exception.cc

// Functions for Exception Support for Java.

/* Copyright (C) 1998, 1999  Free Software Foundation

   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.  */

#include <config.h>

#include <stddef.h>
#include <stdlib.h>

#include <java/lang/Class.h>
#include <java/lang/NullPointerException.h>
#include <gcj/cni.h>
#include <jvm.h>

// eh-common.h needs gansidecl.h.
#include "gansidecl.h"
#include "eh-common.h"

typedef struct {
  __eh_info eh_info;
  void *value;
} java_eh_info;


/* Language-specific EH info pointer, throw routine, and language/version
   info routines. All defined in libgcc2. */

extern "C" java_eh_info **__get_eh_info (); 
extern "C" void __throw () __attribute__ ((__noreturn__));
extern "C" void __sjthrow () __attribute__ ((__noreturn__));
extern "C" short __get_eh_table_version (void *table);
extern "C" short __get_eh_table_language (void *table);
extern "C" void *__get_eh_context ();

extern "C" void *
_Jv_type_matcher (java_eh_info *info, void* match_info, 
		  void *exception_table)
{
#ifndef SJLJ_EXCEPTIONS
  /* No exception table implies the old style mechanism, so don't check. */
  if (exception_table != NULL
      && __get_eh_table_language (exception_table) != EH_LANG_Java)
    return NULL;
#endif

  /* we don't worry about version info yet, there is only one version! */
  
  if (match_info != NULL)
    {
      // The match_info is either a (java::lang::Class*) or
      // match_info is one more than a (Utf8Const*).
      if (sizeof(void*) != sizeof(size_t))
	abort();
      size_t mi = (size_t) match_info;
      if ((mi & 1) != 0)
	match_info = _Jv_FindClass ((Utf8Const*) (mi - 1), NULL);
      if (! _Jv_IsInstanceOf ((jobject) info->value, (jclass) match_info))
	return NULL;
    }

  return info->value;
}

/* Compiler hook to return a pointer to java exception object. The value
   is cleared, so if the exception needs to be rethrown, it should be set 
   again */

extern "C" void *
_Jv_exception_info (void)
{
  java_eh_info *info = *(__get_eh_info ());
  void *ptr;

  if (info == NULL)
    abort ();

  ptr = info->value;

  /* clear the value so another throw is an error */
  info->value = NULL;

  return ptr;
}



/* Allocate an exception info structure for java. Called the first time
   an exception is thrown. */

extern "C" void
_Jv_eh_alloc ()
{
  /* FIXME: we should use _Jv_AllocBytes here.  However, libgcc2
     apparently can sometimes free() this value itself.  */
  java_eh_info *p = (java_eh_info *) malloc (sizeof (java_eh_info));
  if (p == 0)
    abort ();

  p->value = 0;
  java_eh_info ** info_ptr = __get_eh_info ();

  /* There should NOT be an exception info pointer already. */
  if (*info_ptr != NULL)
    abort ();

  *info_ptr = p;
}

/* Deallocate the current exception info structure. Called at shutdown time. */

extern "C" void
_Jv_eh_free ()
{
  java_eh_info ** info_ptr = __get_eh_info ();
  if (*info_ptr == NULL)
    abort ();
  
  /* FIXME: ideally we should just let the GC handle this.  */
  free (*info_ptr);
  *info_ptr = NULL;
}

/* Initialize an __eh_info structure with this libraries matching info. */

extern "C" void
_Jv_setup_eh_info (__eh_info *)
{
}

/* Perform a throw, Java style. Throw will unwind through this call,
   so there better not be any handlers or exception thrown here. */

extern "C" void
_Jv_Throw (void *value)
{
  if (value == NULL)
    value = (void *) new java::lang::NullPointerException ();
  java_eh_info *ehinfo = *(__get_eh_info ());
  if (ehinfo == NULL)
    {
      _Jv_eh_alloc ();
      ehinfo = *(__get_eh_info ());
    }
  ehinfo->eh_info.match_function = (__eh_matcher) _Jv_type_matcher;
  ehinfo->eh_info.language = EH_LANG_Java;
  ehinfo->eh_info.version = 1;
  ehinfo->value = value;

/* We're happy with setjmp/longjmp exceptions or region-based
   exception handlers: entry points are provided here for both.  */
#ifdef SJLJ_EXCEPTIONS
  __sjthrow ();
#else
  __throw ();
#endif
}

#ifdef USE_WIN32_SIGNALLING

// This is a mangled version of _Jv_Throw and __sjthrow except
// rather than calling longjmp, it returns a pointer to the jmp buffer

extern "C" int *
win32_get_restart_frame (void *value)
{
  struct eh_context *eh = (struct eh_context *)__get_eh_context ();
  void ***dhc = &eh->dynamic_handler_chain;
 
  java_eh_info *ehinfo = *(__get_eh_info ());
  if (ehinfo == NULL)
    {
      _Jv_eh_alloc ();
      ehinfo = *(__get_eh_info ());
    }
  ehinfo->eh_info.match_function = (__eh_matcher) _Jv_type_matcher;
  ehinfo->eh_info.language = EH_LANG_Java;
  ehinfo->eh_info.version = 1;
  ehinfo->value = value;

  // FIXME: Run clean ups?

  int *jmpbuf = (int*)&(*dhc)[2];

  *dhc = (void**)(*dhc)[0];

  return  jmpbuf;
}

#endif /* USE_WIN32_SIGNALLING */