Fix \K issues in pcre2grep.

ChangeLog

@@ -100,6 +100,11 @@ code for -g that handles the case when \K in an assertion causes the match to
 end at the original start point. Also arranged for it to detect when \K causes
 the end of a match to be before its start.
 
+24. Similar to 23 above, strange things (including loops) could happen in 
+pcre2grep when \K was used in an assertion when --colour was used or in 
+multiline mode. The "end at original start point" bug is fixed, and if the end 
+point is found to be before the start point, they are swapped.
+
 
 Version 10.30 14-August-2017
 ----------------------------

RunGrepTest

@@ -630,6 +630,17 @@ echo "RC=$?" >>testtrygrep
 (cd $srcdir; $valgrind $vjs $pcre2grep -Mn -A2 'start[\s]+end' testdata/grepinputM) >>testtrygrep
 echo "RC=$?" >>testtrygrep
 
+echo "---------------------------- Test 125 -----------------------------" >>testtrygrep
+printf "abcd\n" >testNinputgrep
+$valgrind $vjs $pcre2grep --colour=always '(?<=\K.)' testNinputgrep >>testtrygrep
+echo "RC=$?" >>testtrygrep
+$valgrind $vjs $pcre2grep --colour=always '(?=.\K)' testNinputgrep >>testtrygrep
+echo "RC=$?" >>testtrygrep
+$valgrind $vjs $pcre2grep --colour=always '(?<=\K[ac])' testNinputgrep >>testtrygrep
+echo "RC=$?" >>testtrygrep
+$valgrind $vjs $pcre2grep --colour=always '(?=[ac]\K)' testNinputgrep >>testtrygrep
+echo "RC=$?" >>testtrygrep
+
 
 # Now compare the results.
 

src/pcre2grep.c

@@ -2764,11 +2764,38 @@ while (ptr < endptr)
       if ((multiline || do_colour) && !invert)
         {
         int plength;
+        PCRE2_SIZE endprevious;
+
+        /* The use of \K may make the end offset earlier than the start. In
+        this situation, swap them round. */
+
+        if (offsets[0] > offsets[1])
+          {
+          PCRE2_SIZE temp = offsets[0];
+          offsets[0] = offsets[1];
+          offsets[1] = temp;
+          }
+
         FWRITE_IGNORE(ptr, 1, offsets[0], stdout);
         print_match(ptr + offsets[0], offsets[1] - offsets[0]);
+
         for (;;)
           {
-          startoffset = offsets[1];  /* Advance after previous match. */
+          PCRE2_SIZE oldstartoffset = pcre2_get_startchar(match_data);
+
+          endprevious = offsets[1];
+          startoffset = endprevious;  /* Advance after previous match. */
+
+          /* If the pattern contained a lookbehind that included \K, it is
+          possible that the end of the match might be at or before the actual
+          starting offset we have just used. In this case, start one character
+          further on. */
+
+          if (startoffset <= oldstartoffset)
+            {
+            startoffset = oldstartoffset + 1;
+            if (utf) while ((ptr[startoffset] & 0xc0) == 0x80) startoffset++;
+            }
 
           /* If the current match ended past the end of the line (only possible
           in multiline mode), we must move on to the line in which it did end
@@ -2782,6 +2809,7 @@ while (ptr < endptr)
             filepos += (int)(linelength + endlinelength);
             linenumber++;
             startoffset -= (int)(linelength + endlinelength);
+            endprevious -= (int)(linelength + endlinelength);
             t = end_of_line(ptr, endptr, &endlinelength);
             linelength = t - ptr - endlinelength;
             length = (size_t)(endptr - ptr);
@@ -2797,7 +2825,18 @@ while (ptr < endptr)
           loop for any that may follow. */
 
           if (!match_patterns(ptr, length, options, startoffset, &mrc)) break;
-          FWRITE_IGNORE(ptr + startoffset, 1, offsets[0] - startoffset, stdout);
+
+          /* The use of \K may make the end offset earlier than the start. In
+          this situation, swap them round. */
+
+          if (offsets[0] > offsets[1])
+            {
+            PCRE2_SIZE temp = offsets[0];
+            offsets[0] = offsets[1];
+            offsets[1] = temp;
+            }
+
+          FWRITE_IGNORE(ptr + endprevious, 1, offsets[0] - endprevious, stdout);
           print_match(ptr + offsets[0], offsets[1] - offsets[0]);
           }
 
@@ -2805,8 +2844,8 @@ while (ptr < endptr)
         and its line-ending characters (if they matched the pattern), so there
         may be no more to print. */
 
-        plength = (int)((linelength + endlinelength) - startoffset);
-        if (plength > 0) FWRITE_IGNORE(ptr + startoffset, 1, plength, stdout);
+        plength = (int)((linelength + endlinelength) - endprevious);
+        if (plength > 0) FWRITE_IGNORE(ptr + endprevious, 1, plength, stdout);
         }
 
       /* Not colouring or multiline; no need to search for further matches. */

testdata/grepoutput

@@ -936,3 +936,12 @@ end
 16:start end in between start
 end
 RC=0
+---------------------------- Test 125 -----------------------------
+abcd
+RC=0
+abcd
+RC=0
+abcd
+RC=0
+abcd
+RC=0