glibc/sysdeps/generic/initfini.c

/* 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.

   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 <stdlib.h>

/* 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 )

/* Embed an #include to pull in the alignment and .end directives. */
asm ("\n#include \"defs.h\"");

/* 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*/");

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 ();
}

SECTION (".init");
extern void _init (void);
void
_init (void)
{
  /* 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 ();

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

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

SECTION (".fini");
extern void _fini (void);
void
_fini (void)
{

  /* End of the _fini prolog. */
  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.  */
    extern void i_am_not_a_leaf (void);
    i_am_not_a_leaf ();
  }

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

/* 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. */