From a0002b6d4179847d18a7630b640ba6a7435fb53a Mon Sep 17 00:00:00 2001
From: Duy Tran <tranleduy1233@gmail.com>
Date: Fri, 24 May 2024 03:25:19 +0700
Subject: [PATCH] Check recursion limit in `VisitorLevelSpecification` (#991)

Check recursion limit in `VisitorLevelSpecification` instead of relying on Java's StackOverflowError.

The current implementation may not work, JVM may kill the process when StackOverflowError occurs.
```
  default IExpr acceptChecked(IVisitor visitor) {
    try {
      return accept(visitor);
    } catch (StackOverflowError soe) {
      RecursionLimitExceeded.throwIt(Integer.MAX_VALUE, this);
    }
    return F.NIL;
  }
```

Co-authored-by: Duy Tran <mail@duytran.com>
---
 .../core/visit/VisitorLevelSpecification.java         | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/symja_android_library/matheclipse-core/src/main/java/org/matheclipse/core/visit/VisitorLevelSpecification.java b/symja_android_library/matheclipse-core/src/main/java/org/matheclipse/core/visit/VisitorLevelSpecification.java
index 480b7b3b3f..6d569c36dd 100644
--- a/symja_android_library/matheclipse-core/src/main/java/org/matheclipse/core/visit/VisitorLevelSpecification.java
+++ b/symja_android_library/matheclipse-core/src/main/java/org/matheclipse/core/visit/VisitorLevelSpecification.java
@@ -1,7 +1,10 @@
 package org.matheclipse.core.visit;
 
 import java.util.function.Function;
+
+import org.matheclipse.core.basic.Config;
 import org.matheclipse.core.eval.EvalEngine;
+import org.matheclipse.core.eval.exception.RecursionLimitExceeded;
 import org.matheclipse.core.eval.exception.SymjaMathException;
 import org.matheclipse.core.expression.F;
 import org.matheclipse.core.interfaces.IASTMutable;
@@ -188,6 +191,7 @@ public IExpr visit(IAssociation assoc) {
       int[] minDepth = new int[] {0};
       try {
         fCurrentLevel++;
+        checkRecursionLimit(assoc);
         if (fIncludeHeads) {
           // no include head for associations
         }
@@ -228,6 +232,7 @@ public IExpr visit(IASTMutable ast) {
       int[] minDepth = new int[] {0};
       try {
         fCurrentLevel++;
+        checkRecursionLimit(ast);
         if (fIncludeHeads) {
           final IExpr temp = ast.get(0).accept(this);
           if (temp.isPresent()) {
@@ -270,6 +275,12 @@ public IExpr visit(IASTMutable ast) {
     return result[0];
   }
 
+  private void checkRecursionLimit(IExpr expr) {
+    if (this.fCurrentLevel > EvalEngine.get().getRecursionLimit()) {
+      RecursionLimitExceeded.throwIt(this.fCurrentLevel, expr);
+    }
+  }
+
   /**
    * Can be overridden in derived visitors.
    *