guard end-before-start match length in pcre2grep -o and --output

RunGrepTest

@@ -927,6 +927,17 @@ echo "RC=$?" >>testtrygrep
 (cd $srcdir; $valgrind $vjs $pcre2grep -n -B4 -A2 '^(ert|dfg)' ./testdata/grepinput) >>testtrygrep
 echo "RC=$?" >>testtrygrep
 
+echo "---------------------------- Test 161 -----------------------------" >>testtrygrep
+printf 'XfooY\n' >testNinputgrep
+$valgrind $vjs $pcre2grep --allow-lookaround-bsk -o '(?=foo\K)' testNinputgrep >>testtrygrep
+echo "RC=$?" >>testtrygrep
+$valgrind $vjs $pcre2grep --allow-lookaround-bsk --output '$0' '(?=foo\K)' testNinputgrep >>testtrygrep
+echo "RC=$?" >>testtrygrep
+$valgrind $vjs $pcre2grep --allow-lookaround-bsk --line-offsets '(?=foo\K)' testNinputgrep >>testtrygrep
+echo "RC=$?" >>testtrygrep
+$valgrind $vjs $pcre2grep --allow-lookaround-bsk --file-offsets '(?=foo\K)' testNinputgrep >>testtrygrep
+echo "RC=$?" >>testtrygrep
+
 
 # Now compare the results.
 

RunGrepTest.bat

@@ -897,6 +897,17 @@ echo RC=^%ERRORLEVEL%>>testtrygrep
 (pushd %srcdir% & %pcre2grep% -n -B4 -A2 "^(ert|dfg)" ./testdata/grepinput & popd) >>testtrygrep
 echo RC=^%ERRORLEVEL%>>testtrygrep
 
+echo ---------------------------- Test 161 ----------------------------->>testtrygrep
+%printf% "XfooY\n" >testNinputgrep
+%pcre2grep% --allow-lookaround-bsk -o "(?=foo\K)" testNinputgrep >>testtrygrep
+echo RC=^%ERRORLEVEL%>>testtrygrep
+%pcre2grep% --allow-lookaround-bsk --output "$0" "(?=foo\K)" testNinputgrep >>testtrygrep
+echo RC=^%ERRORLEVEL%>>testtrygrep
+%pcre2grep% --allow-lookaround-bsk --line-offsets "(?=foo\K)" testNinputgrep >>testtrygrep
+echo RC=^%ERRORLEVEL%>>testtrygrep
+%pcre2grep% --allow-lookaround-bsk --file-offsets "(?=foo\K)" testNinputgrep >>testtrygrep
+echo RC=^%ERRORLEVEL%>>testtrygrep
+
 :: Now compare the results.
 
 %cf% %srcdir%\testdata\grepoutput testtrygrep %cfout%

src/pcre2grep.c

@@ -2208,12 +2208,25 @@ for (; *string != 0; string++)
       case DDE_CAPTURE:
       if (value < capture_top)
         {
-        PCRE2_SIZE capturesize;
+        PCRE2_SIZE capturesize, start, end;
         value *= 2;
-        capturesize = ovector[value + 1] - ovector[value];
+        start = ovector[value];
+        end = ovector[value + 1];
+
+        /* The use of \K may make the end offset earlier than the start. In
+        this situation, swap them round. */
+
+        if (start > end)
+          {
+          PCRE2_SIZE temp = start;
+          start = end;
+          end = temp;
+          }
+
+        capturesize = end - start;
         if (capturesize > 0)
           {
-          print_match(subject + ovector[value], capturesize);
+          print_match(subject + start, capturesize);
           printed = TRUE;
           }
         }
@@ -2353,7 +2366,12 @@ while (length > 0)
       if (value < capture_top)
         {
         value *= 2;
-        argslen += ovector[value + 1] - ovector[value];
+
+        /* The use of \K may make the end offset earlier than the start. */
+
+        argslen += (ovector[value + 1] > ovector[value])?
+          ovector[value + 1] - ovector[value] :
+          ovector[value] - ovector[value + 1];
         }
       argslen--;   /* Negate the effect of argslen++ below. */
       break;
@@ -2419,10 +2437,23 @@ while (length > 0)
       case DDE_CAPTURE:
       if (value < capture_top)
         {
-        PCRE2_SIZE capturesize;
+        PCRE2_SIZE capturesize, start, end;
         value *= 2;
-        capturesize = ovector[value + 1] - ovector[value];
-        memcpy(argsptr, subject + ovector[value], capturesize);
+        start = ovector[value];
+        end = ovector[value + 1];
+
+        /* The use of \K may make the end offset earlier than the start. In
+        this situation, swap them round. */
+
+        if (start > end)
+          {
+          PCRE2_SIZE temp = start;
+          start = end;
+          end = temp;
+          }
+
+        capturesize = end - start;
+        memcpy(argsptr, subject + start, capturesize);
         argsptr += capturesize;
         }
       break;
@@ -2847,18 +2878,28 @@ while (ptr < endptr)
           printname_colon);
         if (number) fprintf(stdout, "%lu:", linenumber);
 
-        /* Handle --line-offsets */
+        /* Handle --line-offsets and --file-offsets. The use of \K may make
+        the end offset earlier than the start. In this situation, swap them
+        round. */
 
-        if (line_offsets)
-          fprintf(stdout, "%d,%d" STDOUT_NL, (int)(ptr + offsets[0] - ptr),
-            (int)(offsets[1] - offsets[0]));
+        if (line_offsets || file_offsets)
+          {
+          PCRE2_SIZE start = offsets[0];
+          PCRE2_SIZE end = offsets[1];
 
-        /* Handle --file-offsets */
+          if (start > end)
+            {
+            PCRE2_SIZE temp = start;
+            start = end;
+            end = temp;
+            }
 
-        else if (file_offsets)
-          fprintf(stdout, "%d,%d" STDOUT_NL,
-            (int)(filepos + ptr + offsets[0] - ptr),
-            (int)(offsets[1] - offsets[0]));
+          if (line_offsets)
+            fprintf(stdout, "%d,%d" STDOUT_NL, (int)start, (int)(end - start));
+          else
+            fprintf(stdout, "%d,%d" STDOUT_NL, (int)(filepos + start),
+              (int)(end - start));
+          }
 
         /* Handle --output (which has already been syntax checked) */
 
@@ -2881,12 +2922,26 @@ while (ptr < endptr)
             int n = om->groupnum;
             if (n == 0 || n < mrc)
               {
-              size_t plen = offsets[2*n + 1] - offsets[2*n];
+              PCRE2_SIZE start = offsets[2*n];
+              PCRE2_SIZE end = offsets[2*n + 1];
+              size_t plen;
+
+              /* The use of \K may make the end offset earlier than the start.
+              In this situation, swap them round. */
+
+              if (start > end)
+                {
+                PCRE2_SIZE temp = start;
+                start = end;
+                end = temp;
+                }
+
+              plen = end - start;
               if (plen > 0)
                 {
                 if (printed && om_separator != NULL)
                   fprintf(stdout, "%s", om_separator);
-                print_match(ptr + offsets[n*2], plen);
+                print_match(ptr + start, plen);
                 printed = TRUE;
                 }
               }

testdata/grepoutput

@@ -1339,3 +1339,12 @@ RC=0
 631-ghj
 632-jkl
 RC=0
+---------------------------- Test 161 -----------------------------
+foo
+RC=0
+foo
+RC=0
+1:1,3
+RC=0
+1,3
+RC=0