没有添加本机代码的Java致命错误SIGSEGV

Question

我从Java编译器收到一条我不明白的错误消息。我在OSX 10.6,10.9和Ubuntu 14.04上使用Java 6和7测试了我的代码。当我使用Eclipse调试器或解释器（使用-Xint选项）运行时，一切运行正常。否则，我收到以下消息：

Java 1.6：

Invalid memory access of location 0x8 rip=0x1024e9660

Java 1.7：

#
# A fatal error has been detected by the Java Runtime Environment:
#
#  SIGSEGV (0xb) at pc=0x000000010f7a8262, pid=20344, tid=18179
#
# JRE version: Java(TM) SE Runtime Environment (7.0_60-b19) (build 1.7.0_60-b19)
# Java VM: Java HotSpot(TM) 64-Bit Server VM (24.60-b09 mixed mode bsd-amd64 compressed oops)
# Problematic frame:
# V  [libjvm.dylib+0x3a8262]  PhaseIdealLoop::idom_no_update(Node*) const+0x12
#
# Failed to write core dump. Core dumps have been disabled. To enable core dumping, try "ulimit -c unlimited" before starting Java again
#
# If you would like to submit a bug report, please visit:
#   http://bugreport.sun.com/bugreport/crash.jsp
#

Java 7的错误输出更多（保存到文件中），但不幸的是我无法将其放在此帖的字符限制中。有时候我需要运行我的代码几次以便出现错误，但它似乎经常出现。

我的测试用例涉及以对数标度缓存一些计算。具体来说，给定log（X），log（Y），...，我有一个小类来计算log（X + Y + ...）。然后我将结果缓存在HashMap中。

奇怪的是，改变一些循环索引似乎会使问题消失。特别是，如果我更换

for (int z = 1; z < x+1; z++) {
    double logSummand = Math.log(z + x + y);
    toReturn.addLogSummand(logSummand);
}

同

for (int z = 0; z < x; z++) {
    double logSummand = Math.log(1 + z + x + y);
    toReturn.addLogSummand(logSummand);
}

然后我没有收到错误消息，程序运行正常。

我的最小例子如下：

import java.util.Arrays;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
public class TestLogSum {
    public static void main(String[] args) {

        for (int i = 0; i < 6; i++) {
            for (int n = 2; n < 30; n++) {
                for (int j = 1; j <= n; j++) {
                    for (int k = 1; k <= j; k++) {
                        System.out.println(computeSum(k, j));                       
                    }
                }
            }
        }
    }

    private static Map<List<Integer>, Double> cache = new HashMap<List<Integer>, Double>();
    public static double computeSum(int x, int y) {     
        List<Integer> key = Arrays.asList(new Integer[] {x, y});

        if (!cache.containsKey(key)) {

            // explicitly creating/updating a double[] array, instead of using the LogSumArray wrapper object, will prevent the error
            LogSumArray toReturn = new LogSumArray(x);

            // changing loop indices will prevent the error
            // in particular, for(z=0; z<x-1; z++), and then using z+1 in place of z, will not produce error
//          for (int z = 0; z < x; z++) {
//              double logSummand = Math.log(1 + z + x + y);
            for (int z = 1; z < x+1; z++) {
                double logSummand = Math.log(z + x + y);
                toReturn.addLogSummand(logSummand);
            }

            // returning the value here without cacheing it will prevent the segfault
            cache.put(key, toReturn.retrieveLogSum());
        }
        return cache.get(key);
    }

    /*
     * Given a bunch of logarithms log(X),log(Y),log(Z),...
     * This class is used to compute the log of the sum, log(X+Y+Z+...)
     */
    private static class LogSumArray {      
        private double[] logSummandArray;
        private int currSize;

        private double maxLogSummand;

        public LogSumArray(int maxEntries) {
            this.logSummandArray = new double[maxEntries];

            this.currSize = 0;
            this.maxLogSummand = Double.NEGATIVE_INFINITY;
        }

        public void addLogSummand(double logSummand) {
            logSummandArray[currSize] = logSummand;
            currSize++;
            // removing this line will prevent the error
            maxLogSummand = Math.max(maxLogSummand, logSummand);
        }

        public double retrieveLogSum() {
            if (maxLogSummand == Double.NEGATIVE_INFINITY) return Double.NEGATIVE_INFINITY;

            assert currSize <= logSummandArray.length;

            double factorSum = 0;
            for (int i = 0; i < currSize; i++) {
                factorSum += Math.exp(logSummandArray[i] - maxLogSummand);
            }

            return Math.log(factorSum) + maxLogSummand;
        }
    }
}

Answer 1

因此，在阅读评论后，似乎这是JVM中需要向Oracle报告的错误。所以，我已经向Oracle提交了一份错误报告。当我收到他们的回复时，我会发布更新。

感谢所有尝试过代码的人，并发现它在您的机器上也会中断。

如果有人有能力/倾向于弄清楚编译器中的代码导致了这个错误，那么听到它会很棒:)

更新：甲骨文的某个人昨天做出回应，他说他准备了修复bug，并要求将我的代码作为回归测试包括:)他没有解释问题是什么，除了说它是在HotSpot JIT中，他确实给我发了一个关于他所做的改变的链接，万一有人感兴趣：http://cr.openjdk.java.net/~kvn/8046516/webrev/