Simple JNI examples for certain crashes

readme.txt

Steps to build on windows:
1. Compile java source

  javac JniEx.java

2. Make header file

  javah -jni JniEx

3. build dll

  build.bat

  # This needs to be run in visual studio express command prompt
  # since the batch file uses cl.exe and link.exe.

For linux, ran make (using Makefile) to build libJniEx.so.  The JNI include path is hardcoded in Makefile (see JNI_HDR_BASE line).  Change the line for your environment.

Linux output example:
1.5:
$ D_LIBRARY_PATH=$(pwd) ~/local/jdk1.5.0_17/bin/java JniEx alloc
 :
 23821 0x94fcfe8
 23822 0x0

Exception in thread "CompilerThread0" java.lang.OutOfMemoryError: requested 108776 bytes for Chunk::new. Out of swap space?

1.6:
$ LD_LIBRARY_PATH=$(pwd) ~/local/jdk1.6.0_26/bin/java JniEx alloc
 :
 24370 0xffffffffbffc4008
 24371 0xffffffffbffde008
 24372 0x0
#
# There is insufficient memory for the Java Runtime Environment to continue.
# Native memory allocation (malloc) failed to allocate 119248 bytes for Chunk::new
# An error report file with more information is saved as:
# /home/yoshi/lang/j/vm_exit_out_of_memory/hs_err_pid29135.log
Aborted (core dumped)

build.bat

rem change java_home as needed
set java_home=c:\Program Files (x86)\Java\jdk1.6.0_22
set java_include="%java_home%"\include

cl /c /I. /I%java_include% /I%java_include%\win32 JniEx.cpp

rem use /OUT:<filename> to change output filename
link /dll JniEx.obj

JniEx.cpp

#include "JniEx.h"
#include <stdlib.h>

void bad_func()
{
  int *ip = (int*)0xbffffffe;
  *ip = 1;
}

JNIEXPORT void JNICALL Java_JniEx_crash (JNIEnv *env, jclass cls) {
  bad_func();
}

JNIEXPORT jlong JNICALL Java_JniEx_malloc
  (JNIEnv *env, jclass cls, jint sz) {
  return (jlong)malloc(sz);
}

JniEx.java

import java.util.regex.*;
import javax.xml.parsers.*;
import org.xml.sax.InputSource;
import org.w3c.dom.*;
import java.io.*;

public class JniEx {
  static {
    System.loadLibrary("JniEx");
  }
  public static void usage() {
    String msg = "usage: java JniEx <crash|alloc>";
    System.out.println(msg);
  }

  public static void main(String[] args) {
    String op = "crash";
    if (args.length > 0) {
      if (args[0].equals("alloc")) {
        op = "alloc";
      }
    }
    if (op.equals("crash")) {
      System.out.println("calling crash...");
      crash();
    } else if (op.equals("alloc")) {
      System.out.println("allocating mem");
      int i = 0;
      while (true) {
        //long addr = malloc(1024*1024);
        long addr = malloc(1024*102);
        System.out.println(String.format("%6d %#x", i, addr));
        if (addr == 0) break;
        i++;
      }
      doSomething();
    } else {
      usage();
    }
  }
  public static native void crash();
  public static native long malloc(int size);
  static void doSomething() {
    doRegEx();
    doXML();
  }
  static void doRegEx() {
    String[] patterns = {"^java", "^javax", "^javax.swing", "javax\\.*"};
    String[] strings = {"java.lang.String", "javax.swing.JFrame",
                        "javax.xml.Node", "java.util.Vector"};
    for (int i = 0; i < 11000; i++) {
      for (String ps : patterns) {
        Pattern p = Pattern.compile(ps);
        for (String tx : strings) {
          Matcher m = p.matcher(tx);
          if (m.matches()) {
            incMCount();
          }
        }
      }
    }
  }
  public static long mcount = 0;
  public static void incMCount() { mcount++; }
  public static long getMCount() { return mcount; }
  static void doXML() {
    try {
      for (int i = 0; i < 11000; i++) {
        doXML0();
      }
    } catch (Exception e) { e.printStackTrace(); }
  }
  static void doXML0() throws Exception {
    DocumentBuilderFactory fac = DocumentBuilderFactory.newInstance();
    DocumentBuilder db = fac.newDocumentBuilder();
    StringReader sr = new StringReader("<books> <book><author>joe</author><title>foo</title></book> <book><author>joe2</author><title>foo2</title></book> <book><author>joe3</author><title>foo3</title></book> <book><author>joe4</author><title>foo4</title></book> <book><author>joe5</author><title>foo5</title></book> </books>");
    Document doc = db.parse(new InputSource(sr));
    walkNode(doc);
  }
  static void walkNode(Node n) {
    NodeList nl = n.getChildNodes();
    for (int i = 0; i < nl.getLength(); i++) {
      Node cn = nl.item(i);
      nvisited++;
      walkNode(cn);
    }
  }
  static long nvisited = 0L;
}

Makefile

SRC = JniEx.cpp
OLIB = libJniEx.so
all: $(OLIB)

JNI_HDR_BASE = /home/yoshi/local/jdk1.5.0_06/include
CXXFLAGS = -o $(OLIB) -shared -Wl,-soname,$(OLIB) -I$(JNI_HDR_BASE) -I$(JNI_HDR_BASE)/linux $(SRC) -static -lc 

$(OLIB): $(SRC)
	$(CXX) $(CXXFLAGS)