Java源码-0x05-宏定义

1 宏定义

宏定义着实太多，甚至有的嵌套地太深，只能遇到了就记录一下

当然了，很多宏的定义都是跨平台的，所以以linux+gcc的环境为例

• JNIEXPORT

• JNICALL

• JVM_ENTRY

• JVM_END

1.1 JNIEXPORT

1.2 JNICALL

#define JNICALL

1.3 JVM_ENTRY

#define JVM_ENTRY(result_type, header)                               \
extern "C" {                                                         \
  result_type JNICALL header {                                       \
    JavaThread* thread=JavaThread::thread_from_jni_environment(env); \
    ThreadInVMfromNative __tiv(thread);                              \
    debug_only(VMNativeEntryWrapper __vew;)                          \
    VM_ENTRY_BASE(result_type, header, thread)

1.4 JVM_END

#define JVM_END } }

2 示例

2.1 JNIEXPORT和JNICALL

JNIEXPORT void JNICALL
JVM_MonitorWait(JNIEnv *env, jobject obj, jlong ms);

替换为

__attribute__((visibility("default")))
void JVM_MonitorWait(JNIEnv *env, jobject obj, jlong ms);

2.2 JVM_ENTRY和JVM_END

JVM_ENTRY(void, JVM_MonitorWait(JNIEnv* env, jobject handle, jlong ms))
  JVMWrapper("JVM_MonitorWait");
  Handle obj(THREAD, JNIHandles::resolve_non_null(handle));
  JavaThreadInObjectWaitState jtiows(thread, ms != 0);
  if (JvmtiExport::should_post_monitor_wait()) {
    JvmtiExport::post_monitor_wait((JavaThread *)THREAD, (oop)obj(), ms);

    // The current thread already owns the monitor and it has not yet
    // been added to the wait queue so the current thread cannot be
    // made the successor. This means that the JVMTI_EVENT_MONITOR_WAIT
    // event handler cannot accidentally consume an unpark() meant for
    // the ParkEvent associated with this ObjectMonitor.
  }
  ObjectSynchronizer::wait(obj, ms, CHECK);
JVM_END

替换为

extern "C" {
  void JVM_MonitorWait(JNIEnv* env, jobject handle, jlong ms))
  {
    JavaThread* thread=JavaThread::thread_from_jni_environment(env);
    ThreadInVMfromNative __tiv(thread);
    debug_only(VMNativeEntryWrapper __vew;)
    VM_ENTRY_BASE(result_type, header, thread)
  JVMWrapper("JVM_MonitorWait");
  Handle obj(THREAD, JNIHandles::resolve_non_null(handle));
  JavaThreadInObjectWaitState jtiows(thread, ms != 0);
  if (JvmtiExport::should_post_monitor_wait())
  {
    JvmtiExport::post_monitor_wait((JavaThread *)THREAD, (oop)obj(), ms);

    // The current thread already owns the monitor and it has not yet
    // been added to the wait queue so the current thread cannot be
    // made the successor. This means that the JVMTI_EVENT_MONITOR_WAIT
    // event handler cannot accidentally consume an unpark() meant for
    // the ParkEvent associated with this ObjectMonitor.
  }
  ObjectSynchronizer::wait(obj, ms, CHECK);
  }
}