csu/gmon-start.c

   1 /* Code to enable profiling at program startup.
   2    Copyright (C) 1995, 1996, 1997, 2000 Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   4
   5    The GNU C Library is free software; you can redistribute it and/or
   6    modify it under the terms of the GNU Library General Public License as
   7    published by the Free Software Foundation; either version 2 of the
   8    License, or (at your option) any later version.
   9
  10    The GNU C Library is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13    Library General Public License for more details.
  14
  15    You should have received a copy of the GNU Library General Public
  16    License along with the GNU C Library; see the file COPYING.LIB.  If not,
  17    write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
  18    Boston, MA 02111-1307, USA.  */
  19
  20 #include <sys/types.h>
  21 #include <sys/gmon.h>
  22 #include <stdlib.h>
  23 #include <unistd.h>
  24
  25 /* Beginning and end of our code segment. We cannot declare them
  26    as the external functions since we want the addresses of those
  27    labels. Taking the address of a function may have different
  28    meanings on different platforms. */
  29 extern void _start, etext;
  30
  31 #ifndef HAVE_INITFINI
  32 /* This function gets called at startup by the normal constructor
  33    mechanism.  We link this file together with start.o to produce gcrt1.o,
  34    so this constructor will be first in the list.  */
  35
  36 extern void __gmon_start__ (void) __attribute__ ((constructor));
  37 #else
  38 /* In ELF and COFF, we cannot use the normal constructor mechanism to call
  39    __gmon_start__ because gcrt1.o appears before crtbegin.o in the link.
  40    Instead crti.o calls it specially (see initfini.c).  */
  41 extern void __gmon_start__ (void);
  42 #endif
  43
  44 void
  45 __gmon_start__ (void)
  46 {
  47 #ifdef HAVE_INITFINI
  48   /* Protect from being called more than once.  Since crti.o is linked
  49      into every shared library, each of their init functions will call us.  */
  50   static int called;
  51
  52   if (called)
  53     return;
  54
  55   called = 1;
  56 #endif
  57
  58   /* Start keeping profiling records.  */
  59   __monstartup ((u_long) &_start, (u_long) &etext);
  60
  61   /* Call _mcleanup before exiting; it will write out gmon.out from the
  62      collected data.  */
  63   atexit (&_mcleanup);
  64 }