glibc/csu/initfini.c

/* Special .init and .fini section support.
Copyright (C) 1995, 1996 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 Library General Public License as
published by the Free Software Foundation; either version 2 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
Library General Public License for more details.

You should have received a copy of the GNU Library General Public
License along with the GNU C Library; see the file COPYING.LIB.  If
not, write to the Free Software Foundation, Inc., 675 Mass Ave,
Cambridge, MA 02139, USA.  */

/* This file is compiled into assembly code which is then surrounded by the
   lines `cat > crtcommon.tmp <<\EOF_common' and `EOF_common' and thus
   becomes a shell script which creates three files of assembly code.

   * The first file is crti.s-new; this 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.

   * The second file is crtn.s-new; this puts the corresponding function
   epilogues in the .init and .fini sections.

   * The third file is crtcommon.tmp, which is whatever miscellaneous cruft
   the compiler generated at the end; it should be appended to both crti.s-new
   and crtn.s-new.  */

#include <stdlib.h>


#ifdef HAVE_ELF
/* These declarations make the functions go in the right sections when
   we define them below.  GCC syntax does not allow the attribute
   specifications to be in the function definitions themselves.  */
void _init (void) __attribute__ ((section (".init")));
void _fini (void) __attribute__ ((section (".fini")));

#define SECTION(x)		/* Put nothing extra before the defn.  */

#else
/* Some non-ELF systems support .init and .fini sections,
   but the __attribute__ syntax only works for ELF.  */
#define SECTION(x) asm (".section " x);
#endif

/* End the here document containing the initial common code.
   Then move the output file crtcommon.tmp to crti.s-new and crtn.s-new.  */
asm ("\nEOF_common\n\
rm -f crti.s-new crtn.s-new\n\
mv crtcommon.tmp crti.s-new\n\
cp crti.s-new crtn.s-new");

/* Extract a `.end' if one is produced by the compiler.  */
asm ("fgrep .end >/dev/null 2>&1 <<\\EOF.end && need_end=yes");
void
useless_function (void)
{
  return;
}
asm ("\nEOF.end\n");

/* Find out how much alignment is produced by the compiler.  */
asm ("align=`awk '$1==\".align\" { if ($2>max) max=$2; } END { print max; }' \
<<\\EOF.align");
void
useless_function2 (void (*foo) (void))
{
  if (foo)
    (*foo) ();
}
asm ("\nEOF.align\n`\n");

/* Append the .init prologue to crti.s-new.  */
asm ("cat >> crti.s-new <<\\EOF.crti.init");

SECTION (".init")
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.  */
  extern void __gmon_start__ (void); weak_extern (__gmon_start__)
  if (__gmon_start__)
    __gmon_start__ ();

  /* End the here document containing the .init prologue code.
     Then fetch the .section directive just written and append that
     to crtn.s-new, followed by the function epilogue.  */
  asm ("\n\
EOF.crti.init\n\
	test -n \"$align\" && echo .align $align >> crti.s-new\n\
	test -n \"$need_end\" && echo .end _init >> crti.s-new\n\
	fgrep .init crti.s-new >>crtn.s-new\n\
	fgrep -v .end >> crtn.s-new <<\\EOF.crtn.init");
}

/* End the here document containing the .init epilogue code.
   Then append the .fini prologue to crti.s-new.  */
asm ("\nEOF.crtn.init\
\n\
cat >> crti.s-new <<\\EOF.crti.fini");

SECTION (".fini")
void
_fini (void)
{
  /* End the here document containing the .fini prologue code.
     Then fetch the .section directive just written and append that
     to crtn.s-new, followed by the function epilogue.  */
  asm ("\nEOF.crti.fini\n\
test -n \"$align\" && echo .align $align >> crti.s-new\n\
test -n \"$need_end\" && echo .end _fini >> crti.s-new\n\
cat > /dev/null <<\\EOF.fini.skip");

  {
    /* 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 ();
  }

  asm ("\nEOF.fini.skip\
\n\
	fgrep .fini crti.s-new >>crtn.s-new\n\
	fgrep -v .end >> crtn.s-new <<\\EOF.crtn.fini");
}

/* End the here document containing the .fini epilogue code.
   Finally, put the remainder of the generated assembly into crtcommon.tmp.  */
asm ("\nEOF.crtn.fini\
\n\
cat > crtcommon.tmp <<\\EOF_common");