osf5.h

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

/* Definitions of target machine for GNU compiler, for DEC Alpha on Tru64 5.
   Copyright (C) 2000, 2001 Free Software Foundation, Inc.

   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.  */

/* Tru64 5.1 uses IEEE QUAD format.  */
/* ??? However, since there is no support for VAX H_floating, we must
   drop back to a 64-bit long double to avoid a crash looking for the
   format associated with TFmode.  */
#undef LONG_DOUBLE_TYPE_SIZE
#define LONG_DOUBLE_TYPE_SIZE  (TARGET_FLOAT_VAX ? 64 : 128)

/* In Tru64 UNIX V5.1, Compaq introduced a new assembler
   (/usr/lib/cmplrs/cc/adu) which currently (versions between 3.04.29 and
   3.04.32) breaks mips-tfile.  Passing the undocumented -oldas flag reverts
   to using the old assembler (/usr/lib/cmplrs/cc/as[01]).

   The V5.0 and V5.0A assemblers silently ignore -oldas, so it can be
   specified here.

   It is clearly not desirable to depend on this undocumented flag, and
   Compaq wants -oldas to go away soon, but until they have released a
   new adu that works with mips-tfile, this is the only option.

   In some versions of the DTK, the assembler driver invokes ld after
   assembly.  This has been fixed in current versions, but adding -c
   works as expected for all versions.  */

#undef ASM_OLDAS_SPEC
#define ASM_OLDAS_SPEC "-oldas -c"

/* The linker appears to perform invalid code optimizations that result
   in the ldgp emitted for the exception_receiver pattern being incorrectly
   linked.  */
#undef TARGET_LD_BUGGY_LDGP
#define TARGET_LD_BUGGY_LDGP 1