
 # End of testinput2