initfini.c

它通过提供glibc兼容使得应用程序移植到较小的c 库时相当得容易. 它能够应用到带虚拟存储的Linux和uClinux上.在大多数带MMU部件的平台上为使它更加紧凑,它也能够编译成共享库.uClib

/* Special .init and .fini section support.
   Copyright (C) 1995, 1996, 1997, 2000 Free Software Foundation, Inc.
   This file is part of the GNU C Library.

   The GNU C Library is free software; you can redistribute it and/or
   modify it under the terms of the GNU Lesser General Public
   License as published by the Free Software Foundation; either
   version 2.1 of the License, or (at your option) any later version.

   In addition to the permissions in the GNU Lesser General Public
   License, the Free Software Foundation gives you unlimited
   permission to link the compiled version of this file with other
   programs, and to distribute those programs without any restriction
   coming from the use of this file.  (The GNU Lesser General Public
   License restrictions do apply in other respects; for example, they
   cover modification of the file, and distribution when not linked
   into another program.)

   The GNU C Library 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
   Lesser General Public License for more details.

   You should have received a copy of the GNU Lesser General Public
   License along with the GNU C Library; if not, write to the Free
   Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
   02111-1307 USA.  */

/* This file is compiled into assembly code which is then munged by a sed
   script into two files: crti.s and crtn.s.

   * crti.s puts a function prologue at the beginning of the
   .init and .fini sections and defines global symbols for
   those addresses, so they can be called as functions.

   * crtn.s puts the corresponding function epilogues
   in the .init and .fini sections. */

#include <features.h>

#undef GMON_SUPPORT

/* We use embedded asm for .section unconditionally, as this makes it
   easier to insert the necessary directives into crtn.S. */
#define SECTION(x) asm (".section " x );

/* Declare symbols as hidden. Hidden symbols are only seen by
 * the link editor and not by the dynamic loader. */
#ifdef __HAVE_DOT_HIDDEN__
#  define HIDDEN(func)  asm (".hidden  " #func );
#else
#  define HIDDEN(func)
#endif

#if defined(__sh__)
  /* The macro insert this sh specific stuff:
     @_SH_GLB_BEGINS
          bra     1f
	  nop
	  ALIGN
     @func_SH_GLB_LABEL
     1:
     @_SH_GLB_ENDS
   */
#define GLB_STUFF(func)  asm ("\n/*@_SH_GLB_BEGINS*/"); \
  asm ("\n\tbra\t1f\n\tnop\n\tALIGN\n/*@" #func"_SH_GLB_LABEL*/\n1:"); \
  asm ("\n/*@_SH_GLB_ENDS*/");
#else
#define GLB_STUFF(func)
#endif

/* The initial common code ends here. */
asm ("\n/*@HEADER_ENDS*/");

/* To determine whether we need .end and .align: */
//asm ("\n/*@TESTS_BEGIN*/");
extern void dummy (void (*foo) (void));
void
dummy (void (*foo) (void))
{
  if (foo)
    (*foo) ();
}
//asm ("\n/*@TESTS_END*/");

/* The beginning of _init:  */
asm ("\n/*@_init_PROLOG_BEGINS*/");

#ifdef GMON_SUPPORT
static void
call_gmon_start(void)
{
  extern void __gmon_start__ (void) __attribute__ ((weak)); /*weak_extern (__gmon_start__);*/
  void (*gmon_start) (void) = __gmon_start__;

  if (gmon_start)
    gmon_start ();
}
#endif

SECTION (".init")
HIDDEN(_init)

extern void i_am_not_a_leaf (void);
extern void _init (void);
void _init (void)
{
#ifdef GMON_SUPPORT
  /* We cannot use the normal constructor mechanism in gcrt1.o because it
     appears before crtbegin.o in the link, so the header elt of .ctors
     would come after the elt for __gmon_start__.  One approach is for
     gcrt1.o to reference a symbol which would be defined by some library
     module which has a constructor; but then user code's constructors
     would come first, and not be profiled.  */
  call_gmon_start ();
#else
  asm ("\n/*@_init_PROLOG_PAUSES*/");
  {
    /* Let GCC know that _init is not a leaf function by having a dummy
     * function call here.  We arrange for this call to be omitted from
     * either crt file.  */
    i_am_not_a_leaf ();
  }
  asm ("\n/*@_init_PROLOG_UNPAUSES*/");
#endif

  GLB_STUFF(_init)
  asm ("ALIGN");
  asm("END_INIT");
  /* Now the epilog. */
  asm ("\n/*@_init_PROLOG_ENDS*/");
  asm ("\n/*@_init_EPILOG_BEGINS*/");
}

/* End of the _init epilog, beginning of the _fini prolog. */
asm ("\n/*@_init_EPILOG_ENDS*/");
asm ("\n/*@_fini_PROLOG_BEGINS*/");

SECTION (".fini")
HIDDEN(_fini)

extern void i_am_not_a_leaf2 (void);
extern void _fini (void);
void _fini (void)
{

  /* End of the _fini prolog. */
  GLB_STUFF(_fini)
  asm ("ALIGN");
  asm ("END_FINI");
  asm ("\n/*@_fini_PROLOG_ENDS*/");

  {
    /* Let GCC know that _fini is not a leaf function by having a dummy
       function call here.  We arrange for this call to be omitted from
       either crt file.  */
    i_am_not_a_leaf2 ();
  }

  /* Beginning of the _fini epilog. */
  asm ("\n/*@_fini_EPILOG_BEGINS*/");
}

/* End of the _fini epilog.  Any further generated assembly (e.g. .ident)
   is shared between both crt files. */
asm ("\n/*@_fini_EPILOG_ENDS*/");
asm ("\n/*@TRAILER_BEGINS*/");

/* End of file. */