javapathfinder · aliiakbarkhan · Mar 10, 2026
diff --git a/README.md b/README.md
@@ -1 +1,248 @@
-jpf-nhandler============jpf-nhandler is an extension of Java PathFinder (JPF). It automatically delegates the execution of SUT methods from JPF to the host JVM. Execution of a call o.m(a) delegated by jpf-nhandler follows three main steps:  1. It transforms the JPF representation of o and a to the host JVM      level.  2. It delegates the execution to the original (non-native or native)      method m by invoking it on the host JVM.  3. Finally, it transforms the result of the method call back to its      JPF representation.The implementation of jpf-nhandler mostly relies on MJI. jpf-nhandler creates bytecode for native peers on-the-fly (they are called OTF peers from now on) using the BCEL library. To delegate the execution of a methodto the host JVM, jpf-nhandler adds a method in the corresponding OTF native peer which implements the three steps described above.The main applications of jpf-nhandler:  1. The key application of jpf-nhandler is to automatically intercept     and handle native calls within JPF. This extends the JPF functionality      considerably, since it allows JPF to verify numerous SUTs on which      JPF otherwise would crash.  2. By using jpf-nhandler, rather than model checking a call, the call      is executed outside of JPF, in its normal environment. Hence, this      tool can be used to reduce the state space and improve the scalability      of JPF.  3. JPF creates execution traces as it runs the SUT. Long traces can      cause JPF to run out of memory. In such cases, jpf-nhandler can be      used to delegate methods with long traces, and execute them on the      host JVM.  4. Delegating a method may also speed up JPF.jpf-nhandler can be configured in variety of ways. Here are some examples:  - It can be used to skip calls instead of delegating them. In this case     methods are executed as if they are empty and they just return some     dummy value.  - It also provides a way to specify which methods are delegated or skipped.    To force JPF to delegate the constructor of the class a.b.C, use        nhandler.spec.delegate = a.b.C.<init>    To force JPF to delegate all method in the String class, use        nhandler.spec.delegate = java.lang.String.*    To force JPF to skip java.io.FileDescriptor.write(), use        nhandler.spec.skip = java.io.FileDescriptor.write  - jpf-nhandler can also be configured to only delegate native calls which     are not handled in JPF  - jpf-nhandler can be also configured to generate source code for OTF     peers on-the-fly, which allows the user to subsequently refine its     implementation. Note that you can find bytecode and sources of    OTF peers in the following directory.        /jpf-nhandler/onthefly/    To generate sources, use        nhandler.genSource = true    If you refined and edited OTF sources and wish to compile them, run the     following command from jpf-nhandler.        javac -cp "<JPF_HOME>/build/jpf.jar:<NHANDLER_HOME>/build/jpf-nhandler.jar" <NHANDLER_HOME>/onthefly/*.java  - Since on-the-fly bytecode generation is expensive, one can also configure     jpf-nhandler to retain and reuse OTF peers for future runs, i.e. their     body may be extended as jpf-nhandler delegates more calls in the future.    To reuse sources, use        nhandler.clean = falseLimitations of jpf-nhandler---------------------------  1. The implementation of some classes is platform-specific, for instance      java.lang.System. jpf-nhandler cannot be used for such classes due to      inconsistencies between JPF and the host JVM.  2. Since jpf-nhandler relies on transforming objects and classes between      JPF and the host JVM, the state of a class or object should consist      of the same fields and superclasses in both the host JVM and JPF. This      limits the application of jpf-nhandler for types with JPF model classes      that are inconsistent with the actual class in the Java library.  3. The side effects of the delegated method should be only observable through      the return value, the arguments of the method, and the object or class     invoking the method, e.g. the lock() method in the class      java.util.concurrent.locks.ReentrantLock cannot be handled.  4. jpf-nhandler cannot handle certain objects of which part of their state      is kept natively, e.g. java.awt.WindowLicensing of jpf-nhandler-------------------------This extension is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version.This extension is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for more details.You can find a copy of the GNU General Public License athttp://www.gnu.org/licensesThe licenses of the jar files in lib/example have been included.  These jar filesare used in the examples.Installing of jpf-nhandler--------------------------To install jpf-nhandler, follow the steps below.1. Use [Java](https://www.oracle.com/ca-en/java/technologies/javase/javase8-archive-downloads.html)'s version 8 (we have successfully used 1.8.0_251, 1.8.0_281, and 1.8.0_301).  To check which version of Java (if any) is currently in use, issue the following command.```> java -versionjava version "1.8.0_251"Java(TM) SE Runtime Environment (build 1.8.0_251-b08)Java HotSpot(TM) 64-Bit Server VM (build 25.251-b08, mixed mode)```2. To check if any version of [Git](https://git-scm.com/downloads) is currently in use, issue the following command.```> git --versiongit version 2.26.2.windows.1```3. Install [jpf-core](https://github.com/javapathfinder/jpf-core) following the instructions on the [jpf-core wiki](https://github.com/javapathfinder/jpf-core/wiki/How-to-install-JPF). We recommend cloning the master branch using Git and building JPF with the Gradle wrapper. Note that some tests may fail. This should not prevent you from using JPF.4. Clone jpf-nhandler using Git: go the directory where you want to put jpf-nhandler and issue the following command.```> git clone https://github.com/javapathfinder/jpf-nhandler.gitCloning into 'jpf-nhandler'...remote: Enumerating objects: 1882, done.remote: Counting objects: 100% (1882/1882), done.remote: Compressing objects: 100% (581/581), done.remote: Total 1882 (delta 1122), reused 1882 (delta 1122), pack-reused 0Receiving objects: 100% (1882/1882), 6.84 MiB | 1.17 MiB/s, done.Resolving deltas: 100% (1122/1122), done.```5. Build jpf-nhandler with the Gradle wrapper: inside the jpf-nhandler directory, issue the following command.```> .\gradlew> Task :compileJavaC:\Users\montreal\Downloads\jpf\jpf-nhandler\src\main\java\nhandler\conversion\jpf2jvm\JPF2JVMGenericConverter.java:227: warning: sun.reflect.ReflectionFactory is internal proprietary API and may be removed in a future release        ctor = sun.reflect.ReflectionFactory.getReflectionFactory().newConstructorForSerialization(cl, Object.class.getConstructor());                          ^Note: Some input files use unchecked or unsafe operations.Note: Recompile with -Xlint:unchecked for details.1 warningBUILD SUCCESSFUL in 1s2 actionable tasks: 2 executed```6. Run jpf-nhandler's tests: issue the following command.```> .\gradlew test> Task :testconverter.JPF2JVMTest > convertClassTest PASSED...on_the_fly.StringTest > testIndexOf PASSEDTest Execution: SUCCESSSummary: 35 tests, 35 passed, 0 failed, 0 skippedBUILD SUCCESSFUL in 3s3 actionable tasks: 2 executed, 1 up-to-date```5. Add jpf-nhandler to the file site.properties.  See the [jpf-core wiki](https://github.com/javapathfinder/jpf-core/wiki/Creating-site-properties-file) for details.Running JPF with jpf-nhandler-----------------------------To run JPF on the class Example the *.jpf file includes    @using = jpf-nhandler    target = Example    nhandler.delegateUnhandledNative = true    classpath = path-to-application-classes    native_classpath = path-to-application-classesNote that to use jpf-nhandler, the classes used in the system under test should be specified both in classpath and native_classpath. Because the execution goes back and forth between JPF and the underlying host JVM, both JPF and the host JVM should be able to access these classes.Questions/comments/suggestions------------------------------Please email them to nastaran.shafiei@gmail.comThanks------to Peter Mehlitz for his help with the development of jpf-nhandler.
+jpf-nhandler
+============
+
+jpf-nhandler is an extension of Java PathFinder (JPF). It automatically 
+delegates the execution of SUT methods from JPF to the host JVM. Execution 
+of a call o.m(a) delegated by jpf-nhandler follows three main steps:
+
+  1. It transforms the JPF representation of o and a to the host JVM 
+     level.
+
+  2. It delegates the execution to the original (non-native or native) 
+     method m by invoking it on the host JVM.
+
+  3. Finally, it transforms the result of the method call back to its 
+     JPF representation.
+
+The implementation of jpf-nhandler mostly relies on MJI. jpf-nhandler 
+creates bytecode for native peers on-the-fly (they are called OTF peers 
+from now on) using the BCEL library. To delegate the execution of a method
+to the host JVM, jpf-nhandler adds a method in the corresponding OTF native 
+peer which implements the three steps described above.
+
+The main applications of jpf-nhandler:
+
+  1. The key application of jpf-nhandler is to automatically intercept
+     and handle native calls within JPF. This extends the JPF functionality 
+     considerably, since it allows JPF to verify numerous SUTs on which 
+     JPF otherwise would crash.
+
+  2. By using jpf-nhandler, rather than model checking a call, the call 
+     is executed outside of JPF, in its normal environment. Hence, this 
+     tool can be used to reduce the state space and improve the scalability 
+     of JPF.
+
+  3. JPF creates execution traces as it runs the SUT. Long traces can 
+     cause JPF to run out of memory. In such cases, jpf-nhandler can be 
+     used to delegate methods with long traces, and execute them on the 
+     host JVM.
+
+  4. Delegating a method may also speed up JPF.
+
+jpf-nhandler can be configured in variety of ways. Here are some examples:
+
+  - It can be used to skip calls instead of delegating them. In this case 
+    methods are executed as if they are empty and they just return some 
+    dummy value.
+
+  - It also provides a way to specify which methods are delegated or skipped.
+    To force JPF to delegate the constructor of the class a.b.C, use
+
+        nhandler.spec.delegate = a.b.C.<init>
+
+    To force JPF to delegate all method in the String class, use
+
+        nhandler.spec.delegate = java.lang.String.*
+
+    To force JPF to skip java.io.FileDescriptor.write(), use
+
+        nhandler.spec.skip = java.io.FileDescriptor.write
+
+  - jpf-nhandler can also be configured to only delegate native calls which 
+    are not handled in JPF
+
+  - jpf-nhandler can be also configured to generate source code for OTF 
+    peers on-the-fly, which allows the user to subsequently refine its 
+    implementation. Note that you can find bytecode and sources of
+    OTF peers in the following directory.
+
+        /jpf-nhandler/onthefly/
+
+    To generate sources, use
+
+        nhandler.genSource = true
+
+    If you refined and edited OTF sources and wish to compile them, run the 
+    following command from jpf-nhandler (use `:` as path separator on 
+    Linux/macOS and `;` on Windows).
+
+        javac -cp "<JPF_HOME>/build/jpf.jar:<NHANDLER_HOME>/build/jpf-nhandler.jar" <NHANDLER_HOME>/onthefly/*.java
+
+  - Since on-the-fly bytecode generation is expensive, one can also configure 
+    jpf-nhandler to retain and reuse OTF peers for future runs, i.e. their 
+    body may be extended as jpf-nhandler delegates more calls in the future.
+
+    To reuse sources, use
+
+        nhandler.clean = false
+
+Limitations of jpf-nhandler
+---------------------------
+
+  1. The implementation of some classes is platform-specific, for instance 
+     java.lang.System. jpf-nhandler cannot be used for such classes due to 
+     inconsistencies between JPF and the host JVM.
+
+  2. Since jpf-nhandler relies on transforming objects and classes between 
+     JPF and the host JVM, the state of a class or object should consist 
+     of the same fields and superclasses in both the host JVM and JPF. This 
+     limits the application of jpf-nhandler for types with JPF model classes 
+     that are inconsistent with the actual class in the Java library.
+
+  3. The side effects of the delegated method should be only observable through 
+     the return value, the arguments of the method, and the object or class
+     invoking the method, e.g. the lock() method in the class 
+     java.util.concurrent.locks.ReentrantLock cannot be handled.
+
+  4. jpf-nhandler cannot handle certain objects of which part of their state 
+     is kept natively, e.g. java.awt.Window
+
+
+Licensing of jpf-nhandler
+-------------------------
+
+This extension is free software: you can redistribute it and/or modify it 
+under the terms of the GNU General Public License as published by the Free 
+Software Foundation, either version 3 of the License, or (at your option) 
+any later version.
+
+This extension is distributed in the hope that it will be useful, but WITHOUT 
+ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS 
+FOR A PARTICULAR PURPOSE.  See the GNU General Public License for more details.
+
+You can find a copy of the GNU General Public License at
+http://www.gnu.org/licenses
+
+The licenses of the jar files in lib/example have been included.  These jar files
+are used in the examples.
+
+Installing of jpf-nhandler
+--------------------------
+
+To install jpf-nhandler, follow the steps below.
+
+1. Use [Java](https://www.oracle.com/java/technologies/javase/jdk11-archive-downloads.html)'s version 11 (we have successfully used 11.0.x releases).  To check which version of Java (if any) is currently in use, issue the following command.
+```
+> java -version
+java version "11.0.15" 2022-04-19 LTS
+Java(TM) SE Runtime Environment 18.9 (build 11.0.15+8-LTS-149)
+Java HotSpot(TM) 64-Bit Server VM 18.9 (build 11.0.15+8-LTS-149, mixed mode)
+```
+
+2. To check if any version of [Git](https://git-scm.com/downloads) is currently in use, issue the following command.
+```
+> git --version
+git version 2.26.2.windows.1
+```
+
+3. Install [jpf-core](https://github.com/javapathfinder/jpf-core) following the instructions on the [jpf-core wiki](https://github.com/javapathfinder/jpf-core/wiki/How-to-install-JPF). We recommend cloning the master branch using Git and building JPF with the Gradle wrapper. Make sure you use the Java 11 compatible branch/version of jpf-core. Note that some tests may fail. This should not prevent you from using JPF.
+
+4. Clone jpf-nhandler using Git: go the directory where you want to put jpf-nhandler and issue the following command.
+```
+> git clone https://github.com/javapathfinder/jpf-nhandler.git
+Cloning into 'jpf-nhandler'...
+remote: Enumerating objects: 1882, done.
+remote: Counting objects: 100% (1882/1882), done.
+remote: Compressing objects: 100% (581/581), done.
+remote: Total 1882 (delta 1122), reused 1882 (delta 1122), pack-reused 0
+Receiving objects: 100% (1882/1882), 6.84 MiB | 1.17 MiB/s, done.
+Resolving deltas: 100% (1122/1122), done.
+```
+
+5. Source file placement: jpf-nhandler uses the standard Gradle project layout. Place your files in the correct directory so that compilation and testing succeed.
+
+   - **Main sources** (the jpf-nhandler library itself) live under:
+
+         src/main/java/
+
+     For example, the core nhandler package is at `src/main/java/nhandler/` and
+     the MJI model classes (gov.nasa.jpf.*) are at `src/main/java/gov/`.
+     Example programs used to demonstrate jpf-nhandler are placed under
+     `src/main/java/example/` — these are excluded from the compiled jar but
+     are available on the classpath during tests.
+
+   - **Test sources** live under:
+
+         src/test/java/
+
+     JUnit 5 test classes go here (e.g. `src/test/java/converter/` and
+     `src/test/java/on_the_fly/`). Gradle picks them up automatically when
+     you run `.\gradlew test`.
+
+   If you add new source files outside these two directories, Gradle will not
+   compile or test them unless you update `sourceSets` in `build.gradle`.
+
+6. Build jpf-nhandler with the Gradle wrapper: inside the jpf-nhandler directory, issue the following command.
+```
+> .\gradlew
+
+> Task :compileJava
+Note: Some input files use unchecked or unsafe operations.
+Note: Recompile with -Xlint:unchecked for details.
+
+BUILD SUCCESSFUL in 1s
+2 actionable tasks: 2 executed
+```
+
+7. Run jpf-nhandler's tests: issue the following command.
+```
+> .\gradlew test
+
+> Task :test
+
+converter.JPF2JVMTest > convertClassTest PASSED
+
+...
+
+on_the_fly.StringTest > testIndexOf PASSED
+Test Execution: SUCCESS
+Summary: 35 tests, 35 passed, 0 failed, 0 skipped
+
+BUILD SUCCESSFUL in 3s
+3 actionable tasks: 2 executed, 1 up-to-date
+```
+
+8. Add jpf-nhandler to the file site.properties.  See the [jpf-core wiki](https://github.com/javapathfinder/jpf-core/wiki/Creating-site-properties-file) for details.
+
+
+Running JPF with jpf-nhandler
+-----------------------------
+
+To run JPF on the class Example the *.jpf file includes
+
+    @using = jpf-nhandler
+
+    target = Example
+
+    nhandler.delegateUnhandledNative = true
+
+    classpath = path-to-application-classes
+
+    native_classpath = path-to-application-classes
+
+Note that to use jpf-nhandler, the classes used in the system under test 
+should be specified both in classpath and native_classpath. Because the 
+execution goes back and forth between JPF and the underlying host JVM, 
+both JPF and the host JVM should be able to access these classes.
+
+
+Questions/comments/suggestions
+------------------------------
+
+Please email them to nastaran.shafiei@gmail.com
+
+
+Thanks
+------
+
+to Peter Mehlitz for his help with the development of jpf-nhandler.