src/java.base/windows/classes/java/lang/ProcessImpl.java - master - niceSOFT/openjdk21

src/java.base/windows/classes/java/lang/ProcessImpl.java
723 строки29 KB
Martin Balao
8339180: Enhanced Building of Processes: Follow-on Issue
04 янв 2025, 23:09
04 янв 2025, 23:094bd350f
/*
 * Copyright (c) 1995, 2022, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.  Oracle designates this
 * particular file as subject to the "Classpath" exception as provided
 * by Oracle in the LICENSE file that accompanied this code.
 *
 * This code 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
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 * or visit www.oracle.com if you need additional information or have any
 * questions.
 */

package java.lang;

import java.io.BufferedInputStream;
import java.io.BufferedOutputStream;
import java.io.File;
import java.io.FileDescriptor;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.lang.ProcessBuilder.Redirect;
import java.security.AccessController;
import java.security.PrivilegedAction;
import java.util.ArrayList;
import java.util.Locale;
import java.util.concurrent.CompletableFuture;
import java.util.concurrent.TimeUnit;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

import jdk.internal.access.JavaIOFileDescriptorAccess;
import jdk.internal.access.SharedSecrets;
import jdk.internal.ref.CleanerFactory;
import jdk.internal.misc.Blocker;
import sun.security.action.GetPropertyAction;

/* This class is for the exclusive use of ProcessBuilder.start() to
 * create new processes.
 *
 * @author Martin Buchholz
 * @since   1.5
 */

final class ProcessImpl extends Process {
    private static final JavaIOFileDescriptorAccess fdAccess
        = SharedSecrets.getJavaIOFileDescriptorAccess();

    // Windows platforms support a forcible kill signal.
    static final boolean SUPPORTS_NORMAL_TERMINATION = false;

    /**
     * Open a file for writing. If {@code append} is {@code true} then the file
     * is opened for atomic append directly and a FileOutputStream constructed
     * with the resulting handle. This is because a FileOutputStream created
     * to append to a file does not open the file in a manner that guarantees
     * that writes by the child process will be atomic.
     */
    @SuppressWarnings("removal")
    private static FileOutputStream newFileOutputStream(File f, boolean append)
        throws IOException
    {
        if (append) {
            String path = f.getPath();
            SecurityManager sm = System.getSecurityManager();
            if (sm != null)
                sm.checkWrite(path);
            long handle = openForAtomicAppend(path);
            final FileDescriptor fd = new FileDescriptor();
            fdAccess.setHandle(fd, handle);
            return AccessController.doPrivileged(
                new PrivilegedAction<FileOutputStream>() {
                    public FileOutputStream run() {
                        return new FileOutputStream(fd);
                    }
                }
            );
        } else {
            return new FileOutputStream(f);
        }
    }

    // System-dependent portion of ProcessBuilder.start()
    static Process start(String cmdarray[],
                         java.util.Map<String,String> environment,
                         String dir,
                         ProcessBuilder.Redirect[] redirects,
                         boolean redirectErrorStream)
        throws IOException
    {
        String envblock = ProcessEnvironment.toEnvironmentBlock(environment);

        FileInputStream  f0 = null;
        FileOutputStream f1 = null;
        FileOutputStream f2 = null;

        try {
            boolean forceNullOutputStream = false;
            long[] stdHandles;
            if (redirects == null) {
                stdHandles = new long[] { -1L, -1L, -1L };
            } else {
                stdHandles = new long[3];

                if (redirects[0] == Redirect.PIPE) {
                    stdHandles[0] = -1L;
                } else if (redirects[0] == Redirect.INHERIT) {
                    stdHandles[0] = fdAccess.getHandle(FileDescriptor.in);
                } else if (redirects[0] instanceof ProcessBuilder.RedirectPipeImpl) {
                    stdHandles[0] = fdAccess.getHandle(((ProcessBuilder.RedirectPipeImpl) redirects[0]).getFd());
                } else {
                    f0 = new FileInputStream(redirects[0].file());
                    stdHandles[0] = fdAccess.getHandle(f0.getFD());
                }

                if (redirects[1] == Redirect.PIPE) {
                    stdHandles[1] = -1L;
                } else if (redirects[1] == Redirect.INHERIT) {
                    stdHandles[1] = fdAccess.getHandle(FileDescriptor.out);
                } else if (redirects[1] instanceof ProcessBuilder.RedirectPipeImpl) {
                    stdHandles[1] = fdAccess.getHandle(((ProcessBuilder.RedirectPipeImpl) redirects[1]).getFd());
                    // Force getInputStream to return a null stream,
                    // the handle is directly assigned to the next process.
                    forceNullOutputStream = true;
                } else {
                    f1 = newFileOutputStream(redirects[1].file(),
                                             redirects[1].append());
                    stdHandles[1] = fdAccess.getHandle(f1.getFD());
                }

                if (redirects[2] == Redirect.PIPE) {
                    stdHandles[2] = -1L;
                } else if (redirects[2] == Redirect.INHERIT) {
                    stdHandles[2] = fdAccess.getHandle(FileDescriptor.err);
                } else if (redirects[2] instanceof ProcessBuilder.RedirectPipeImpl) {
                    stdHandles[2] = fdAccess.getHandle(((ProcessBuilder.RedirectPipeImpl) redirects[2]).getFd());
                } else {
                    f2 = newFileOutputStream(redirects[2].file(),
                                             redirects[2].append());
                    stdHandles[2] = fdAccess.getHandle(f2.getFD());
                }
            }

            Process p = new ProcessImpl(cmdarray, envblock, dir,
                                   stdHandles, forceNullOutputStream, redirectErrorStream);
            if (redirects != null) {
                // Copy the handles's if they are to be redirected to another process
                if (stdHandles[0] >= 0
                        && redirects[0] instanceof ProcessBuilder.RedirectPipeImpl) {
                    fdAccess.setHandle(((ProcessBuilder.RedirectPipeImpl) redirects[0]).getFd(),
                            stdHandles[0]);
                }
                if (stdHandles[1] >= 0
                        && redirects[1] instanceof ProcessBuilder.RedirectPipeImpl) {
                    fdAccess.setHandle(((ProcessBuilder.RedirectPipeImpl) redirects[1]).getFd(),
                            stdHandles[1]);
                }
                if (stdHandles[2] >= 0
                        && redirects[2] instanceof ProcessBuilder.RedirectPipeImpl) {
                    fdAccess.setHandle(((ProcessBuilder.RedirectPipeImpl) redirects[2]).getFd(),
                            stdHandles[2]);
                }
            }
            return p;
        } finally {
            // In theory, close() can throw IOException
            // (although it is rather unlikely to happen here)
            try { if (f0 != null) f0.close(); }
            finally {
                try { if (f1 != null) f1.close(); }
                finally { if (f2 != null) f2.close(); }
            }
        }

    }

    private static class LazyPattern {
        // Escape-support version:
        //    "(\")((?:\\\\\\1|.)+?)\\1|([^\\s\"]+)";
        private static final Pattern PATTERN =
            Pattern.compile("[^\\s\"]+|\"[^\"]*\"");
    };

    /* Parses the command string parameter into the executable name and
     * program arguments.
     *
     * The command string is broken into tokens. The token separator is a space
     * or quota character. The space inside quotation is not a token separator.
     * There are no escape sequences.
     */
    private static String[] getTokensFromCommand(String command) {
        ArrayList<String> matchList = new ArrayList<>(8);
        Matcher regexMatcher = LazyPattern.PATTERN.matcher(command);
        while (regexMatcher.find())
            matchList.add(regexMatcher.group());
        return matchList.toArray(new String[matchList.size()]);
    }

    private static final int VERIFICATION_CMD_BAT = 0;
    private static final int VERIFICATION_WIN32 = 1;
    private static final int VERIFICATION_WIN32_SAFE = 2; // inside quotes not allowed
    private static final int VERIFICATION_LEGACY = 3;
    // See Command shell overview for documentation of special characters.
    // https://docs.microsoft.com/en-us/previous-versions/windows/it-pro/windows-xp/bb490954(v=technet.10)
    private static final String ESCAPE_VERIFICATION[] = {
        // We guarantee the only command file execution for implicit [cmd.exe] run.
        //    http://technet.microsoft.com/en-us/library/bb490954.aspx
        // All space characters require quoting are checked in needsEscaping().
        "\"<>&|^",
        "\"<>",
        "\"<>",
        ""
    };

    private static String createCommandLine(int verificationType,
                                     final String executablePath,
                                     final String cmd[])
    {
        StringBuilder cmdbuf = new StringBuilder(80);

        cmdbuf.append(executablePath);

        for (int i = 1; i < cmd.length; ++i) {
            cmdbuf.append(' ');
            String s = cmd[i];
            if (needsEscaping(verificationType, s)) {
                cmdbuf.append('"');

                if (verificationType == VERIFICATION_WIN32_SAFE) {
                    // Insert the argument, adding '\' to quote any interior quotes
                    int length = s.length();
                    for (int j = 0; j < length; j++) {
                        char c = s.charAt(j);
                        if (c == DOUBLEQUOTE) {
                            int count = countLeadingBackslash(verificationType, s, j);
                            while (count-- > 0) {
                                cmdbuf.append(BACKSLASH);   // double the number of backslashes
                            }
                            cmdbuf.append(BACKSLASH);       // backslash to quote the quote
                        }
                        cmdbuf.append(c);
                    }
                } else {
                    cmdbuf.append(s);
                }
                // The code protects the [java.exe] and console command line
                // parser, that interprets the [\"] combination as an escape
                // sequence for the ["] char.
                //     http://msdn.microsoft.com/en-us/library/17w5ykft.aspx
                //
                // If the argument is an FS path, doubling of the tail [\]
                // char is not a problem for non-console applications.
                //
                // The [\"] sequence is not an escape sequence for the [cmd.exe]
                // command line parser. The case of the [""] tail escape
                // sequence could not be realized due to the argument validation
                // procedure.
                if (verificationType == VERIFICATION_WIN32_SAFE ||
                    verificationType == VERIFICATION_LEGACY) {
                    int count = countLeadingBackslash(verificationType, s, s.length());
                    while (count-- > 0) {
                        cmdbuf.append(BACKSLASH);   // double the number of backslashes
                    }
                }
                cmdbuf.append('"');
            } else if (verificationType == VERIFICATION_WIN32_SAFE &&
                 (s.startsWith("\"") && s.endsWith("\"") && s.length() > 2)) {
                // Check that quoted argument does not escape the final quote
                cmdbuf.append(s);
                int count = countLeadingBackslash(verificationType, s, s.length() - 1);
                while (count-- > 0) {
                    cmdbuf.insert(cmdbuf.length() - 1, BACKSLASH);    // double the number of backslashes
                }
            } else {
                cmdbuf.append(s);
            }
        }
        return cmdbuf.toString();
    }

    /**
     * Return the argument without quotes (first and last) if quoted, otherwise the arg.
     * @param str a string
     * @return the string without quotes
     */
    private static String unQuote(String str) {
        if (!str.startsWith("\"") || !str.endsWith("\"") || str.length() < 2)
            return str;    // no beginning or ending quote, or too short not quoted

        // Strip leading and trailing quotes
        return str.substring(1, str.length() - 1);
    }

    private static boolean needsEscaping(int verificationType, String arg) {
        if (arg.isEmpty())
            return true;            // Empty string is to be quoted

        // Switch off MS heuristic for internal ["].
        // Please, use the explicit [cmd.exe] call
        // if you need the internal ["].
        //    Example: "cmd.exe", "/C", "Extended_MS_Syntax"

        // For [.exe] or [.com] file the unpaired/internal ["]
        // in the argument is not a problem.
        String unquotedArg = unQuote(arg);
        boolean argIsQuoted = !arg.equals(unquotedArg);
        boolean embeddedQuote = unquotedArg.indexOf(DOUBLEQUOTE) >= 0;

        switch (verificationType) {
            case VERIFICATION_CMD_BAT:
                if (embeddedQuote) {
                    throw new IllegalArgumentException("Argument has embedded quote, " +
                            "use the explicit CMD.EXE call.");
                }
                break;  // break determine whether to quote
            case VERIFICATION_WIN32_SAFE:
                if (argIsQuoted && embeddedQuote)  {
                    throw new IllegalArgumentException("Malformed argument has embedded quote: "
                            + unquotedArg);
                }
                break;
            default:
                break;
        }

        if (!argIsQuoted) {
            for (int i = 0; i < arg.length(); i++) {
                char ch = arg.charAt(i);
                if (Character.isLetterOrDigit(ch))
                    continue;   // skip over common characters
                // All space chars require quotes and other mode specific characters
                if (Character.isSpaceChar(ch) ||
                        Character.isWhitespace(ch) ||
                        ESCAPE_VERIFICATION[verificationType].indexOf(ch) >= 0) {
                    return true;
                }
            }
        }
        return false;
    }

    private static String getExecutablePath(String path)
        throws IOException
    {
        String name = unQuote(path);
        if (name.indexOf(DOUBLEQUOTE) >= 0) {
            throw new IllegalArgumentException("Executable name has embedded quote, " +
                    "split the arguments: " + name);
        }
        // Win32 CreateProcess requires path to be normalized
        File fileToRun = new File(name);

        // From the [CreateProcess] function documentation:
        //
        // "If the file name does not contain an extension, .exe is appended.
        // Therefore, if the file name extension is .com, this parameter
        // must include the .com extension. If the file name ends in
        // a period (.) with no extension, or if the file name contains a path,
        // .exe is not appended."
        //
        // "If the file name !does not contain a directory path!,
        // the system searches for the executable file in the following
        // sequence:..."
        //
        // In practice ANY non-existent path is extended by [.exe] extension
        // in the [CreateProcess] function with the only exception:
        // the path ends by (.)

        return fileToRun.getPath();
    }

    /**
     * An executable is any program that is an EXE or does not have an extension
     * and the Windows createProcess will be looking for .exe.
     * The comparison is case insensitive based on the name.
     * @param executablePath the executable file
     * @return true if the path ends in .exe or does not have an extension.
     */
    private boolean isExe(String executablePath) {
        File file = new File(executablePath);
        String upName = file.getName().toUpperCase(Locale.ROOT);
        return (upName.endsWith(".EXE") || upName.indexOf('.') < 0);
    }

    // Old version that can be bypassed
    private boolean isShellFile(String executablePath) {
        String upPath = executablePath.toUpperCase();
        return (upPath.endsWith(".CMD") || upPath.endsWith(".BAT"));
    }

    private String quoteString(String arg) {
        StringBuilder argbuf = new StringBuilder(arg.length() + 2);
        return argbuf.append('"').append(arg).append('"').toString();
    }

    // Count backslashes before start index of string.
    // .bat files don't include backslashes as part of the quote
    private static int countLeadingBackslash(int verificationType,
                                             CharSequence input, int start) {
        if (verificationType == VERIFICATION_CMD_BAT)
            return 0;
        int j;
        for (j = start - 1; j >= 0 && input.charAt(j) == BACKSLASH; j--) {
            // just scanning backwards
        }
        return (start - 1) - j;  // number of BACKSLASHES
    }

    private static final char DOUBLEQUOTE = '\"';
    private static final char BACKSLASH = '\\';

    private final long handle;
    private final ProcessHandle processHandle;
    private OutputStream stdin_stream;
    private InputStream stdout_stream;
    private InputStream stderr_stream;

    @SuppressWarnings("removal")
    private ProcessImpl(String cmd[],
                        final String envblock,
                        final String path,
                        final long[] stdHandles,
                        boolean forceNullOutputStream,
                        final boolean redirectErrorStream)
        throws IOException
    {
        String cmdstr;
        final SecurityManager security = System.getSecurityManager();
        final String value = GetPropertyAction.
                privilegedGetProperty("jdk.lang.Process.allowAmbiguousCommands",
                        (security == null ? "true" : "false"));
        final boolean allowAmbiguousCommands = !"false".equalsIgnoreCase(value);

        if (allowAmbiguousCommands && security == null) {
            // Legacy mode.

            // Normalize path if possible.
            String executablePath = new File(cmd[0]).getPath();

            // No worry about internal, unpaired ["], and redirection/piping.
            if (needsEscaping(VERIFICATION_LEGACY, executablePath) )
                executablePath = quoteString(executablePath);

            cmdstr = createCommandLine(
                //legacy mode doesn't worry about extended verification
                VERIFICATION_LEGACY,
                executablePath,
                cmd);
        } else {
            String executablePath;
            try {
                executablePath = getExecutablePath(cmd[0]);
            } catch (IllegalArgumentException e) {
                // Workaround for the calls like
                // Runtime.getRuntime().exec("\"C:\\Program Files\\foo\" bar")

                // No chance to avoid CMD/BAT injection, except to do the work
                // right from the beginning. Otherwise we have too many corner
                // cases from
                //    Runtime.getRuntime().exec(String[] cmd [, ...])
                // calls with internal ["] and escape sequences.

                // Restore original command line.
                StringBuilder join = new StringBuilder();
                // terminal space in command line is ok
                for (String s : cmd)
                    join.append(s).append(' ');

                // Parse the command line again.
                cmd = getTokensFromCommand(join.toString());
                executablePath = getExecutablePath(cmd[0]);

                // Check new executable name once more
                if (security != null)
                    security.checkExec(executablePath);
            }

            // Quotation protects from interpretation of the [path] argument as
            // start of longer path with spaces. Quotation has no influence to
            // [.exe] extension heuristic.
            boolean isShell = allowAmbiguousCommands ? isShellFile(executablePath)
                    : !isExe(executablePath);
            cmdstr = createCommandLine(
                    // We need the extended verification procedures
                    isShell ? VERIFICATION_CMD_BAT
                            : (allowAmbiguousCommands ? VERIFICATION_WIN32 : VERIFICATION_WIN32_SAFE),
                    quoteString(executablePath),
                    cmd);
        }

        handle = create(cmdstr, envblock, path,
                        stdHandles, redirectErrorStream);
        // Register a cleaning function to close the handle
        final long local_handle = handle;    // local to prevent capture of this
        CleanerFactory.cleaner().register(this, () -> closeHandle(local_handle));

        processHandle = ProcessHandleImpl.getInternal(getProcessId0(handle));

        java.security.AccessController.doPrivileged(
        new java.security.PrivilegedAction<Void>() {
        public Void run() {
            if (stdHandles[0] == -1L)
                stdin_stream = ProcessBuilder.NullOutputStream.INSTANCE;
            else {
                FileDescriptor stdin_fd = new FileDescriptor();
                fdAccess.setHandle(stdin_fd, stdHandles[0]);
                fdAccess.registerCleanup(stdin_fd);
                stdin_stream = new BufferedOutputStream(
                    new FileOutputStream(stdin_fd));
            }

            if (stdHandles[1] == -1L || forceNullOutputStream)
                stdout_stream = ProcessBuilder.NullInputStream.INSTANCE;
            else {
                FileDescriptor stdout_fd = new FileDescriptor();
                fdAccess.setHandle(stdout_fd, stdHandles[1]);
                fdAccess.registerCleanup(stdout_fd);
                stdout_stream = new BufferedInputStream(
                    new PipeInputStream(stdout_fd));
            }

            if (stdHandles[2] == -1L)
                stderr_stream = ProcessBuilder.NullInputStream.INSTANCE;
            else {
                FileDescriptor stderr_fd = new FileDescriptor();
                fdAccess.setHandle(stderr_fd, stdHandles[2]);
                fdAccess.registerCleanup(stderr_fd);
                stderr_stream = new PipeInputStream(stderr_fd);
            }

            return null; }});
    }

    public OutputStream getOutputStream() {
        return stdin_stream;
    }

    public InputStream getInputStream() {
        return stdout_stream;
    }

    public InputStream getErrorStream() {
        return stderr_stream;
    }

    private static final int STILL_ACTIVE = getStillActive();
    private static native int getStillActive();

    public int exitValue() {
        int exitCode = getExitCodeProcess(handle);
        if (exitCode == STILL_ACTIVE)
            throw new IllegalThreadStateException("process has not exited");
        return exitCode;
    }
    private static native int getExitCodeProcess(long handle);

    public int waitFor() throws InterruptedException {
        long comp = Blocker.begin();
        try {
            waitForInterruptibly(handle);
        } finally {
            Blocker.end(comp);
        }
        if (Thread.interrupted())
            throw new InterruptedException();
        return getExitCodeProcess(handle);
    }

    private static native void waitForInterruptibly(long handle);

    @Override
    public boolean waitFor(long timeout, TimeUnit unit)
        throws InterruptedException
    {
        long remainingNanos = unit.toNanos(timeout);    // throw NPE before other conditions
        if (getExitCodeProcess(handle) != STILL_ACTIVE) return true;
        if (timeout <= 0) return false;

        long deadline = System.nanoTime() + remainingNanos;
        do {
            // Round up to next millisecond
            long msTimeout = TimeUnit.NANOSECONDS.toMillis(remainingNanos + 999_999L);
            if (msTimeout < 0) {
                // if wraps around then wait a long while
                msTimeout = Integer.MAX_VALUE;
            }
            long comp = Blocker.begin();
            try {
                waitForTimeoutInterruptibly(handle, msTimeout);
            } finally {
                Blocker.end(comp);
            }
            if (Thread.interrupted())
                throw new InterruptedException();
            if (getExitCodeProcess(handle) != STILL_ACTIVE) {
                return true;
            }
            remainingNanos = deadline - System.nanoTime();
        } while (remainingNanos > 0);

        return (getExitCodeProcess(handle) != STILL_ACTIVE);
    }

    private static native void waitForTimeoutInterruptibly(
        long handle, long timeoutMillis);

    @Override
    public void destroy() {
        terminateProcess(handle);
    }

    @Override
    public CompletableFuture<Process> onExit() {
        return ProcessHandleImpl.completion(pid(), false)
                .handleAsync((exitStatus, unusedThrowable) -> this);
    }

    @Override
    public ProcessHandle toHandle() {
        @SuppressWarnings("removal")
        SecurityManager sm = System.getSecurityManager();
        if (sm != null) {
            sm.checkPermission(new RuntimePermission("manageProcess"));
        }
        return processHandle;
    }

    @Override
    public boolean supportsNormalTermination() {
        return ProcessImpl.SUPPORTS_NORMAL_TERMINATION;
    }

    @Override
    public Process destroyForcibly() {
        destroy();
        return this;
    }

    private static native void terminateProcess(long handle);

    @Override
    public long pid() {
        return processHandle.pid();
    }

    private static native int getProcessId0(long handle);

    @Override
    public boolean isAlive() {
        return isProcessAlive(handle);
    }

    private static native boolean isProcessAlive(long handle);

    /**
     * The {@code toString} method returns a string consisting of
     * the native process ID of the process and the exit value of the process.
     *
     * @return a string representation of the object.
     */
    @Override
    public String toString() {
        int exitCode = getExitCodeProcess(handle);
        return new StringBuilder("Process[pid=").append(pid())
                .append(", exitValue=").append(exitCode == STILL_ACTIVE ? "\"not exited\"" : exitCode)
                .append("]").toString();
    }

    /**
     * Create a process using the win32 function CreateProcess.
     * The method is synchronized due to MS kb315939 problem.
     * All native handles should restore the inherit flag at the end of call.
     *
     * @param cmdstr the Windows command line
     * @param envblock NUL-separated, double-NUL-terminated list of
     *        environment strings in VAR=VALUE form
     * @param dir the working directory of the process, or null if
     *        inheriting the current directory from the parent process
     * @param stdHandles array of windows HANDLEs.  Indexes 0, 1, and
     *        2 correspond to standard input, standard output and
     *        standard error, respectively.  On input, a value of -1
     *        means to create a pipe to connect child and parent
     *        processes.  On output, a value which is not -1 is the
     *        parent pipe handle corresponding to the pipe which has
     *        been created.  An element of this array is -1 on input
     *        if and only if it is <em>not</em> -1 on output.
     * @param redirectErrorStream redirectErrorStream attribute
     * @return the native subprocess HANDLE returned by CreateProcess
     */
    private static synchronized native long create(String cmdstr,
                                      String envblock,
                                      String dir,
                                      long[] stdHandles,
                                      boolean redirectErrorStream)
        throws IOException;

    /**
     * Opens a file for atomic append. The file is created if it doesn't
     * already exist.
     *
     * @param path the file to open or create
     * @return the native HANDLE
     */
    private static native long openForAtomicAppend(String path)
        throws IOException;

    private static native boolean closeHandle(long handle);
}