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Java example source code file (java_md_macosx.c)

This example Java source code file (java_md_macosx.c) is included in the alvinalexander.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

Learn more about this Java project at its project page.

Java - Java tags/keywords

getarch, getjrepath, invocationfunctions, javavm, jli_getjavavminstance, jli_reporterrormessage, jli_snprintf, jli_strcmp, jli_tracelauncher, jni_false, jni_true, jnicall, jniexport, null

The java_md_macosx.c Java example source code

/*
 * Copyright (c) 2012, 2013, 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.
 */

#include "java.h"
#include "jvm_md.h"
#include <dirent.h>
#include <dlfcn.h>
#include <fcntl.h>
#include <inttypes.h>
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <sys/stat.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/time.h>

#include "manifest_info.h"
#include "version_comp.h"

/* Support Cocoa event loop on the main thread */
#include <Cocoa/Cocoa.h>
#include <objc/objc-runtime.h>
#include <objc/objc-auto.h>

#include <errno.h>
#include <spawn.h>

struct NSAppArgs {
    int argc;
    char **argv;
};

#define JVM_DLL "libjvm.dylib"
#define JAVA_DLL "libjava.dylib"
/* FALLBACK avoids naming conflicts with system libraries
 * (eg, ImageIO's libJPEG.dylib) */
#define LD_LIBRARY_PATH "DYLD_FALLBACK_LIBRARY_PATH"

/*
 * If a processor / os combination has the ability to run binaries of
 * two data models and cohabitation of jre/jdk bits with both data
 * models is supported, then DUAL_MODE is defined. MacOSX is a hybrid
 * system in that, the universal library can contain all types of libraries
 * 32/64 and client/server, thus the spawn is capable of linking with the
 * appropriate library as requested.
 *
 * Notes:
 * 1. VM. DUAL_MODE is disabled, and not supported, however, it is left here in
 *    for experimentation and perhaps enable it in the future.
 * 2. At the time of this writing, the universal library contains only
 *    a server 64-bit server JVM.
 * 3. "-client" command line option is supported merely as a command line flag,
 *    for, compatibility reasons, however, a server VM will be launched.
 */

/*
 * Flowchart of launcher execs and options processing on unix
 *
 * The selection of the proper vm shared library to open depends on
 * several classes of command line options, including vm "flavor"
 * options (-client, -server) and the data model options, -d32  and
 * -d64, as well as a version specification which may have come from
 * the command line or from the manifest of an executable jar file.
 * The vm selection options are not passed to the running
 * virtual machine; they must be screened out by the launcher.
 *
 * The version specification (if any) is processed first by the
 * platform independent routine SelectVersion.  This may result in
 * the exec of the specified launcher version.
 *
 * Now, in most cases,the launcher will dlopen the target libjvm.so. All
 * required libraries are loaded by the runtime linker, using the known paths
 * baked into the shared libraries at compile time. Therefore,
 * in most cases, the launcher will only exec, if the data models are
 * mismatched, and will not set any environment variables, regardless of the
 * data models.
 *
 *
 *
 *  Main
 *  (incoming argv)
 *  |
 * \|/
 * SelectVersion
 * (selects the JRE version, note: not data model)
 *  |
 * \|/
 * CreateExecutionEnvironment
 * (determines desired data model)
 *  |
 *  |
 * \|/
 *  Have Desired Model ? --> NO --> Is Dual-Mode ? --> NO --> Exit(with error)
 *  |                                          |
 *  |                                          |
 *  |                                         \|/
 *  |                                         YES
 *  |                                          |
 *  |                                          |
 *  |                                         \|/
 *  |                                CheckJvmType
 *  |                               (removes -client, -server etc.)
 *  |                                          |
 *  |                                          |
 * \|/                                        \|/
 * YES                             Find the desired executable/library
 *  |                                          |
 *  |                                          |
 * \|/                                        \|/
 * CheckJvmType                             POINT A
 * (removes -client, -server, etc.)
 *  |
 *  |
 * \|/
 * TranslateDashJArgs...
 * (Prepare to pass args to vm)
 *  |
 *  |
 * \|/
 * ParseArguments
 * (removes -d32 and -d64 if any,
 *  processes version options,
 *  creates argument list for vm,
 *  etc.)
 *   |
 *   |
 *  \|/
 * POINT A
 *   |
 *   |
 *  \|/
 * Path is desired JRE ? YES --> Have Desired Model ? NO --> Re-exec --> Main
 *  NO                               YES --> Continue
 *   |
 *   |
 *  \|/
 * Paths have well known
 * jvm paths ?       --> NO --> Have Desired Model ? NO --> Re-exec --> Main
 *  YES                              YES --> Continue
 *   |
 *   |
 *  \|/
 *  Does libjvm.so exist
 *  in any of them ? --> NO --> Have Desired Model ? NO --> Re-exec --> Main
 *   YES                             YES --> Continue
 *   |
 *   |
 *  \|/
 * Re-exec / Spawn
 *   |
 *   |
 *  \|/
 * Main
 */

#define GetArch() GetArchPath(CURRENT_DATA_MODEL)

/* Store the name of the executable once computed */
static char *execname = NULL;

/*
 * execname accessor from other parts of platform dependent logic
 */
const char *
GetExecName() {
    return execname;
}

const char *
GetArchPath(int nbits)
{
    switch(nbits) {
        default:
            return LIBARCHNAME;
    }
}


/*
 * Exports the JNI interface from libjli
 *
 * This allows client code to link against the .jre/.jdk bundles,
 * and not worry about trying to pick a HotSpot to link against.
 *
 * Switching architectures is unsupported, since client code has
 * made that choice before the JVM was requested.
 */

static InvocationFunctions *sExportedJNIFunctions = NULL;
static char *sPreferredJVMType = NULL;

static InvocationFunctions *GetExportedJNIFunctions() {
    if (sExportedJNIFunctions != NULL) return sExportedJNIFunctions;

    char jrePath[PATH_MAX];
    jboolean gotJREPath = GetJREPath(jrePath, sizeof(jrePath), GetArch(), JNI_FALSE);
    if (!gotJREPath) {
        JLI_ReportErrorMessage("Failed to GetJREPath()");
        return NULL;
    }

    char *preferredJVM = sPreferredJVMType;
    if (preferredJVM == NULL) {
#if defined(__i386__)
        preferredJVM = "client";
#elif defined(__x86_64__)
        preferredJVM = "server";
#else
#error "Unknown architecture - needs definition"
#endif
    }

    char jvmPath[PATH_MAX];
    jboolean gotJVMPath = GetJVMPath(jrePath, preferredJVM, jvmPath, sizeof(jvmPath), GetArch(), CURRENT_DATA_MODEL);
    if (!gotJVMPath) {
        JLI_ReportErrorMessage("Failed to GetJVMPath()");
        return NULL;
    }

    InvocationFunctions *fxns = malloc(sizeof(InvocationFunctions));
    jboolean vmLoaded = LoadJavaVM(jvmPath, fxns);
    if (!vmLoaded) {
        JLI_ReportErrorMessage("Failed to LoadJavaVM()");
        return NULL;
    }

    return sExportedJNIFunctions = fxns;
}

JNIEXPORT jint JNICALL
JNI_GetDefaultJavaVMInitArgs(void *args) {
    InvocationFunctions *ifn = GetExportedJNIFunctions();
    if (ifn == NULL) return JNI_ERR;
    return ifn->GetDefaultJavaVMInitArgs(args);
}

JNIEXPORT jint JNICALL
JNI_CreateJavaVM(JavaVM **pvm, void **penv, void *args) {
    InvocationFunctions *ifn = GetExportedJNIFunctions();
    if (ifn == NULL) return JNI_ERR;
    return ifn->CreateJavaVM(pvm, penv, args);
}

JNIEXPORT jint JNICALL
JNI_GetCreatedJavaVMs(JavaVM **vmBuf, jsize bufLen, jsize *nVMs) {
    InvocationFunctions *ifn = GetExportedJNIFunctions();
    if (ifn == NULL) return JNI_ERR;
    return ifn->GetCreatedJavaVMs(vmBuf, bufLen, nVMs);
}

/*
 * Allow JLI-aware launchers to specify a client/server preference
 */
JNIEXPORT void JNICALL
JLI_SetPreferredJVM(const char *prefJVM) {
    if (sPreferredJVMType != NULL) {
        free(sPreferredJVMType);
        sPreferredJVMType = NULL;
    }

    if (prefJVM == NULL) return;
    sPreferredJVMType = strdup(prefJVM);
}

static BOOL awtLoaded = NO;
static pthread_mutex_t awtLoaded_mutex = PTHREAD_MUTEX_INITIALIZER;
static pthread_cond_t  awtLoaded_cv = PTHREAD_COND_INITIALIZER;

JNIEXPORT void JNICALL
JLI_NotifyAWTLoaded()
{
    pthread_mutex_lock(&awtLoaded_mutex);
    awtLoaded = YES;
    pthread_cond_signal(&awtLoaded_cv);
    pthread_mutex_unlock(&awtLoaded_mutex);
}

static int (*main_fptr)(int argc, char **argv) = NULL;

/*
 * Unwrap the arguments and re-run main()
 */
static void *apple_main (void *arg)
{
    objc_registerThreadWithCollector();

    if (main_fptr == NULL) {
        main_fptr = (int (*)())dlsym(RTLD_DEFAULT, "main");
        if (main_fptr == NULL) {
            JLI_ReportErrorMessageSys("error locating main entrypoint\n");
            exit(1);
        }
    }

    struct NSAppArgs *args = (struct NSAppArgs *) arg;
    exit(main_fptr(args->argc, args->argv));
}

static void dummyTimer(CFRunLoopTimerRef timer, void *info) {}

static void ParkEventLoop() {
    // RunLoop needs at least one source, and 1e20 is pretty far into the future
    CFRunLoopTimerRef t = CFRunLoopTimerCreate(kCFAllocatorDefault, 1.0e20, 0.0, 0, 0, dummyTimer, NULL);
    CFRunLoopAddTimer(CFRunLoopGetCurrent(), t, kCFRunLoopDefaultMode);
    CFRelease(t);

    // Park this thread in the main run loop.
    int32_t result;
    do {
        result = CFRunLoopRunInMode(kCFRunLoopDefaultMode, 1.0e20, false);
    } while (result != kCFRunLoopRunFinished);
}

/*
 * Mac OS X mandates that the GUI event loop run on very first thread of
 * an application. This requires that we re-call Java's main() on a new
 * thread, reserving the 'main' thread for Cocoa.
 */
static void MacOSXStartup(int argc, char *argv[]) {
    // Thread already started?
    static jboolean started = false;
    if (started) {
        return;
    }
    started = true;

    // Hand off arguments
    struct NSAppArgs args;
    args.argc = argc;
    args.argv = argv;

    // Fire up the main thread
    pthread_t main_thr;
    if (pthread_create(&main_thr, NULL, &apple_main, &args) != 0) {
        JLI_ReportErrorMessageSys("Could not create main thread: %s\n", strerror(errno));
        exit(1);
    }
    if (pthread_detach(main_thr)) {
        JLI_ReportErrorMessageSys("pthread_detach() failed: %s\n", strerror(errno));
        exit(1);
    }

    ParkEventLoop();
}

void
CreateExecutionEnvironment(int *pargc, char ***pargv,
                           char jrepath[], jint so_jrepath,
                           char jvmpath[], jint so_jvmpath,
                           char jvmcfg[],  jint so_jvmcfg) {
  /*
   * First, determine if we are running the desired data model.  If we
   * are running the desired data model, all the error messages
   * associated with calling GetJREPath, ReadKnownVMs, etc. should be
   * output.  However, if we are not running the desired data model,
   * some of the errors should be suppressed since it is more
   * informative to issue an error message based on whether or not the
   * os/processor combination has dual mode capabilities.
   */
    jboolean jvmpathExists;

    /* Compute/set the name of the executable */
    SetExecname(*pargv);

    /* Check data model flags, and exec process, if needed */
    {
      char *arch        = (char *)GetArch(); /* like sparc or sparcv9 */
      char * jvmtype    = NULL;
      int  argc         = *pargc;
      char **argv       = *pargv;
      int running       = CURRENT_DATA_MODEL;

      int wanted        = running;      /* What data mode is being
                                           asked for? Current model is
                                           fine unless another model
                                           is asked for */

      char** newargv    = NULL;
      int    newargc    = 0;

      /*
       * Starting in 1.5, all unix platforms accept the -d32 and -d64
       * options.  On platforms where only one data-model is supported
       * (e.g. ia-64 Linux), using the flag for the other data model is
       * an error and will terminate the program.
       */

      { /* open new scope to declare local variables */
        int i;

        newargv = (char **)JLI_MemAlloc((argc+1) * sizeof(char*));
        newargv[newargc++] = argv[0];

        /* scan for data model arguments and remove from argument list;
           last occurrence determines desired data model */
        for (i=1; i < argc; i++) {

          if (JLI_StrCmp(argv[i], "-J-d64") == 0 || JLI_StrCmp(argv[i], "-d64") == 0) {
            wanted = 64;
            continue;
          }
          if (JLI_StrCmp(argv[i], "-J-d32") == 0 || JLI_StrCmp(argv[i], "-d32") == 0) {
            wanted = 32;
            continue;
          }
          newargv[newargc++] = argv[i];

          if (IsJavaArgs()) {
            if (argv[i][0] != '-') continue;
          } else {
            if (JLI_StrCmp(argv[i], "-classpath") == 0 || JLI_StrCmp(argv[i], "-cp") == 0) {
              i++;
              if (i >= argc) break;
              newargv[newargc++] = argv[i];
              continue;
            }
            if (argv[i][0] != '-') { i++; break; }
          }
        }

        /* copy rest of args [i .. argc) */
        while (i < argc) {
          newargv[newargc++] = argv[i++];
        }
        newargv[newargc] = NULL;

        /*
         * newargv has all proper arguments here
         */

        argc = newargc;
        argv = newargv;
      }

      /* If the data model is not changing, it is an error if the
         jvmpath does not exist */
      if (wanted == running) {
        /* Find out where the JRE is that we will be using. */
        if (!GetJREPath(jrepath, so_jrepath, arch, JNI_FALSE) ) {
          JLI_ReportErrorMessage(JRE_ERROR1);
          exit(2);
        }
        JLI_Snprintf(jvmcfg, so_jvmcfg, "%s%slib%s%s%sjvm.cfg",
          jrepath, FILESEP, FILESEP,  "", "");
        /* Find the specified JVM type */
        if (ReadKnownVMs(jvmcfg, JNI_FALSE) < 1) {
          JLI_ReportErrorMessage(CFG_ERROR7);
          exit(1);
        }

        jvmpath[0] = '\0';
        jvmtype = CheckJvmType(pargc, pargv, JNI_FALSE);
        if (JLI_StrCmp(jvmtype, "ERROR") == 0) {
            JLI_ReportErrorMessage(CFG_ERROR9);
            exit(4);
        }

        if (!GetJVMPath(jrepath, jvmtype, jvmpath, so_jvmpath, arch, wanted)) {
          JLI_ReportErrorMessage(CFG_ERROR8, jvmtype, jvmpath);
          exit(4);
        }

        /*
         * Mac OS X requires the Cocoa event loop to be run on the "main"
         * thread. Spawn off a new thread to run main() and pass
         * this thread off to the Cocoa event loop.
         */
        MacOSXStartup(argc, argv);

        /*
         * we seem to have everything we need, so without further ado
         * we return back, otherwise proceed to set the environment.
         */
        return;
      } else {  /* do the same speculatively or exit */
#if defined(DUAL_MODE)
        if (running != wanted) {
          /* Find out where the JRE is that we will be using. */
          if (!GetJREPath(jrepath, so_jrepath, GetArchPath(wanted), JNI_TRUE)) {
            /* give up and let other code report error message */
            JLI_ReportErrorMessage(JRE_ERROR2, wanted);
            exit(1);
          }
          JLI_Snprintf(jvmcfg, so_jvmcfg, "%s%slib%s%s%sjvm.cfg",
            jrepath, FILESEP, FILESEP,  "", "");
          /*
           * Read in jvm.cfg for target data model and process vm
           * selection options.
           */
          if (ReadKnownVMs(jvmcfg, JNI_TRUE) < 1) {
            /* give up and let other code report error message */
            JLI_ReportErrorMessage(JRE_ERROR2, wanted);
            exit(1);
          }
          jvmpath[0] = '\0';
          jvmtype = CheckJvmType(pargc, pargv, JNI_TRUE);
          if (JLI_StrCmp(jvmtype, "ERROR") == 0) {
            JLI_ReportErrorMessage(CFG_ERROR9);
            exit(4);
          }

          /* exec child can do error checking on the existence of the path */
          jvmpathExists = GetJVMPath(jrepath, jvmtype, jvmpath, so_jvmpath, GetArchPath(wanted), wanted);
        }
#else /* ! DUAL_MODE */
        JLI_ReportErrorMessage(JRE_ERROR2, wanted);
        exit(1);
#endif /* DUAL_MODE */
        }
        {
            char *newexec = execname;
            JLI_TraceLauncher("TRACER_MARKER:About to EXEC\n");
            (void) fflush(stdout);
            (void) fflush(stderr);
            /*
            * Use posix_spawn() instead of execv() on Mac OS X.
            * This allows us to choose which architecture the child process
            * should run as.
            */
            {
                posix_spawnattr_t attr;
                size_t unused_size;
                pid_t  unused_pid;

#if defined(__i386__) || defined(__x86_64__)
                cpu_type_t cpu_type[] = { (wanted == 64) ? CPU_TYPE_X86_64 : CPU_TYPE_X86,
                                    (running== 64) ? CPU_TYPE_X86_64 : CPU_TYPE_X86 };
#else
                cpu_type_t cpu_type[] = { CPU_TYPE_ANY };
#endif /* __i386 .. */

                posix_spawnattr_init(&attr);
                posix_spawnattr_setflags(&attr, POSIX_SPAWN_SETEXEC);
                posix_spawnattr_setbinpref_np(&attr, sizeof(cpu_type) / sizeof(cpu_type_t),
                                            cpu_type, &unused_size);

                posix_spawn(&unused_pid, newexec, NULL, &attr, argv, environ);
            }
            JLI_ReportErrorMessageSys(JRE_ERROR4, newexec);

#if defined(DUAL_MODE)
            if (running != wanted) {
                JLI_ReportErrorMessage(JRE_ERROR5, wanted, running);
            }
#endif /* DUAL_MODE */
        }
        exit(1);
    }
}

/*
 * VM choosing is done by the launcher (java.c).
 */
static jboolean
GetJVMPath(const char *jrepath, const char *jvmtype,
           char *jvmpath, jint jvmpathsize, const char * arch, int bitsWanted)
{
    struct stat s;

    if (JLI_StrChr(jvmtype, '/')) {
        JLI_Snprintf(jvmpath, jvmpathsize, "%s/" JVM_DLL, jvmtype);
    } else {
        /*
         * macosx client library is built thin, i386 only.
         * 64 bit client requests must load server library
         */
        const char *jvmtypeUsed = ((bitsWanted == 64) && (strcmp(jvmtype, "client") == 0)) ? "server" : jvmtype;
        JLI_Snprintf(jvmpath, jvmpathsize, "%s/lib/%s/" JVM_DLL, jrepath, jvmtypeUsed);
    }

    JLI_TraceLauncher("Does `%s' exist ... ", jvmpath);

    if (stat(jvmpath, &s) == 0) {
        JLI_TraceLauncher("yes.\n");
        return JNI_TRUE;
    } else {
        JLI_TraceLauncher("no.\n");
        return JNI_FALSE;
    }
}

/*
 * Find path to JRE based on .exe's location or registry settings.
 */
static jboolean
GetJREPath(char *path, jint pathsize, const char * arch, jboolean speculative)
{
    char libjava[MAXPATHLEN];

    if (GetApplicationHome(path, pathsize)) {
        /* Is JRE co-located with the application? */
        JLI_Snprintf(libjava, sizeof(libjava), "%s/lib/" JAVA_DLL, path);
        if (access(libjava, F_OK) == 0) {
            return JNI_TRUE;
        }

        /* Does the app ship a private JRE in <apphome>/jre directory? */
        JLI_Snprintf(libjava, sizeof(libjava), "%s/jre/lib/" JAVA_DLL, path);
        if (access(libjava, F_OK) == 0) {
            JLI_StrCat(path, "/jre");
            JLI_TraceLauncher("JRE path is %s\n", path);
            return JNI_TRUE;
        }
    }

    /* try to find ourselves instead */
    Dl_info selfInfo;
    dladdr(&GetJREPath, &selfInfo);

    char *realPathToSelf = realpath(selfInfo.dli_fname, path);
    if (realPathToSelf != path) {
        return JNI_FALSE;
    }

    size_t pathLen = strlen(realPathToSelf);
    if (pathLen == 0) {
        return JNI_FALSE;
    }

    const char lastPathComponent[] = "/lib/jli/libjli.dylib";
    size_t sizeOfLastPathComponent = sizeof(lastPathComponent) - 1;
    if (pathLen < sizeOfLastPathComponent) {
        return JNI_FALSE;
    }

    size_t indexOfLastPathComponent = pathLen - sizeOfLastPathComponent;
    if (0 == strncmp(realPathToSelf + indexOfLastPathComponent, lastPathComponent, sizeOfLastPathComponent - 1)) {
        realPathToSelf[indexOfLastPathComponent + 1] = '\0';
        return JNI_TRUE;
    }

    if (!speculative)
      JLI_ReportErrorMessage(JRE_ERROR8 JAVA_DLL);
    return JNI_FALSE;
}

jboolean
LoadJavaVM(const char *jvmpath, InvocationFunctions *ifn)
{
    Dl_info dlinfo;
    void *libjvm;

    JLI_TraceLauncher("JVM path is %s\n", jvmpath);

    libjvm = dlopen(jvmpath, RTLD_NOW + RTLD_GLOBAL);
    if (libjvm == NULL) {
        JLI_ReportErrorMessage(DLL_ERROR1, __LINE__);
        JLI_ReportErrorMessage(DLL_ERROR2, jvmpath, dlerror());
        return JNI_FALSE;
    }

    ifn->CreateJavaVM = (CreateJavaVM_t)
        dlsym(libjvm, "JNI_CreateJavaVM");
    if (ifn->CreateJavaVM == NULL) {
        JLI_ReportErrorMessage(DLL_ERROR2, jvmpath, dlerror());
        return JNI_FALSE;
    }

    ifn->GetDefaultJavaVMInitArgs = (GetDefaultJavaVMInitArgs_t)
        dlsym(libjvm, "JNI_GetDefaultJavaVMInitArgs");
    if (ifn->GetDefaultJavaVMInitArgs == NULL) {
        JLI_ReportErrorMessage(DLL_ERROR2, jvmpath, dlerror());
        return JNI_FALSE;
    }

    ifn->GetCreatedJavaVMs = (GetCreatedJavaVMs_t)
    dlsym(libjvm, "JNI_GetCreatedJavaVMs");
    if (ifn->GetCreatedJavaVMs == NULL) {
        JLI_ReportErrorMessage(DLL_ERROR2, jvmpath, dlerror());
        return JNI_FALSE;
    }

    return JNI_TRUE;
}

/*
 * Compute the name of the executable
 *
 * In order to re-exec securely we need the absolute path of the
 * executable. On Solaris getexecname(3c) may not return an absolute
 * path so we use dladdr to get the filename of the executable and
 * then use realpath to derive an absolute path. From Solaris 9
 * onwards the filename returned in DL_info structure from dladdr is
 * an absolute pathname so technically realpath isn't required.
 * On Linux we read the executable name from /proc/self/exe.
 * As a fallback, and for platforms other than Solaris and Linux,
 * we use FindExecName to compute the executable name.
 */
const char*
SetExecname(char **argv)
{
    char* exec_path = NULL;
    {
        Dl_info dlinfo;
        int (*fptr)();

        fptr = (int (*)())dlsym(RTLD_DEFAULT, "main");
        if (fptr == NULL) {
            JLI_ReportErrorMessage(DLL_ERROR3, dlerror());
            return JNI_FALSE;
        }

        if (dladdr((void*)fptr, &dlinfo)) {
            char *resolved = (char*)JLI_MemAlloc(PATH_MAX+1);
            if (resolved != NULL) {
                exec_path = realpath(dlinfo.dli_fname, resolved);
                if (exec_path == NULL) {
                    JLI_MemFree(resolved);
                }
            }
        }
    }
    if (exec_path == NULL) {
        exec_path = FindExecName(argv[0]);
    }
    execname = exec_path;
    return exec_path;
}

/*
 * BSD's implementation of CounterGet()
 */
int64_t
CounterGet()
{
    struct timeval tv;
    gettimeofday(&tv, NULL);
    return (tv.tv_sec * 1000) + tv.tv_usec;
}


/* --- Splash Screen shared library support --- */

static JavaVM* SetJavaVMValue()
{
    JavaVM * jvm = NULL;

    // The handle is good for both the launcher and the libosxapp.dylib
    void * handle = dlopen(NULL, RTLD_LAZY | RTLD_GLOBAL);
    if (handle) {
        typedef JavaVM* (*JLI_GetJavaVMInstance_t)();

        JLI_GetJavaVMInstance_t JLI_GetJavaVMInstance =
            (JLI_GetJavaVMInstance_t)dlsym(handle,
                    "JLI_GetJavaVMInstance");
        if (JLI_GetJavaVMInstance) {
            jvm = JLI_GetJavaVMInstance();
        }

        if (jvm) {
            typedef void (*OSXAPP_SetJavaVM_t)(JavaVM*);

            OSXAPP_SetJavaVM_t OSXAPP_SetJavaVM =
                (OSXAPP_SetJavaVM_t)dlsym(handle, "OSXAPP_SetJavaVM");
            if (OSXAPP_SetJavaVM) {
                OSXAPP_SetJavaVM(jvm);
            } else {
                jvm = NULL;
            }
        }

        dlclose(handle);
    }

    return jvm;
}

static const char* SPLASHSCREEN_SO = JNI_LIB_NAME("splashscreen");

static void* hSplashLib = NULL;

void* SplashProcAddress(const char* name) {
    if (!hSplashLib) {
        char jrePath[PATH_MAX];
        if (!GetJREPath(jrePath, sizeof(jrePath), GetArch(), JNI_FALSE)) {
            JLI_ReportErrorMessage(JRE_ERROR1);
            return NULL;
        }

        char splashPath[PATH_MAX];
        const int ret = JLI_Snprintf(splashPath, sizeof(splashPath),
                "%s/lib/%s", jrePath, SPLASHSCREEN_SO);
        if (ret >= (int)sizeof(splashPath)) {
            JLI_ReportErrorMessage(JRE_ERROR11);
            return NULL;
        }
        if (ret < 0) {
            JLI_ReportErrorMessage(JRE_ERROR13);
            return NULL;
        }

        hSplashLib = dlopen(splashPath, RTLD_LAZY | RTLD_GLOBAL);
        // It's OK if dlopen() fails. The splash screen library binary file
        // might have been stripped out from the JRE image to reduce its size
        // (e.g. on embedded platforms).

        if (hSplashLib) {
            if (!SetJavaVMValue()) {
                dlclose(hSplashLib);
                hSplashLib = NULL;
            }
        }
    }
    if (hSplashLib) {
        void* sym = dlsym(hSplashLib, name);
        return sym;
    } else {
        return NULL;
    }
}

void SplashFreeLibrary() {
    if (hSplashLib) {
        dlclose(hSplashLib);
        hSplashLib = NULL;
    }
}

/*
 * Block current thread and continue execution in a new thread
 */
int
ContinueInNewThread0(int (JNICALL *continuation)(void *), jlong stack_size, void * args) {
    int rslt;
    pthread_t tid;
    pthread_attr_t attr;
    pthread_attr_init(&attr);
    pthread_attr_setdetachstate(&attr, PTHREAD_CREATE_JOINABLE);

    if (stack_size > 0) {
      pthread_attr_setstacksize(&attr, stack_size);
    }

    if (pthread_create(&tid, &attr, (void *(*)(void*))continuation, (void*)args) == 0) {
      void * tmp;
      pthread_join(tid, &tmp);
      rslt = (int)tmp;
    } else {
     /*
      * Continue execution in current thread if for some reason (e.g. out of
      * memory/LWP)  a new thread can't be created. This will likely fail
      * later in continuation as JNI_CreateJavaVM needs to create quite a
      * few new threads, anyway, just give it a try..
      */
      rslt = continuation(args);
    }

    pthread_attr_destroy(&attr);
    return rslt;
}

void SetJavaLauncherPlatformProps() {
   /* Linux only */
}

jboolean
ServerClassMachine(void) {
    return JNI_TRUE;
}

static JavaVM* jvmInstance = NULL;
static jboolean sameThread = JNI_FALSE; /* start VM in current thread */

/*
 * Note there is a callback on this function from the splashscreen logic,
 * this as well SetJavaVMValue() needs to be simplified.
 */
JavaVM*
JLI_GetJavaVMInstance()
{
    return jvmInstance;
}

void
RegisterThread()
{
    objc_registerThreadWithCollector();
}

static void
SetXDockArgForAWT(const char *arg)
{
    char envVar[80];
    if (strstr(arg, "-Xdock:name=") == arg) {
        /*
         * The APP_NAME_<pid> environment variable is used to pass
         * an application name as specified with the -Xdock:name command
         * line option from Java launcher code to the AWT code in order
         * to assign this name to the app's dock tile on the Mac.
         * The _<pid> part is added to avoid collisions with child processes.
         *
         * WARNING: This environment variable is an implementation detail and
         * isn't meant for use outside of the core platform. The mechanism for
         * passing this information from Java launcher to other modules may
         * change drastically between update release, and it may even be
         * removed or replaced with another mechanism.
         *
         * NOTE: It is used by SWT, and JavaFX.
         */
        snprintf(envVar, sizeof(envVar), "APP_NAME_%d", getpid());
        setenv(envVar, (arg + 12), 1);
    }

    if (strstr(arg, "-Xdock:icon=") == arg) {
        /*
         * The APP_ICON_<pid> environment variable is used to pass
         * an application icon as specified with the -Xdock:icon command
         * line option from Java launcher code to the AWT code in order
         * to assign this icon to the app's dock tile on the Mac.
         * The _<pid> part is added to avoid collisions with child processes.
         *
         * WARNING: This environment variable is an implementation detail and
         * isn't meant for use outside of the core platform. The mechanism for
         * passing this information from Java launcher to other modules may
         * change drastically between update release, and it may even be
         * removed or replaced with another mechanism.
         *
         * NOTE: It is used by SWT, and JavaFX.
         */
        snprintf(envVar, sizeof(envVar), "APP_ICON_%d", getpid());
        setenv(envVar, (arg + 12), 1);
    }
}

static void
SetMainClassForAWT(JNIEnv *env, jclass mainClass) {
    jclass classClass = NULL;
    NULL_CHECK(classClass = FindBootStrapClass(env, "java/lang/Class"));

    jmethodID getCanonicalNameMID = NULL;
    NULL_CHECK(getCanonicalNameMID = (*env)->GetMethodID(env, classClass, "getCanonicalName", "()Ljava/lang/String;"));

    jstring mainClassString = NULL;
    NULL_CHECK(mainClassString = (*env)->CallObjectMethod(env, mainClass, getCanonicalNameMID));

    const char *mainClassName = NULL;
    NULL_CHECK(mainClassName = (*env)->GetStringUTFChars(env, mainClassString, NULL));

    char envVar[80];
    /*
     * The JAVA_MAIN_CLASS_<pid> environment variable is used to pass
     * the name of a Java class whose main() method is invoked by
     * the Java launcher code to start the application, to the AWT code
     * in order to assign the name to the Apple menu bar when the app
     * is active on the Mac.
     * The _<pid> part is added to avoid collisions with child processes.
     *
     * WARNING: This environment variable is an implementation detail and
     * isn't meant for use outside of the core platform. The mechanism for
     * passing this information from Java launcher to other modules may
     * change drastically between update release, and it may even be
     * removed or replaced with another mechanism.
     *
     * NOTE: It is used by SWT, and JavaFX.
     */
    snprintf(envVar, sizeof(envVar), "JAVA_MAIN_CLASS_%d", getpid());
    setenv(envVar, mainClassName, 1);

    (*env)->ReleaseStringUTFChars(env, mainClassString, mainClassName);
}

void
SetXStartOnFirstThreadArg()
{
    // XXX: BEGIN HACK
    // short circuit hack for <https://bugs.eclipse.org/bugs/show_bug.cgi?id=211625>
    // need a way to get AWT/Swing apps launched when spawned from Eclipse,
    // which currently has no UI to not pass the -XstartOnFirstThread option
    if (getenv("HACK_IGNORE_START_ON_FIRST_THREAD") != NULL) return;
    // XXX: END HACK

    sameThread = JNI_TRUE;
    // Set a variable that tells us we started on the main thread.
    // This is used by the AWT during startup. (See awt.m)
    char envVar[80];
    snprintf(envVar, sizeof(envVar), "JAVA_STARTED_ON_FIRST_THREAD_%d", getpid());
    setenv(envVar, "1", 1);
}

/* This class is made for performSelectorOnMainThread when java main
 * should be launched on main thread.
 * We cannot use dispatch_sync here, because it blocks the main dispatch queue
 * which is used inside Cocoa
 */
@interface JavaLaunchHelper : NSObject {
    int _returnValue;
}
- (void) launchJava:(NSValue*)argsValue;
- (int) getReturnValue;
@end

@implementation JavaLaunchHelper

- (void) launchJava:(NSValue*)argsValue
{
    _returnValue = JavaMain([argsValue pointerValue]);
}

- (int) getReturnValue
{
    return _returnValue;
}

@end

// MacOSX we may continue in the same thread
int
JVMInit(InvocationFunctions* ifn, jlong threadStackSize,
                 int argc, char **argv,
                 int mode, char *what, int ret) {
    if (sameThread) {
        JLI_TraceLauncher("In same thread\n");
        // need to block this thread against the main thread
        // so signals get caught correctly
        JavaMainArgs args;
        args.argc = argc;
        args.argv = argv;
        args.mode = mode;
        args.what = what;
        args.ifn  = *ifn;
        int rslt;
        NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init];
        {
            JavaLaunchHelper* launcher = [[[JavaLaunchHelper alloc] init] autorelease];
            [launcher performSelectorOnMainThread:@selector(launchJava:)
                                       withObject:[NSValue valueWithPointer:(void*)&args]
                                    waitUntilDone:YES];
            rslt = [launcher getReturnValue];
        }
        [pool drain];
        return rslt;
    } else {
        return ContinueInNewThread(ifn, threadStackSize, argc, argv, mode, what, ret);
    }
}

/*
 * Note the jvmInstance must be initialized first before entering into
 * ShowSplashScreen, as there is a callback into the JLI_GetJavaVMInstance.
 */
void PostJVMInit(JNIEnv *env, jstring mainClass, JavaVM *vm) {
    jvmInstance = vm;
    SetMainClassForAWT(env, mainClass);
    ShowSplashScreen();
}

jboolean
ProcessPlatformOption(const char* arg)
{
    if (JLI_StrCmp(arg, "-XstartOnFirstThread") == 0) {
       SetXStartOnFirstThreadArg();
       return JNI_TRUE;
    } else if (JLI_StrCCmp(arg, "-Xdock:") == 0) {
       SetXDockArgForAWT(arg);
       return JNI_TRUE;
    }
    // arguments we know not
    return JNI_FALSE;
}

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