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 ()
  80 {
  81 #ifdef INVOKE__main  /* If __main won't actually call __do_global_ctors
  82                         then it doesn't matter what's inside the function.
  83                         The inside of __do_global_ctors_aux is called
  84                         automatically in that case.
  85                         And the Alliant fx2800 linker crashes
  86                         on this reference.  So prevent the crash.  */
  87   __do_global_ctors_aux ();
  88 #endif
  89 }
  90
  91 asm (INIT_SECTION_ASM_OP);      /* cc1 doesn't know that we are switching! */
  92
  93 /* On some svr4 systems, the .init section preamble code provided in
  94    crti.o may do some evil things which we have to undo before we reach
  95    the function prologue code for __do_global_ctors (directly below).
  96    For such systems, define the macro INIT_SECTION_PREAMBLE to
  97    expand into the code needed to undo the actions of the crti.o file.  */
  98
  99 #ifdef INIT_SECTION_PREAMBLE
 100   INIT_SECTION_PREAMBLE;
 101 #endif
 102
 103 /* A routine to invoke all of the global constructors upon entry to the
 104    program.  We put this into the .init section (for systems that have
 105    such a thing) so that we can properly perform the construction of
 106    file-scope static-storage C++ objects within shared libraries.   */
 107
 108 static void
 109 __do_global_ctors_aux ()        /* prologue goes in .init section */
 110 {
 111   asm (TEXT_SECTION_ASM_OP);    /* don't put epilogue and body in .init */
 112   DO_GLOBAL_CTORS_BODY;
 113   ON_EXIT (__do_global_dtors, 0);
 114 }
 115
 116 #endif /* defined(INIT_SECTION_ASM_OP) */
 117
 118 /* Force cc1 to switch to .data section.  */
 119 static func_ptr force_to_data[0] = { };
 120
 121 /* The -1 is a flag to __do_global_[cd]tors
 122    indicating that this table does not start with a count of elements.  */
 123 #ifdef CTOR_LIST_BEGIN
 124 CTOR_LIST_BEGIN;
 125 #else
 126 asm (CTORS_SECTION_ASM_OP);     /* cc1 doesn't know that we are switching! */
 127 func_ptr __CTOR_LIST__[1] = { (func_ptr) (-1) };
 128 #endif
 129
 130 #ifdef DTOR_LIST_BEGIN
 131 DTOR_LIST_BEGIN;
 132 #else
 133 asm (DTORS_SECTION_ASM_OP);     /* cc1 doesn't know that we are switching! */
 134 func_ptr __DTOR_LIST__[1] = { (func_ptr) (-1) };
 135 #endif
 136
 137 #endif /* defined(CRT_BEGIN) */
 138
 139 #ifdef CRT_END
 140
 141 #ifdef INIT_SECTION_ASM_OP
 142
 143 /* A routine to invoke all of the global constructors upon entry to the
 144    program.  We put this into the .init section (for systems that have
 145    such a thing) so that we can properly perform the construction of
 146    file-scope static-storage C++ objects within shared libraries.
 147
 148    This must be virtually identical to the one above so that we can
 149    insure that the function prologue from the one above works correctly
 150    with the epilogue from this one.  (They will both go into the .init
 151    section as the first and last things (respectively) that the linker
 152    will put in that section.)
 153 */
 154
 155 static void
 156 __do_global_ctors_aux ()        /* prologue goes in .text section */
 157 {
 158   asm (INIT_SECTION_ASM_OP);
 159   DO_GLOBAL_CTORS_BODY;
 160   ON_EXIT (__do_global_dtors, 0);
 161 }                               /* epilogue and body go in .init section */
 162
 163 #endif /* defined(INIT_SECTION_ASM_OP) */
 164
 165 /* Force cc1 to switch to .data section.  */
 166 static func_ptr force_to_data[0] = { };
 167
 168 #ifdef CTOR_LIST_END
 169 CTOR_LIST_END;
 170 #else
 171 asm (CTORS_SECTION_ASM_OP);     /* cc1 doesn't know that we are switching! */
 172 func_ptr __CTOR_END__[1] = { (func_ptr) 0 };
 173 #endif
 174
 175 #ifdef DTOR_LIST_END
 176 DTOR_LIST_END;
 177 #else
 178 asm (DTORS_SECTION_ASM_OP);     /* cc1 doesn't know that we are switching! */
 179 func_ptr __DTOR_END__[1] = { (func_ptr) 0 };
 180 #endif
 181
 182 #endif /* defined(CRT_END) */