《jdk8u源码分析》6.CreateExecutionEnvironment

src/windows/bin/java_md.c::CreateExecutionEnvironment

/*
 *
 */
void
CreateExecutionEnvironment(int *pargc, char ***pargv,
                           char *jrepath, jint so_jrepath,
                           char *jvmpath, jint so_jvmpath,
                           char *jvmcfg,  jint so_jvmcfg) {
    char * jvmtype;
    int i = 0;
    int running = CURRENT_DATA_MODEL;

    int wanted = running;

    char** argv = *pargv;
    for (i = 1; i < *pargc ; i++) {
    	//根据-J-d64/-J-d32判定用户准备运行的虚拟机是64位还是32位
        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;
        }
		//IsJavaArgs()依据JAVA_ARGS是否定义(编译时生成： make/CompileLaunchers.gmk)
		//快速过滤java命令行参数
		//argv默认前面都是以'-'开始的java可选参数，自定义参数在java可选参数后
        if (IsJavaArgs() && argv[i][0] != '-')
            continue;
        if (argv[i][0] != '-')
            break;
    }
    //如果目标运行环境与当前运行环境不匹配，打印异常信息
    if (running != wanted) {
    	//"Error: This Java instance does not support a %d-bit JVM.\nPlease install the desired version."
        JLI_ReportErrorMessage(JRE_ERROR2, wanted);
        exit(1);
    }

    /* Find out where the JRE is that we will be using. */
    
    if (!GetJREPath(jrepath, so_jrepath)) {
    	//"Error: Could not find Java SE Runtime Environment."
        JLI_ReportErrorMessage(JRE_ERROR1);
        exit(2);
    }

	//加载jvm.cfg配置文件
	//%JRE_HOME%\lib\${arch:amd64}\jvm.cfg
    JLI_Snprintf(jvmcfg, so_jvmcfg, "%s%slib%s%s%sjvm.cfg",
        jrepath, FILESEP, FILESEP, (char*)GetArch(), FILESEP);

    /* Find the specified JVM type */
    //读取jvm.cfg到：
    //static struct vmdesc *knownVMs = NULL;
    if (ReadKnownVMs(jvmcfg, JNI_FALSE) < 1) {
    	//"Error: no known VMs. (check for corrupt jvm.cfg file)"
        JLI_ReportErrorMessage(CFG_ERROR7);
        exit(1);
    }
	
	//过滤命令行参数，获取jvm type
    jvmtype = CheckJvmType(pargc, pargv, JNI_FALSE);
    //如果jvmtype所在配置的flag为：VM_ERROR，打印错误信息并退出进程
    if (JLI_StrCmp(jvmtype, "ERROR") == 0) {
    	//"Error: could not determine JVM type."
        JLI_ReportErrorMessage(CFG_ERROR9);
        exit(4);
    }

    jvmpath[0] = '\0';
    //拼接jvmpath: %JRE_HOME%\\bin\\${jvmtype}\\java.dll
    //如果文件不存在，打印错误信息，并退出进程
    if (!GetJVMPath(jrepath, jvmtype, jvmpath, so_jvmpath)) {
    	//"Error: missing `%s' JVM at `%s'.\nPlease install or use the JRE or JDK that contains these missing components."
        JLI_ReportErrorMessage(CFG_ERROR8, jvmtype, jvmpath);
        exit(4);
    }
    /* If we got here, jvmpath has been correctly initialized. */

    /* Check if we need preload AWT */
#ifdef ENABLE_AWT_PRELOAD
    argv = *pargv;
    for (i = 0; i < *pargc ; i++) {
        /* Tests the "turn on" parameter only if not set yet. */
        if (awtPreloadD3D < 0) {
            if (GetBoolParamValue(PARAM_PRELOAD_D3D, argv[i]) == 1) {
                awtPreloadD3D = 1;
            }
        }
        /* Test parameters which can disable preloading if not already disabled. */
        if (awtPreloadD3D != 0) {
            if (GetBoolParamValue(PARAM_NODDRAW, argv[i]) == 1
                || GetBoolParamValue(PARAM_D3D, argv[i]) == 0
                || GetBoolParamValue(PARAM_OPENGL, argv[i]) == 1)
            {
                awtPreloadD3D = 0;
                /* no need to test the rest of the parameters */
                break;
            }
        }
    }
#endif /* ENABLE_AWT_PRELOAD */
}

src/share/bin/java.h

//取决于编译器目标平台的ABI（应用程序二进制接口）
#define CURRENT_DATA_MODEL (CHAR_BIT * sizeof(void*))

src/share/bin/java.h

#define GetArch() GetArchPath(CURRENT_DATA_MODEL)

src/windows/bin/java_md.c(Windows)

/*
 * Returns the arch path, to get the current arch use the
 * macro GetArch, nbits here is ignored for now.
 */
const char *
GetArchPath(int nbits)
{
#ifdef _M_AMD64
    return "amd64";
#elif defined(_M_IA64)
    return "ia64";
#else
    return "i386";
#endif
}

src/solaris/bin/java_md_solinux.c(Linux)

const char *
GetArchPath(int nbits)
{
    switch(nbits) {
#ifdef DUAL_MODE
        case 32:
            return LIBARCH32NAME;
        case 64:
            return LIBARCH64NAME;
#endif /* DUAL_MODE */
        default:
            return LIBARCHNAME;
    }
}

src/macosx/bin/java_md_macosx.c(Mac)

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

%JRE_HOME%\lib${arch}\jvm.cfg

#
# 
# 
# Copyright (c) 2003, 2013, Oracle and/or its affiliates. All rights reserved.
# ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
#
#
#
#
#
#
#
#
#
#
#
#
#
#
#
#
#
#
#
#
#
#
# List of JVMs that can be used as an option to java, javac, etc.
# Order is important -- first in this list is the default JVM.
# NOTE that this both this file and its format are UNSUPPORTED and
# WILL GO AWAY in a future release.
#
# You may also select a JVM in an arbitrary location with the
# "-XXaltjvm=<jvm_dir>" option, but that too is unsupported
# and may not be available in a future release.
#
-server KNOWN
-client IGNORE