gcc/crtstuff.c

   1 /* Specialized bits of code needed to support construction and
   2    destruction of file-scope objects in C++ code.
   3
   4    Written by Ron Guilmette (rfg@ncd.com) with help from Richard Stallman.
   5
   6 Copyright (C) 1991 Free Software Foundation, Inc.
   7
   8 This file is part of GNU CC.
   9
  10 GNU CC is free software; you can redistribute it and/or modify
  11 it under the terms of the GNU General Public License as published by
  12 the Free Software Foundation; either version 2, or (at your option)
  13 any later version.
  14
  15 GNU CC is distributed in the hope that it will be useful,
  16 but WITHOUT ANY WARRANTY; without even the implied warranty of
  17 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  18 GNU General Public License for more details.
  19
  20 You should have received a copy of the GNU General Public License
  21 along with GNU CC; see the file COPYING.  If not, write to
  22 the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.  */
  23
  24 /* As a special exception, if you link this library with files
  25    compiled with GCC to produce an executable, this does not cause
  26    the resulting executable to be covered by the GNU General Public License.
  27    This exception does not however invalidate any other reasons why
  28    the executable file might be covered by the GNU General Public License.  */
  29
  30 /* This file is a bit like libgcc1.c/libgcc2.c in that it is compiled
  31    multiple times and yields multiple .o files.
  32
  33    This file is useful on target machines where the object file format
  34    supports multiple "user-defined" sections (e.g. COFF, ELF, ROSE).  On
  35    such systems, this file allows us to avoid running collect (or any
  36    other such slow and painful kludge).  Additionally, if the target
  37    system supports a .init section, this file allows us to support the
  38    linking of C++ code with a non-C++ main program.
  39
  40    Note that if INIT_SECTION_ASM_OP is defined in the tm.h file, then
  41    this file *will* make use of the .init section.  If that symbol is
  42    not defined however, then the .init section will not be used.
  43
  44    Currently, only ELF is actually supported.
  45    The other formats probably need just alternative macro definitions.
  46
  47    This file must be compiled with gcc.  */
  48
  49 /* It is incorrect to include config.h here, because this file is being
  50    compiled for the target, and hence definitions concerning only the host
  51    do not apply.  */
  52
  53 #include "tm.h"
  54
  55 #ifndef CTORS_SECTION_ASM_OP
  56 #define CTORS_SECTION_ASM_OP    ".section\t.ctors,\"a\",@progbits"
  57 #endif
  58 #ifndef DTORS_SECTION_ASM_OP
  59 #define DTORS_SECTION_ASM_OP    ".section\t.dtors,\"a\",@progbits"
  60 #endif
  61
  62 #include "gbl-ctors.h"
  63
  64 #ifndef ON_EXIT
  65 #define ON_EXIT(a, b)
  66 #endif
  67
  68 #ifdef CRT_BEGIN
  69
  70 #ifdef INIT_SECTION_ASM_OP
  71
  72 /* The function __do_global_ctors_aux is compiled twice (once in crtbegin.o
  73    and once in crtend.o).  It must be declared static to avoid a link
  74    error.  Here, we define __do_global_ctors as an externally callable
  75    function.  It is externally callable so that __main can invoke it when
  76    INVOKE__main is defined.  This has the additional effect of forcing cc1
  77    to switch to the .text section.  */
  78 static void __do_global_ctors_aux ();
  79 void __do_global_ctors () { __do_global_ctors_aux (); }
  80
  81 asm (INIT_SECTION_ASM_OP);      /* cc1 doesn't know that we are switching! */
  82
  83 /* On some svr4 systems, the .init section preamble code provided in
  84    crti.o may do some evil things which we have to undo before we reach
  85    the function prologue code for __do_global_ctors (directly below).
  86    For such systems, define the macro INIT_SECTION_PREAMBLE to
  87    expand into the code needed to undo the actions of the crti.o file.  */
  88
  89 #ifdef INIT_SECTION_PREAMBLE
  90   INIT_SECTION_PREAMBLE;
  91 #endif
  92
  93 /* A routine to invoke all of the global constructors upon entry to the
  94    program.  We put this into the .init section (for systems that have
  95    such a thing) so that we can properly perform the construction of
  96    file-scope static-storage C++ objects within shared libraries.   */
  97
  98 static void
  99 __do_global_ctors_aux ()        /* prologue goes in .init section */
 100 {
 101   asm (TEXT_SECTION_ASM_OP);    /* don't put epilogue and body in .init */
 102   DO_GLOBAL_CTORS_BODY;
 103   ON_EXIT (__do_global_dtors, 0);
 104 }
 105
 106 #endif /* defined(INIT_SECTION_ASM_OP) */
 107
 108 /* Force cc1 to switch to .data section.  */
 109 static func_ptr force_to_data[0] = { };
 110
 111 /* The -1 is a flag to __do_global_[cd]tors
 112    indicating that this table does not start with a count of elements.  */
 113 #ifdef CTOR_LIST_BEGIN
 114 CTOR_LIST_BEGIN;
 115 #else
 116 asm (CTORS_SECTION_ASM_OP);     /* cc1 doesn't know that we are switching! */
 117 func_ptr __CTOR_LIST__[1] = { (func_ptr) (-1) };
 118 #endif
 119
 120 #ifdef DTOR_LIST_BEGIN
 121 DTOR_LIST_BEGIN;
 122 #else
 123 asm (DTORS_SECTION_ASM_OP);     /* cc1 doesn't know that we are switching! */
 124 func_ptr __DTOR_LIST__[1] = { (func_ptr) (-1) };
 125 #endif
 126
 127 #endif /* defined(CRT_BEGIN) */
 128
 129 #ifdef CRT_END
 130
 131 #ifdef INIT_SECTION_ASM_OP
 132
 133 /* A routine to invoke all of the global constructors upon entry to the
 134    program.  We put this into the .init section (for systems that have
 135    such a thing) so that we can properly perform the construction of
 136    file-scope static-storage C++ objects within shared libraries.
 137
 138    This must be virtually identical to the one above so that we can
 139    insure that the function prologue from the one above works correctly
 140    with the epilogue from this one.  (They will both go into the .init
 141    section as the first and last things (respectively) that the linker
 142    will put in that section.)
 143 */
 144
 145 static void
 146 __do_global_ctors_aux ()        /* prologue goes in .text section */
 147 {
 148   asm (INIT_SECTION_ASM_OP);
 149   DO_GLOBAL_CTORS_BODY;
 150   ON_EXIT (__do_global_dtors, 0);
 151 }                               /* epilogue and body go in .init section */
 152
 153 #endif /* defined(INIT_SECTION_ASM_OP) */
 154
 155 /* Force cc1 to switch to .data section.  */
 156 static func_ptr force_to_data[0] = { };
 157
 158 #ifdef CTOR_LIST_END
 159 CTOR_LIST_END;
 160 #else
 161 asm (CTORS_SECTION_ASM_OP);     /* cc1 doesn't know that we are switching! */
 162 func_ptr __CTOR_END__[1] = { (func_ptr) 0 };
 163 #endif
 164
 165 #ifdef DTOR_LIST_END
 166 DTOR_LIST_END;
 167 #else
 168 asm (DTORS_SECTION_ASM_OP);     /* cc1 doesn't know that we are switching! */
 169 func_ptr __DTOR_END__[1] = { (func_ptr) 0 };
 170 #endif
 171
 172 #endif /* defined(CRT_END) */