8157986: Runtime support for javac to determine arguments to the runtime environment

Reviewed-by: alanb

jdk/make/mapfiles/libjava/mapfile-vers

@@ -267,6 +267,7 @@ SUNWprivate_1.1 {
                 Java_jdk_internal_misc_VM_geteuid;
                 Java_jdk_internal_misc_VM_getgid;
                 Java_jdk_internal_misc_VM_getegid;
+                Java_jdk_internal_misc_VM_getRuntimeArguments;
                 Java_jdk_internal_misc_VM_initialize;
 
                 Java_java_lang_reflect_Module_defineModule0;

jdk/src/java.base/share/classes/jdk/internal/misc/VM.java

@@ -475,6 +475,23 @@ public class VM {
      */
     public static native long getNanoTimeAdjustment(long offsetInSeconds);
 
+    /**
+     * Returns the VM arguments for this runtime environment.
+     *
+     * @implNote
+     * The HotSpot JVM processes the input arguments from multiple sources
+     * in the following order:
+     * 1. JAVA_TOOL_OPTIONS environment variable
+     * 2. Options from JNI Invocation API
+     * 3. _JAVA_OPTIONS environment variable
+     *
+     * If VM options file is specified via -XX:VMOptionsFile, the vm options
+     * file is read and expanded in place of -XX:VMOptionFile option.
+     *
+     * Open issue with -XX:Flags (see JDK-8157979)
+     */
+    public static native String[] getRuntimeArguments();
+
     static {
         initialize();
     }

jdk/src/java.base/share/classes/module-info.java

@@ -165,6 +165,7 @@ module java.base {
         java.sql,
         java.xml,
         jdk.charsets,
+        jdk.compiler,
         jdk.jartool,
         jdk.jlink,
         jdk.net,

jdk/src/java.base/share/native/libjava/VM.c

@@ -55,3 +55,8 @@ Java_jdk_internal_misc_VM_initialize(JNIEnv *env, jclass cls) {
     (*env)->RegisterNatives(env, cls,
                             methods, sizeof(methods)/sizeof(methods[0]));
 }
+
+JNIEXPORT jobjectArray JNICALL
+Java_jdk_internal_misc_VM_getRuntimeArguments(JNIEnv *env, jclass cls) {
+    return JVM_GetVmArguments(env);
+}