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@netcom.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 and COFF are supported.  It is likely however that
  45    ROSE could also be supported, if someone was willing to do the work to
  46    make whatever (small?) adaptations are needed.  (Some work may be
  47    needed on the ROSE assembler and linker also.)
  48
  49    This file must be compiled with gcc.  */
  50
  51 /* It is incorrect to include config.h here, because this file is being
  52    compiled for the target, and hence definitions concerning only the host
  53    do not apply.  */
  54
  55 #include "tm.h"
  56
  57 #ifndef CTORS_SECTION_ASM_OP
  58 #define CTORS_SECTION_ASM_OP    ".section\t.ctors,\"a\",@progbits"
  59 #endif
  60 #ifndef DTORS_SECTION_ASM_OP
  61 #define DTORS_SECTION_ASM_OP    ".section\t.dtors,\"a\",@progbits"
  62 #endif
  63
  64 #include "gbl-ctors.h"
  65
  66 #ifndef ON_EXIT
  67 #define ON_EXIT(a, b)
  68 #endif
  69
  70 #ifdef CRT_BEGIN
  71
  72 #ifdef INIT_SECTION_ASM_OP
  73
  74 /* The function __do_global_ctors_aux is compiled twice (once in crtbegin.o
  75    and once in crtend.o).  It must be declared static to avoid a link
  76    error.  Here, we define __do_global_ctors as an externally callable
  77    function.  It is externally callable so that __main can invoke it when
  78    INVOKE__main is defined.  This has the additional effect of forcing cc1
  79    to switch to the .text section.  */
  80 static void __do_global_ctors_aux ();
  81 void __do_global_ctors ()
  82 {
  83 #ifdef INVOKE__main  /* If __main won't actually call __do_global_ctors
  84                         then it doesn't matter what's inside the function.
  85                         The inside of __do_global_ctors_aux is called
  86                         automatically in that case.
  87                         And the Alliant fx2800 linker crashes
  88                         on this reference.  So prevent the crash.  */
  89   __do_global_ctors_aux ();
  90 #endif
  91 }
  92
  93 asm (INIT_SECTION_ASM_OP);      /* cc1 doesn't know that we are switching! */
  94
  95 /* On some svr4 systems, the .init section preamble code provided in
  96    crti.o may do some evil things which we have to undo before we reach
  97    the function prologue code for __do_global_ctors (directly below).
  98    For such systems, define the macro INIT_SECTION_PREAMBLE to
  99    expand into the code needed to undo the actions of the crti.o file.  */
 100
 101 #ifdef INIT_SECTION_PREAMBLE
 102   INIT_SECTION_PREAMBLE;
 103 #endif
 104
 105 /* A routine to invoke all of the global constructors upon entry to the
 106    program.  We put this into the .init section (for systems that have
 107    such a thing) so that we can properly perform the construction of
 108    file-scope static-storage C++ objects within shared libraries.   */
 109
 110 static void
 111 __do_global_ctors_aux ()        /* prologue goes in .init section */
 112 {
 113 #ifdef FORCE_INIT_SECTION_ALIGN
 114   FORCE_INIT_SECTION_ALIGN;     /* Explicit align before switch to .text */
 115 #endif
 116   asm (TEXT_SECTION_ASM_OP);    /* don't put epilogue and body in .init */
 117   DO_GLOBAL_CTORS_BODY;
 118   ON_EXIT (__do_global_dtors, 0);
 119 }
 120
 121 #endif /* defined(INIT_SECTION_ASM_OP) */
 122
 123 /* Force cc1 to switch to .data section.  */
 124 static func_ptr force_to_data[0] = { };
 125
 126 /* The -1 is a flag to __do_global_[cd]tors
 127    indicating that this table does not start with a count of elements.  */
 128 #ifdef CTOR_LIST_BEGIN
 129 CTOR_LIST_BEGIN;
 130 #else
 131 asm (CTORS_SECTION_ASM_OP);     /* cc1 doesn't know that we are switching! */
 132 func_ptr __CTOR_LIST__[1] = { (func_ptr) (-1) };
 133 #endif
 134
 135 #ifdef DTOR_LIST_BEGIN
 136 DTOR_LIST_BEGIN;
 137 #else
 138 asm (DTORS_SECTION_ASM_OP);     /* cc1 doesn't know that we are switching! */
 139 func_ptr __DTOR_LIST__[1] = { (func_ptr) (-1) };
 140 #endif
 141
 142 #endif /* defined(CRT_BEGIN) */
 143
 144 #ifdef CRT_END
 145
 146 #ifdef INIT_SECTION_ASM_OP
 147
 148 /* A routine to invoke all of the global constructors upon entry to the
 149    program.  We put this into the .init section (for systems that have
 150    such a thing) so that we can properly perform the construction of
 151    file-scope static-storage C++ objects within shared libraries.
 152
 153    This must be virtually identical to the one above so that we can
 154    insure that the function prologue from the one above works correctly
 155    with the epilogue from this one.  (They will both go into the .init
 156    section as the first and last things (respectively) that the linker
 157    will put in that section.)
 158 */
 159
 160 static void
 161 __do_global_ctors_aux ()        /* prologue goes in .text section */
 162 {
 163   asm (INIT_SECTION_ASM_OP);
 164   DO_GLOBAL_CTORS_BODY;
 165   ON_EXIT (__do_global_dtors, 0);
 166 }                               /* epilogue and body go in .init section */
 167
 168 #endif /* defined(INIT_SECTION_ASM_OP) */
 169
 170 /* Force cc1 to switch to .data section.  */
 171 static func_ptr force_to_data[0] = { };
 172
 173 #ifdef CTOR_LIST_END
 174 CTOR_LIST_END;
 175 #else
 176 asm (CTORS_SECTION_ASM_OP);     /* cc1 doesn't know that we are switching! */
 177 func_ptr __CTOR_END__[1] = { (func_ptr) 0 };
 178 #endif
 179
 180 #ifdef DTOR_LIST_END
 181 DTOR_LIST_END;
 182 #else
 183 asm (DTORS_SECTION_ASM_OP);     /* cc1 doesn't know that we are switching! */
 184 func_ptr __DTOR_END__[1] = { (func_ptr) 0 };
 185 #endif
 186
 187 #endif /* defined(CRT_END) */