gcc/libjava/resolve.cc

// resolve.cc - Code for linking and resolving classes and pool entries.

/* Copyright (C) 1999  Cygnus Solutions

   This file is part of libgcj.

This software is copyrighted work licensed under the terms of the
Libgcj License.  Please consult the file "LIBGCJ_LICENSE" for
details.  */

/* Author: Kresten Krab Thorup <krab@gnu.org>  */

#include <java-interp.h>

#include <cni.h>
#include <jvm.h>
#include <string.h>
#include <java-cpool.h>
#include <java/lang/Class.h>
#include <java/lang/String.h>
#include <java/lang/Thread.h>
#include <java/lang/InternalError.h>
#include <java/lang/VirtualMachineError.h>
#include <java/lang/NoSuchFieldError.h>
#include <java/lang/ClassFormatError.h>
#include <java/lang/IllegalAccessError.h>
#include <java/lang/AbstractMethodError.h>
#include <java/lang/ClassNotFoundException.h>
#include <java/lang/IncompatibleClassChangeError.h>

#ifdef INTERPRETER

static void throw_internal_error (char *msg)
	__attribute__ ((__noreturn__));
static void throw_class_format_error (jstring msg)
	__attribute__ ((__noreturn__));
static void throw_class_format_error (char *msg)
	__attribute__ ((__noreturn__));

#define StringClass _CL_Q34java4lang6String
extern java::lang::Class StringClass;
#define ClassObject _CL_Q34java4lang6Object
extern java::lang::Class ClassObject;
#define ObjectClass _CL_Q34java4lang6Object
extern java::lang::Class ObjectClass;


static int get_alignment_from_class (jclass);

static _Jv_ResolvedMethod* 
_Jv_BuildResolvedMethod (_Jv_Method*,
			 jclass,
			 jboolean,
			 jint);


static const int PUBLIC       = 0x001;
static const int PRIVATE      = 0x002;
static const int PROTECTED    = 0x004;
static const int STATIC       = 0x008;
static const int FINAL        = 0x010;
static const int SYNCHRONIZED = 0x020;
static const int VOLATILE     = 0x040;
static const int TRANSIENT    = 0x080;
static const int NATIVE       = 0x100;
static const int INTERFACE    = 0x200;
static const int ABSTRACT     = 0x400;
static const int ALL_FLAGS    = 0x7FF; 

// We need to know the name of a constructor.
static _Jv_Utf8Const *init_name = _Jv_makeUtf8Const ("<init>", 6);

static void throw_incompatible_class_change_error (jstring msg)
{
  JvThrow (new java::lang::IncompatibleClassChangeError (msg));
}

_Jv_word
_Jv_ResolvePoolEntry (jclass klass, int index)
{
  _Jv_Constants *pool = &klass->constants;

  if ((pool->tags[index] & JV_CONSTANT_ResolvedFlag) != 0)
    return pool->data[index];

  switch (pool->tags[index]) {
  case JV_CONSTANT_Class:
    {
      _Jv_Utf8Const *name = pool->data[index].utf8;

      jclass found;
      if (name->data[0] == '[')
	found = _Jv_FindClassFromSignature (&name->data[0],
					    klass->loader);
      else
	found = _Jv_FindClass (name, klass->loader);

      if (! found)
	{
	  jstring str = _Jv_NewStringUTF (name->data);
	  JvThrow (new java::lang::ClassNotFoundException (str));
	}

      if ((found->accflags & PUBLIC) == PUBLIC
	  || (_Jv_ClassNameSamePackage (found->name,
					klass->name)))
	{
	  pool->data[index].clazz = found;
	  pool->tags[index] |= JV_CONSTANT_ResolvedFlag;
	}
      else
	{
	  JvThrow (new java::lang::IllegalAccessError (found->getName()));
	}
    }
    break;

  case JV_CONSTANT_String:
    {
      jstring str;
      str = _Jv_NewStringUtf8Const (pool->data[index].utf8);
      pool->data[index].o = str;
      pool->tags[index] |= JV_CONSTANT_ResolvedFlag;
    }
    break;


  case JV_CONSTANT_Fieldref:
    {
      _Jv_ushort class_index, name_and_type_index;
      _Jv_loadIndexes (&pool->data[index],
		       class_index,
		       name_and_type_index);
      jclass owner = (_Jv_ResolvePoolEntry (klass, class_index)).clazz;

      if (owner != klass)
	_Jv_InitClass (owner);

      _Jv_ushort name_index, type_index;
      _Jv_loadIndexes (&pool->data[name_and_type_index],
		       name_index,
		       type_index);

      _Jv_Utf8Const *field_name = pool->data[name_index].utf8;
      _Jv_Utf8Const *field_type_name = pool->data[type_index].utf8;

      // FIXME: The implementation of this function
      // (_Jv_FindClassFromSignature) will generate an instance of
      // _Jv_Utf8Const for each call if the field type is a class name
      // (Lxx.yy.Z;).  This may be too expensive to do for each and
      // every fieldref being resolved.  For now, we fix the problem by
      // only doing it when we have a loader different from the class
      // declaring the field.

      jclass field_type = 0;

      if (owner->loader != klass->loader)
	field_type = _Jv_FindClassFromSignature (field_type_name->data,
						 klass->loader);
      
      _Jv_Field* the_field = 0;

      for (jclass cls = owner; cls != 0; cls = cls->getSuperclass ())
	{
	  for (int i = 0;  i < cls->field_count;  i++)
	    {
	      _Jv_Field *field = &cls->fields[i];
	      if (! _Jv_equalUtf8Consts (field->name, field_name))
		continue;

	      // now, check field access. 

	      if (   (cls == klass)
		  || ((field->flags & PUBLIC) != 0)
		  || (((field->flags & PROTECTED) != 0)
		      && cls->isAssignableFrom (klass))
		  || (((field->flags & PRIVATE) == 0)
		      && _Jv_ClassNameSamePackage (cls->name,
						   klass->name)))
		{
		  /* resove the field using the class' own loader
		     if necessary */

		  if (!field->isResolved ())
		    _Jv_ResolveField (field, cls->loader);

		  if (field_type != 0 && field->type != field_type)
		    JvThrow
		      (new java::lang::LinkageError
		       (JvNewStringLatin1 
			("field type mismatch with different loaders")));

		  the_field = field;
		  goto end_of_field_search;
		}
	      else
		{
		  JvThrow (new java::lang::IllegalAccessError);
		}
	    }
	}

    end_of_field_search:
      if (the_field == 0)
	{
	  jstring msg = JvNewStringLatin1 ("field ");
	  msg = msg->concat (owner->getName ());
	  msg = msg->concat (JvNewStringLatin1("."));
	  msg = msg->concat (_Jv_NewStringUTF (field_name->data));
	  msg = msg->concat (JvNewStringLatin1(" was not found."));
	  throw_incompatible_class_change_error (msg);
	}

      pool->data[index].field = the_field;
      pool->tags[index] |= JV_CONSTANT_ResolvedFlag;
    }
    break;

  case JV_CONSTANT_Methodref:
  case JV_CONSTANT_InterfaceMethodref:
    {
      _Jv_ushort class_index, name_and_type_index;
      _Jv_loadIndexes (&pool->data[index],
		       class_index,
		       name_and_type_index);
      jclass owner = (_Jv_ResolvePoolEntry (klass, class_index)).clazz;

      if (owner != klass)
	_Jv_InitClass (owner);

      _Jv_ushort name_index, type_index;
      _Jv_loadIndexes (&pool->data[name_and_type_index],
		       name_index,
		       type_index);

      _Jv_Utf8Const *method_name = pool->data[name_index].utf8;
      _Jv_Utf8Const *method_signature = pool->data[type_index].utf8;

      int vtable_index = -1;
      _Jv_Method *the_method = 0;
      jclass found_class = 0;

      // we make a loop here, because methods are allowed to be moved to
      // a super class, and still be visible.. (binary compatibility).

      for (jclass cls = owner; cls != 0; cls = cls->getSuperclass ())
	{
	  for (int i = 0;  i < cls->method_count;  i++)
	    {
	      _Jv_Method *method = &cls->methods[i];
	      if (   (!_Jv_equalUtf8Consts (method->name,
					    method_name))
		  || (!_Jv_equalUtf8Consts (method->signature,
					    method_signature)))
		continue;

	      if (cls == klass 
		  || ((method->accflags & PUBLIC) != 0)
		  || (((method->accflags & PROTECTED) != 0)
		      && cls->isAssignableFrom (klass))
		  || (((method->accflags & PRIVATE) == 0)
		      && _Jv_ClassNameSamePackage (cls->name,
						   klass->name)))
		{
		  // FIXME: if (cls->loader != klass->loader), then we
		  // must actually check that the types of arguments
		  // correspond.  That is, for each argument type, and
		  // the return type, doing _Jv_FindClassFromSignature
		  // with either loader should produce the same result,
		  // i.e., exactly the same jclass object. JVMS 5.4.3.3

		  the_method = method;
		  found_class = cls;

		  
		  if (pool->tags[index] == JV_CONSTANT_InterfaceMethodref)
		    vtable_index = -1;
		  else
		    vtable_index = _Jv_DetermineVTableIndex
		      (cls, method_name, method_signature);

		  if (vtable_index == 0)
		    throw_incompatible_class_change_error
		      (JvNewStringLatin1 ("method not found"));

		  goto end_of_method_search;
		}
	      else
		{
		  JvThrow (new java::lang::IllegalAccessError);
		}
	    }
	}

    end_of_method_search:
      if (the_method == 0)
	{
	  jstring msg = JvNewStringLatin1 ("method ");
	  msg = msg->concat (owner->getName ());
	  msg = msg->concat (JvNewStringLatin1("."));
	  msg = msg->concat (_Jv_NewStringUTF (method_name->data));
	  msg = msg->concat (JvNewStringLatin1(" was not found."));
	  JvThrow(new java::lang::NoSuchFieldError (msg));
	}
      
      pool->data[index].rmethod = 
	_Jv_BuildResolvedMethod(the_method,
				found_class,
				((the_method->accflags & STATIC) != 0),
				vtable_index);
      pool->tags[index] |= JV_CONSTANT_ResolvedFlag;
    }
    break;

  }

  return pool->data[index];
}


void
_Jv_ResolveField (_Jv_Field *field, java::lang::ClassLoader *loader)
{
  if (! field->isResolved ())
    {
      _Jv_Utf8Const *sig = (_Jv_Utf8Const*)field->type;
      field->type = _Jv_FindClassFromSignature (sig->data, loader);
      field->flags &= ~_Jv_FIELD_UNRESOLVED_FLAG;
    }
}

_Jv_Method*
_Jv_LookupDeclaredMethod (jclass klass, _Jv_Utf8Const *name,
			_Jv_Utf8Const *signature)
{
  for (; klass; klass = klass->getSuperclass())
    {
      _Jv_Method *meth = _Jv_GetMethodLocal (klass, name, signature);

      if (meth)
	return meth;
    }

  return NULL;
}

/** FIXME: this is a terribly inefficient algorithm!  It would improve
    things if compiled classes to know vtable offset, and _Jv_Method had
    a field for this.

    Returns 0  if this class does not declare the given method.
    Returns -1 if the given method does not appear in the vtable.
               i.e., it is static, private, final or a constructor.
    Otherwise, returns the vtable index.  */
int 
_Jv_DetermineVTableIndex (jclass klass,
			  _Jv_Utf8Const *name,
			  _Jv_Utf8Const *signature)
{
  jclass super_class = klass->getSuperclass ();

  if (super_class != NULL)
    {
      int prev = _Jv_DetermineVTableIndex (super_class,
					   name,
					   signature);
      if (prev != 0)
	return prev;
    }

  /* at this point, we know that the super-class does not declare
   * the method.  Otherwise, the above call would have found it, and
   * determined the result of this function (-1 or some positive
   * number).
   */

  _Jv_Method *meth = _Jv_GetMethodLocal (klass, name, signature);

  /* now, if we do not declare this method, return zero */
  if (meth == NULL)
    return 0;

  /* so now, we know not only that the super class does not declare the
   * method, but we do!  So, this is a first declaration of the method. */

  /* now, the checks for things that are declared in this class, but do
   * not go into the vtable.  There are three cases.  
   * 1) the method is static, private or final
   * 2) the class itself is final, or
   * 3) it is the method <init>
   */

  if (   (meth->accflags & (STATIC|PRIVATE|FINAL)) != 0
      || (klass->accflags & FINAL) != 0
      || _Jv_equalUtf8Consts (name, init_name))
    return -1;

  /* reaching this point, we know for sure, that the method in question
   * will be in the vtable.  The question is where. */

  /* the base offset, is where we will start assigning vtable
   * indexes for this class.  It is 1 for base classes
   * (vtable->method[0] is unused), and for non-base classes it is the
   * number of entries in the super class' vtable plus 1. */

  int base_offset;
  if (super_class == 0)
    base_offset = 1;
  else
    base_offset = super_class->vtable_method_count+1;

  /* we will consider methods 0..this_method_index-1.  And for each one,
   * determine if it is new (i.e., if it appears in the super class),
   * and if it should go in the vtable.  If so, increment base_offset */

  int this_method_index = meth - (&klass->methods[0]);

  for (int i = 0; i < this_method_index; i++)
    {
      _Jv_Method *m = &klass->methods[i];

      /* fist some checks for things that surely do not go in the
       * vtable */

      if ((m->accflags & (STATIC|PRIVATE)) != 0)
	continue;
      if (_Jv_equalUtf8Consts (m->name, init_name))
	continue;
      
      /* Then, we need to know if this method appears in the
         superclass. (This is where this function gets expensive) */
      _Jv_Method *sm = _Jv_LookupDeclaredMethod (super_class,
						 m->name,
						 m->signature);
      
      /* if it was somehow declared in the superclass, skip this */
      if (sm != NULL)
	continue;

      /* but if it is final, and not declared in the super class,
       * then we also skip it */
      if ((m->accflags & FINAL) != 0)
	continue;

      /* finally, we can assign the index of this method */
      /* m->vtable_index = base_offset */
      base_offset += 1;
    }

  return base_offset;
}

/* this is installed in place of abstract methods */
static void
_Jv_abstractMethodError ()
{
  JvThrow (new java::lang::AbstractMethodError);
}

void 
_Jv_PrepareClass(jclass klass)
{
 /*
  * The job of this function is to: 1) assign storage to fields, and 2)
  * build the vtable.  static fields are assigned real memory, instance
  * fields are assigned offsets.
  *
  * NOTE: we have a contract with the garbage collector here.  Static
  * reference fields must not be resolved, until after they have storage
  * assigned which is the check used by the collector to see if it
  * should indirect the static field reference and mark the object
  * pointed to. 
  *
  * Most fields are resolved lazily (i.e. have their class-type
  * assigned) when they are accessed the first time by calling as part
  * of _Jv_ResolveField, which is allways called after _Jv_PrepareClass.
  * Static fields with initializers are resolved as part of this
  * function, as are fields with primitive types.
  */

  if (! _Jv_IsInterpretedClass (klass))
    return;

  if (klass->state >= JV_STATE_PREPARED)
    return;

  // make sure super-class is linked.  This involves taking a lock on
  // the super class, so we use the Java method resolveClass, which will
  // unlock it properly, should an exception happen.

  java::lang::ClassLoader::resolveClass0 (klass->superclass);

  _Jv_InterpClass *clz = (_Jv_InterpClass*)klass;

  /************ PART ONE: OBJECT LAYOUT ***************/

  int instance_size;
  int static_size;

  // java.lang.Object is never interpreted!
  instance_size = clz->superclass->size ();
  static_size   = 0;

  for (int i = 0; i < clz->field_count; i++)
    {
      int field_size;
      int field_align;

      _Jv_Field *field = &clz->fields[i];

      if (! field->isRef ())
	{
	  // it's safe to resolve the field here, since it's 
	  // a primitive class, which does not cause loading to happen.
	  _Jv_ResolveField (field, clz->loader);

	  field_size = field->type->size ();
	  field_align = get_alignment_from_class (field->type);
	}
      else 
	{
	  field_size = sizeof (jobject);
	  field_align = __alignof__ (jobject);
	}

#ifndef COMPACT_FIELDS
      field->bsize = field_size;
#endif

      if (field->flags & STATIC)
	{
	  /* this computes an offset into a region we'll allocate 
	     shortly, and then add this offset to the start address */

	  static_size        = ROUND (static_size, field_align);
	  field->u.boffset   = static_size;
	  static_size       += field_size;
	}
      else
	{
	  instance_size      = ROUND (instance_size, field_align);
	  field->u.boffset   = instance_size;
	  instance_size     += field_size;
	}
    }

  // set the instance size for the class
  clz->size_in_bytes = instance_size;
    
  // allocate static memory
  if (static_size != 0)
    {
      char *static_data = (char*)_Jv_AllocBytesChecked (static_size);

      memset (static_data, 0, static_size);

      for (int i = 0; i < clz->field_count; i++)
	{
	  _Jv_Field *field = &clz->fields[i];

	  if ((field->flags & STATIC) != 0)
	    {
	      field->u.addr  = static_data + field->u.boffset;
			    
	      if (clz->field_initializers[i] != 0)
		{
		  _Jv_ResolveField (field, clz->loader);
		  _Jv_InitField (0, clz, i);
		}
	    }
	}

      // now we don't need the field_initializers anymore, so let the
      // collector get rid of it!

      clz->field_initializers = 0;
    }

  /************ PART TWO: VTABLE LAYOUT ***************/

  /* preparation: build the vtable stubs (even interfaces can)
     have code -- for static constructors. */
  for (int i = 0; i < clz->method_count; i++)
    {
      _Jv_InterpMethod *imeth = clz->interpreted_methods[i];

      if (imeth != 0)		// it could be abstract or native
	{
	  clz->methods[i].ncode = imeth->ncode ();
	}
      else
	{
	  if ((clz->methods[i].accflags & NATIVE) != 0)
	    {
	      JvThrow
		(new java::lang::VirtualMachineError
		 (JvNewStringLatin1 
		  ("the interpreter does not support native methods")));
	    }
	}
    }

  if (clz->accflags & INTERFACE)
    {
      clz->state = JV_STATE_PREPARED;
      clz->notifyAll ();
      return;
    }

  /* FIXME: native methods for interpreted classes should be handled, I
   * dunno exactly how, but it seems that we should try to find them at
   * this point, and if we fail, try again after <clinit>, since it
   * could have caused additional code to be loaded.  Interfaces cannot
   * have native methods (not even for static initialization). */


  /* Now onto the actual job: vtable layout.  First, count how many new
     methods we have */
  int new_method_count = 0;

  jclass super_class = clz->getSuperclass ();

  if (super_class == 0)
    throw_internal_error ("cannot handle interpreted base classes");

  for (int i = 0; i < clz->method_count; i++)
    {
      _Jv_Method *this_meth = &clz->methods[i];

      if ((this_meth->accflags & (STATIC|PRIVATE)) != 0
	  || _Jv_equalUtf8Consts (this_meth->name, init_name))
	{
	  /* skip this, it doesn't go in the vtable */
	  continue;
	}
	  
      _Jv_Method *orig_meth = _Jv_LookupDeclaredMethod (super_class,
							this_meth->name,
							this_meth->signature);

      if (orig_meth == 0)
	{
	  // new methods that are final, also don't go in the vtable
	  if ((this_meth->accflags & FINAL) != 0)
	    continue;

	  new_method_count += 1;
	  continue;
	}

      if ((orig_meth->accflags & (STATIC|PRIVATE|FINAL)) != 0
	  || ((orig_meth->accflags & ABSTRACT) == 0
	      && (this_meth->accflags & ABSTRACT) != 0
	      && (klass->accflags & ABSTRACT) == 0))
	{
	  clz->state = JV_STATE_ERROR;
	  clz->notifyAll ();
	  JvThrow (new java::lang::IncompatibleClassChangeError 
		           (clz->getName ()));
	}

      /* FIXME: At this point, if (loader != super_class->loader), we
       * need to "impose class loader constraints" for the types
       * involved in the signature of this method */
    }
  
  /* determine size */
  int vtable_count = (super_class->vtable_method_count) + new_method_count;
  clz->vtable_method_count = vtable_count;

  /* allocate vtable structure */
  _Jv_VTable *vtable = (_Jv_VTable*) 
    _Jv_AllocBytesChecked (sizeof (_Jv_VTable) 
			   + (sizeof (void*) * (vtable_count)));
  vtable->clas = clz;

  /* copy super class' vtable entries (index 0 goes unused). */
  memcpy ((void*)&vtable->method[1],
	  (void*)&super_class->vtable->method[1],
	  sizeof (void*) * super_class->vtable_method_count);

  /* now, install our own vtable entries, reprise... */
  for (int i = 0; i < clz->method_count; i++)
    {
      _Jv_Method *this_meth = &clz->methods[i];

      int index = _Jv_DetermineVTableIndex (clz, 
					    this_meth->name,
					    this_meth->signature);

      if (index == 0)
	throw_internal_error ("method now found in own class");

      if (index != -1)
	{
	  if (index > clz->vtable_method_count+1)
	    throw_internal_error ("vtable problem...");

	  if (clz->interpreted_methods[i] == 0)
	    vtable->method[index] = (void*)&_Jv_abstractMethodError;
	  else
	    vtable->method[index] = this_meth->ncode;
	}
    }

  /* finally, assign the vtable! */
  clz->vtable = vtable;

  /* wooha! we're done. */
  clz->state = JV_STATE_PREPARED;
  clz->notifyAll ();
}

/** Do static initialization for fields with a constant initializer */
void
_Jv_InitField (jobject obj, jclass klass, int index)
{
  if (obj != 0 && klass == 0)
    klass = obj->getClass ();

  if (!_Jv_IsInterpretedClass (klass))
    return;

  _Jv_InterpClass *clz = (_Jv_InterpClass*)klass;

  _Jv_Field * field = (&clz->fields[0]) + index;

  if (index > clz->field_count)
    throw_internal_error ("field out of range");

  int init = clz->field_initializers[index];
  if (init == 0)
    return;

  _Jv_Constants *pool = &clz->constants;
  int tag = pool->tags[init];

  if (! field->isResolved ())
    throw_internal_error ("initializing unresolved field");

  if (obj==0 && ((field->flags & STATIC) == 0))
    throw_internal_error ("initializing non-static field with no object");

  void *addr = 0;

  if ((field->flags & STATIC) != 0)
    addr = (void*) field->u.addr;
  else
    addr = (void*) (((char*)obj) + field->u.boffset);

  switch (tag)
    {
    case JV_CONSTANT_String:
      {
	_Jv_MonitorEnter (clz);
	jstring str;
	str = _Jv_NewStringUtf8Const (pool->data[init].utf8);
	pool->data[init].string = str;
	pool->tags[init] = JV_CONSTANT_ResolvedString;
	_Jv_MonitorExit (clz);
      }
      /* fall through */

    case JV_CONSTANT_ResolvedString:
      if (! (field->type == &StringClass || field->type == &ObjectClass))
	throw_class_format_error ("string initialiser to non-string field");

      *(jstring*)addr = pool->data[init].string;
      break;

    case JV_CONSTANT_Integer:
      {
	int value = pool->data[init].i;

	if (field->type == JvPrimClass (boolean))
	  *(jboolean*)addr = (jboolean)value;
	
	else if (field->type == JvPrimClass (byte))
	  *(jbyte*)addr = (jbyte)value;
	
	else if (field->type == JvPrimClass (char))
	  *(jchar*)addr = (jchar)value;

	else if (field->type == JvPrimClass (short))
	  *(jshort*)addr = (jshort)value;
	
	else if (field->type == JvPrimClass (int))
	  *(jint*)addr = (jint)value;

	else
	  throw_class_format_error ("erroneous field initializer");
      }  
      break;

    case JV_CONSTANT_Long:
      if (field->type != JvPrimClass (long))
	throw_class_format_error ("erroneous field initializer");

      *(jlong*)addr = _Jv_loadLong (&pool->data[init]);
      break;

    case JV_CONSTANT_Float:
      if (field->type != JvPrimClass (float))
	throw_class_format_error ("erroneous field initializer");

      *(jfloat*)addr = pool->data[init].f;
      break;

    case JV_CONSTANT_Double:
      if (field->type != JvPrimClass (double))
	throw_class_format_error ("erroneous field initializer");

      *(jdouble*)addr = _Jv_loadDouble (&pool->data[init]);
      break;

    default:
      throw_class_format_error ("erroneous field initializer");
    }
}

static int
get_alignment_from_class (jclass klass)
{
  if (klass == JvPrimClass (byte))
    return  __alignof__ (jbyte);
  else if (klass == JvPrimClass (short))
    return  __alignof__ (jshort);
  else if (klass == JvPrimClass (int)) 
    return  __alignof__ (jint);
  else if (klass == JvPrimClass (long))
    return  __alignof__ (jlong);
  else if (klass == JvPrimClass (boolean))
    return  __alignof__ (jboolean);
  else if (klass == JvPrimClass (char))
    return  __alignof__ (jchar);
  else if (klass == JvPrimClass (float))
    return  __alignof__ (jfloat);
  else if (klass == JvPrimClass (double))
    return  __alignof__ (jdouble);
  else
    return __alignof__ (jobject);
}


inline static unsigned char*
skip_one_type (unsigned char* ptr)
{
  int ch = *ptr++;

  while (ch == '[')
    { 
      ch = *ptr++;
    }
  
  if (ch == 'L')
    {
      do { ch = *ptr++; } while (ch != ';');
    }

  return ptr;
}

static ffi_type*
get_ffi_type_from_signature (unsigned char* ptr)
{
  switch (*ptr) 
    {
    case 'L':
    case '[':
      return &ffi_type_pointer;
      break;

    case 'Z':
    case 'B':
      return &ffi_type_sint8;
      break;
      
    case 'C':
      return &ffi_type_uint16;
      break;
	  
    case 'S': 
      return &ffi_type_sint16;
      break;
	  
    case 'I':
      return &ffi_type_sint32;
      break;
	  
    case 'J':
      return &ffi_type_sint64;
      break;
	  
    case 'F':
      return &ffi_type_float;
      break;
	  
    case 'D':
      return &ffi_type_double;
      break;

    case 'V':
      return &ffi_type_void;
      break;
    }

  throw_internal_error ("unknown type in signature");
}

/* this function yields the number of actual arguments, that is, if the
 * function is non-static, then one is added to the number of elements
 * found in the signature */

static int 
count_arguments (_Jv_Utf8Const *signature,
		 jboolean staticp)
{
  unsigned char *ptr = (unsigned char*) signature->data;
  int arg_count = staticp ? 0 : 1;

  /* first, count number of arguments */

  // skip '('
  ptr++;

  // count args
  while (*ptr != ')')
    {
      ptr = skip_one_type (ptr);
      arg_count += 1;
    }

  return arg_count;
}

/* This beast will build a cif, given the signature.  Memory for
 * the cif itself and for the argument types must be allocated by the
 * caller.
 */

static int 
init_cif (_Jv_Utf8Const* signature,
	  int arg_count,
	  jboolean staticp,
	  ffi_cif *cif,
	  ffi_type **arg_types)
{
  unsigned char *ptr = (unsigned char*) signature->data;

  int arg_index = 0;		// arg number
  int item_count = 0;		// stack-item count

  // setup receiver
  if (!staticp)
    {
      arg_types[arg_index++] = &ffi_type_pointer;
      item_count += 1;
    }

  // skip '('
  ptr++;

  // assign arg types
  while (*ptr != ')')
    {
      arg_types[arg_index++] = get_ffi_type_from_signature (ptr);

      if (*ptr == 'J' || *ptr == 'D')
	item_count += 2;
      else
	item_count += 1;

      ptr = skip_one_type (ptr);
    }

  // skip ')'
  ptr++;
  ffi_type *rtype = get_ffi_type_from_signature (ptr);

  ptr = skip_one_type (ptr);
  if (ptr != (unsigned char*)signature->data + signature->length)
    throw_internal_error ("did not find end of signature");

  if (ffi_prep_cif (cif, FFI_DEFAULT_ABI,
		    arg_count, rtype, arg_types) != FFI_OK)
    throw_internal_error ("ffi_prep_cif failed");

  return item_count;
}


/* we put this one here, and not in interpret.cc because it
 * calls the utility routines count_arguments 
 * which are static to this module.  The following struct defines the
 * layout we use for the stubs, it's only used in the ncode method. */

typedef struct {
  ffi_raw_closure  closure;
  ffi_cif   cif;
  ffi_type *arg_types[0];
} ncode_closure;

typedef void (*ffi_closure_fun) (ffi_cif*,void*,ffi_raw*,void*);

void* _Jv_InterpMethod::ncode ()
{
  if (self->ncode != 0)
    return self->ncode;

  jboolean staticp = (self->accflags & STATIC) != 0;
  int arg_count = count_arguments (self->signature, staticp);

  ncode_closure *closure =
    (ncode_closure*)_Jv_AllocBytesChecked (sizeof (ncode_closure)
					+ arg_count * sizeof (ffi_type*));

  init_cif (self->signature,
	    arg_count,
	    staticp,
	    &closure->cif,
	    &closure->arg_types[0]);

  ffi_closure_fun fun;

  args_raw_size = ffi_raw_size (&closure->cif);

  if ((self->accflags & SYNCHRONIZED) != 0)
    {
      if (staticp)
	fun = (ffi_closure_fun)&_Jv_InterpMethod::run_synch_class;
      else
	fun = (ffi_closure_fun)&_Jv_InterpMethod::run_synch_object; 
    }
  else
    {
      fun = (ffi_closure_fun)&_Jv_InterpMethod::run_normal;
    }

  ffi_prep_raw_closure (&closure->closure,
		     &closure->cif, 
		     fun,
		     (void*)this);

  self->ncode = (void*)closure;
  return self->ncode;
}


/* A _Jv_ResolvedMethod is what is put in the constant pool for a
 * MethodRef or InterfacemethodRef.  */
static _Jv_ResolvedMethod*
_Jv_BuildResolvedMethod (_Jv_Method* method,
			 jclass      klass,
			 jboolean staticp,
			 jint vtable_index)
{
  int arg_count = count_arguments (method->signature, staticp);

  _Jv_ResolvedMethod* result = (_Jv_ResolvedMethod*)
    _Jv_AllocBytesChecked (sizeof (_Jv_ResolvedMethod)
			   + arg_count*sizeof (ffi_type*));

  result->stack_item_count
    = init_cif (method->signature,
		arg_count,
		staticp,
		&result->cif,
		&result->arg_types[0]);

  result->vtable_index        = vtable_index;
  result->method              = method;
  result->klass               = klass;

  return result;
}


static void
throw_class_format_error (jstring msg)
{
  if (msg == 0)
    JvThrow (new java::lang::ClassFormatError);
  else
    JvThrow (new java::lang::ClassFormatError (msg));
}

static void
throw_class_format_error (char *msg)
{
  throw_class_format_error (JvNewStringLatin1 (msg));
}

static void
throw_internal_error (char *msg)
{
  JvThrow 
    (new java::lang::InternalError (JvNewStringLatin1 (msg)));
}


#endif