[GR-70603] Allow ProgressReporterUtils#truncateFQN(String, int) to truncate further

PullRequest: graal/22321

Author: olpaw

substratevm/src/com.oracle.svm.hosted/src/com/oracle/svm/hosted/ProgressReporterUtils.java

@@ -25,11 +25,11 @@
 
 package com.oracle.svm.hosted;
 
-import com.oracle.svm.core.util.ByteFormattingUtil;
-
 import java.net.URL;
 import java.security.CodeSource;
 
+import com.oracle.svm.core.util.ByteFormattingUtil;
+
 final class ProgressReporterUtils {
 
     private static final double MILLIS_TO_SECONDS = 1000d;
@@ -85,12 +85,22 @@ static String truncateFQN(String fqn, int maxLength) {
                 }
                 break;
             }
+            if (sb.length() + 2 >= maxLength) {
+                // if next char + '.' reaches limit, stop
+                sb.append(TRUNCATION_PLACEHOLDER);
+                break;
+            }
             sb.append(fqn.charAt(currentDot + 1)).append('.');
             if (sb.length() + (classNameLength - nextDot) <= maxLength) {
                 // Rest fits maxLength, append and return.
                 sb.append(fqn.substring(nextDot + 1));
                 break;
             }
+            if (sb.length() + 1 >= maxLength) {
+                // if no more space for next reduction, stop
+                sb.append(TRUNCATION_PLACEHOLDER);
+                break;
+            }
             currentDot = nextDot;
         }
         return sb.toString();