8311939: Excessive allocation of Matcher.groups array

Reviewed-by: rriggs, igraves

src/java.base/share/classes/java/util/regex/Matcher.java

@@ -247,8 +247,7 @@ public final class Matcher implements MatchResult {
         this.text = text;
 
         // Allocate state storage
-        int parentGroupCount = Math.max(parent.capturingGroupCount, 10);
-        groups = new int[parentGroupCount * 2];
+        groups = new int[parent.capturingGroupCount * 2];
         locals = new int[parent.localCount];
         localsPos = new IntHashSet[parent.localTCNCount];
 
@@ -422,8 +421,7 @@ public final class Matcher implements MatchResult {
         namedGroups = null;
 
         // Reallocate state storage
-        int parentGroupCount = Math.max(newPattern.capturingGroupCount, 10);
-        groups = new int[parentGroupCount * 2];
+        groups = new int[newPattern.capturingGroupCount * 2];
         locals = new int[newPattern.localCount];
         for (int i = 0; i < groups.length; i++)
             groups[i] = -1;

src/java.base/share/classes/java/util/regex/Pattern.java

@@ -5187,6 +5187,12 @@ loop:   for(int x=0, offset=0; x<nCodePoints; x++, offset+=len) {
             groupIndex = groupCount + groupCount;
         }
         boolean match(Matcher matcher, int i, CharSequence seq) {
+            // reference to not existing group must never match
+            // group does not exist if matcher didn't allocate space for it
+            if (groupIndex >= matcher.groups.length) {
+                return false;
+            }
+
             int j = matcher.groups[groupIndex];
             int k = matcher.groups[groupIndex+1];
 
@@ -5223,6 +5229,12 @@ loop:   for(int x=0, offset=0; x<nCodePoints; x++, offset+=len) {
             this.doUnicodeCase = doUnicodeCase;
         }
         boolean match(Matcher matcher, int i, CharSequence seq) {
+            // reference to not existing group must never match
+            // group does not exist if matcher didn't allocate space for it
+            if (groupIndex >= matcher.groups.length) {
+                return false;
+            }
+
             int j = matcher.groups[groupIndex];
             int k = matcher.groups[groupIndex+1];
 

test/jdk/java/util/regex/RegExTest.java

@@ -2041,6 +2041,58 @@ public class RegExTest {
         check(pattern, toSupplementaries("abcdefghijkk"), true);
     }
 
+    @Test
+    public static void ciBackRefTest() {
+        Pattern pattern = Pattern.compile("(?i)(a*)bc\\1");
+        check(pattern, "zzzaabcazzz", true);
+
+        pattern = Pattern.compile("(?i)(a*)bc\\1");
+        check(pattern, "zzzaabcaazzz", true);
+
+        pattern = Pattern.compile("(?i)(abc)(def)\\1");
+        check(pattern, "abcdefabc", true);
+
+        pattern = Pattern.compile("(?i)(abc)(def)\\3");
+        check(pattern, "abcdefabc", false);
+
+        for (int i = 1; i < 10; i++) {
+            // Make sure backref 1-9 are always accepted
+            pattern = Pattern.compile("(?i)abcdef\\" + i);
+            // and fail to match if the target group does not exit
+            check(pattern, "abcdef", false);
+        }
+
+        pattern = Pattern.compile("(?i)(a)(b)(c)(d)(e)(f)(g)(h)(i)(j)\\11");
+        check(pattern, "abcdefghija", false);
+        check(pattern, "abcdefghija1", true);
+
+        pattern = Pattern.compile("(?i)(a)(b)(c)(d)(e)(f)(g)(h)(i)(j)(k)\\11");
+        check(pattern, "abcdefghijkk", true);
+
+        pattern = Pattern.compile("(?i)(a)bcdefghij\\11");
+        check(pattern, "abcdefghija1", true);
+
+        // Supplementary character tests
+        pattern = Pattern.compile("(?i)" + toSupplementaries("(a*)bc\\1"));
+        check(pattern, toSupplementaries("zzzaabcazzz"), true);
+
+        pattern = Pattern.compile("(?i)" + toSupplementaries("(a*)bc\\1"));
+        check(pattern, toSupplementaries("zzzaabcaazzz"), true);
+
+        pattern = Pattern.compile("(?i)" + toSupplementaries("(abc)(def)\\1"));
+        check(pattern, toSupplementaries("abcdefabc"), true);
+
+        pattern = Pattern.compile("(?i)" + toSupplementaries("(abc)(def)\\3"));
+        check(pattern, toSupplementaries("abcdefabc"), false);
+
+        pattern = Pattern.compile("(?i)" + toSupplementaries("(a)(b)(c)(d)(e)(f)(g)(h)(i)(j)\\11"));
+        check(pattern, toSupplementaries("abcdefghija"), false);
+        check(pattern, toSupplementaries("abcdefghija1"), true);
+
+        pattern = Pattern.compile("(?i)" + toSupplementaries("(a)(b)(c)(d)(e)(f)(g)(h)(i)(j)(k)\\11"));
+        check(pattern, toSupplementaries("abcdefghijkk"), true);
+    }
+
     /**
      * Unicode Technical Report #18, section 2.6 End of Line
      * There is no empty line to be matched in the sequence \u000D\u000A