ptx4-i.h

gcc-you can use this code to learn something about gcc, and inquire further into linux,

/* Target definitions for GNU compiler for Intel 80386 running Dynix/ptx v4
   Copyright (C) 1996, 2002 Free Software Foundation, Inc.

   Modified from sysv4.h
   Originally written by Ron Guilmette ([e-mail]).
   Modified by Tim Wright ([e-mail]).

This file is part of GNU CC.

GNU CC is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2, or (at your option)
any later version.

GNU CC is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with GNU CC; see the file COPYING.  If not, write to
the Free Software Foundation, 59 Temple Place - Suite 330,
Boston, MA 02111-1307, USA.  */


#define TARGET_VERSION fprintf (stderr, " (i386 Sequent Dynix/ptx Version 4)");

/* The svr4 ABI for the i386 says that records and unions are returned
   in memory.  */

#undef RETURN_IN_MEMORY
#define RETURN_IN_MEMORY(TYPE) \
  (TYPE_MODE (TYPE) == BLKmode \
   || (VECTOR_MODE_P (TYPE_MODE (TYPE)) && int_size_in_bytes (TYPE) == 8))

#define TARGET_OS_CPP_BUILTINS()		\
  do						\
    {						\
	builtin_define_std ("unix");		\
	builtin_define ("_SEQUENT_");		\
	builtin_assert ("system=unix");		\
	builtin_assert ("system=ptx4");		\
    }						\
  while (0)

#undef DBX_REGISTER_NUMBER
#define DBX_REGISTER_NUMBER(n)  svr4_dbx_register_map[n]

/* The routine used to output sequences of byte values.  We use a special
   version of this for most svr4 targets because doing so makes the
   generated assembly code more compact (and thus faster to assemble)
   as well as more readable.  Note that if we find subparts of the
   character sequence which end with NUL (and which are shorter than
   STRING_LIMIT) we output those using ASM_OUTPUT_LIMITED_STRING.  */

#undef ASM_OUTPUT_ASCII
#define ASM_OUTPUT_ASCII(FILE, STR, LENGTH)				\
  do									\
    {									\
      register const unsigned char *_ascii_bytes =			\
        (const unsigned char *) (STR);					\
      register const unsigned char *limit = _ascii_bytes + (LENGTH);	\
      register unsigned bytes_in_chunk = 0;				\
      for (; _ascii_bytes < limit; _ascii_bytes++)			\
        {								\
	  register const unsigned char *p;				\
	  if (bytes_in_chunk >= 64)					\
	    {								\
	      fputc ('\n', (FILE));					\
	      bytes_in_chunk = 0;					\
	    }								\
	  for (p = _ascii_bytes; p < limit && *p != '\0'; p++)		\
	    continue;							\
	  if (p < limit && (p - _ascii_bytes) <= (long) STRING_LIMIT)	\
	    {								\
	      if (bytes_in_chunk > 0)					\
		{							\
		  fputc ('\n', (FILE));					\
		  bytes_in_chunk = 0;					\
		}							\
	      ASM_OUTPUT_LIMITED_STRING ((FILE), _ascii_bytes);		\
	      _ascii_bytes = p;						\
	    }								\
	  else								\
	    {								\
	      if (bytes_in_chunk == 0)					\
		fprintf ((FILE), "\t.byte\t");				\
	      else							\
		fputc (',', (FILE));					\
	      fprintf ((FILE), "0x%02x", *_ascii_bytes);		\
	      bytes_in_chunk += 5;					\
	    }								\
	}								\
      if (bytes_in_chunk > 0)						\
        fprintf ((FILE), "\n");						\
    }									\
  while (0)