csu/initfini.c

   1 /* Special .init and .fini section support.
   2    Copyright (C) 1995, 1996, 1997 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
   6    and/or modify it under the terms of the GNU Library General Public
   7    License as published by the Free Software Foundation; either
   8    version 2 of the License, or (at your option) any later version.
   9
  10    In addition to the permissions in the GNU Library General Public
  11    License, the Free Software Foundation gives you unlimited
  12    permission to link the compiled version of this file with other
  13    programs, and to distribute those programs without any restriction
  14    coming from the use of this file.  (The Library General Public
  15    License restrictions do apply in other respects; for example, they
  16    cover modification of the file, and distribution when not linked
  17    into another program.)
  18
  19    The GNU C Library is distributed in the hope that it will be
  20    useful, but WITHOUT ANY WARRANTY; without even the implied warranty
  21    of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  22    GNU Library General Public License for more details.
  23
  24    You should have received a copy of the GNU Library General Public
  25    License along with the GNU C Library; see the file COPYING.LIB.  If not,
  26    write to the Free Software Foundation, 59 Temple Place - Suite 330,
  27    Boston, MA 02111-1307, USA.  */
  28
  29 /* This file is compiled into assembly code which is then munged by a sed
  30    script into two files: crti.s and crtn.s.
  31
  32    * crti.s puts a function prologue at the beginning of the
  33    .init and .fini sections and defines global symbols for
  34    those addresses, so they can be called as functions.
  35
  36    * crtn.s puts the corresponding function epilogues
  37    in the .init and .fini sections. */
  38
  39 #include <stdlib.h>
  40
  41 /* We use embedded asm for .section unconditionally, as this makes it
  42    easier to insert the necessary directives into crtn.S. */
  43 #define SECTION(x) asm (".section " x );
  44
  45 /* Embed an #include to pull in the alignment and .end directives. */
  46 asm ("\n#include \"defs.h\"");
  47
  48 /* The initial common code ends here. */
  49 asm ("\n/*@HEADER_ENDS*/");
  50
  51 /* To determine whether we need .end and .align: */
  52 asm ("\n/*@TESTS_BEGIN*/");
  53 void
  54 dummy (void (*foo) (void))
  55 {
  56   if (foo)
  57     (*foo) ();
  58 }
  59 asm ("\n/*@TESTS_END*/");
  60
  61 /* The beginning of _init:  */
  62 asm ("\n/*@_init_PROLOG_BEGINS*/");
  63
  64 SECTION (".init")
  65 void
  66 _init (void)
  67 {
  68   /* We cannot use the normal constructor mechanism in gcrt1.o because it
  69      appears before crtbegin.o in the link, so the header elt of .ctors
  70      would come after the elt for __gmon_start__.  One approach is for
  71      gcrt1.o to reference a symbol which would be defined by some library
  72      module which has a constructor; but then user code's constructors
  73      would come first, and not be profiled.  */
  74   extern void __gmon_start__ (void) __attribute__ ((weak)); /*weak_extern (__gmon_start__);*/
  75
  76   __gmon_start__ ();
  77
  78   asm ("ALIGN");
  79   asm("END_INIT");
  80   /* Now the epilog. */
  81   asm ("\n/*@_init_PROLOG_ENDS*/");
  82   asm ("\n/*@_init_EPILOG_BEGINS*/");
  83   SECTION(".init");
  84 }
  85 asm ("END_INIT");
  86 SECTION(".text");
  87
  88 /* This version of __gmon_start__ is used if no other is found.  By providing
  89    a default function we avoid the need to test whether the pointer is NULL,
  90    which can be painful on some machines.  */
  91
  92 void __attribute__ ((weak))
  93 __gmon_start__ (void)
  94 {
  95   /* do nothing */
  96 }
  97
  98 /* End of the _init epilog, beginning of the _fini prolog. */
  99 asm ("\n/*@_init_EPILOG_ENDS*/");
 100 asm ("\n/*@_fini_PROLOG_BEGINS*/");
 101
 102 SECTION (".fini")
 103 void
 104 _fini (void)
 105 {
 106
 107   /* End of the _fini prolog. */
 108   asm ("ALIGN");
 109   asm ("END_FINI");
 110   asm ("\n/*@_fini_PROLOG_ENDS*/");
 111
 112   {
 113     /* Let GCC know that _fini is not a leaf function by having a dummy
 114        function call here.  We arrange for this call to be omitted from
 115        either crt file.  */
 116     extern void i_am_not_a_leaf (void);
 117     i_am_not_a_leaf ();
 118   }
 119
 120   /* Beginning of the _fini epilog. */
 121   asm ("\n/*@_fini_EPILOG_BEGINS*/");
 122   SECTION (".fini");
 123 }
 124 asm ("END_FINI");
 125
 126 /* End of the _fini epilog.  Any further generated assembly (e.g. .ident)
 127    is shared between both crt files. */
 128 asm ("\n/*@_fini_EPILOG_ENDS*/");
 129 asm ("\n/*@TRAILER_BEGINS*/");
 130
 131 /* End of file. */