libgcc/config/i386/cygming-crtbegin.c

   1 /* crtbegin object for windows32 targets.
   2    Copyright (C) 2007-2020 Free Software Foundation, Inc.
   3
   4    Contributed by Danny Smith <dannysmith@users.sourceforge.net>
   5
   6 This file is part of GCC.
   7
   8 GCC is free software; you can redistribute it and/or modify it under
   9 the terms of the GNU General Public License as published by the Free
  10 Software Foundation; either version 3, or (at your option) any later
  11 version.
  12
  13 GCC is distributed in the hope that it will be useful, but WITHOUT ANY
  14 WARRANTY; without even the implied warranty of MERCHANTABILITY or
  15 FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  16 for more details.
  17
  18 Under Section 7 of GPL version 3, you are granted additional
  19 permissions described in the GCC Runtime Library Exception, version
  20 3.1, as published by the Free Software Foundation.
  21
  22 You should have received a copy of the GNU General Public License and
  23 a copy of the GCC Runtime Library Exception along with this program;
  24 see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
  25 <http://www.gnu.org/licenses/>.  */
  26
  27 /* Target machine header files require this define. */
  28 #define IN_LIBGCC2
  29
  30 #include "auto-host.h"
  31 #include "tconfig.h"
  32 #include "tsystem.h"
  33 #include "coretypes.h"
  34 #include "tm.h"
  35 #include "libgcc_tm.h"
  36 #include "unwind-dw2-fde.h"
  37
  38 #define WIN32_LEAN_AND_MEAN
  39 #include <windows.h>
  40
  41 #ifndef LIBGCC_SONAME
  42 #define LIBGCC_SONAME "libgcc_s.dll"
  43 #endif
  44
  45 #if DWARF2_UNWIND_INFO
  46 /* Make the declarations weak.  This is critical for
  47    _Jv_RegisterClasses because it lives in libgcj.a  */
  48 extern void __register_frame_info (__attribute__((unused)) const void *,
  49                                    __attribute__((unused)) struct object *)
  50                                    TARGET_ATTRIBUTE_WEAK;
  51 extern void *__deregister_frame_info (__attribute__((unused)) const void *)
  52                                       TARGET_ATTRIBUTE_WEAK;
  53
  54 /* Work around for current cygwin32 build problems (Bug gas/16858).
  55    Compile weak default functions only for 64-bit systems,
  56    when absolutely necessary.  */
  57 #ifdef __x86_64__
  58 TARGET_ATTRIBUTE_WEAK void
  59 __register_frame_info (__attribute__((unused)) const void *p,
  60                        __attribute__((unused)) struct object *o)
  61 {
  62 }
  63
  64 TARGET_ATTRIBUTE_WEAK void *
  65 __deregister_frame_info (__attribute__((unused)) const void *p)
  66 {
  67   return (void*) 0;
  68 }
  69 #endif
  70 #endif /* DWARF2_UNWIND_INFO */
  71
  72 #if defined(HAVE_LD_RO_RW_SECTION_MIXING)
  73 # define EH_FRAME_SECTION_CONST const
  74 #else
  75 # define EH_FRAME_SECTION_CONST
  76 #endif
  77
  78 /* Stick a label at the beginning of the frame unwind info so we can
  79    register/deregister it with the exception handling library code.  */
  80 #if DWARF2_UNWIND_INFO
  81 static EH_FRAME_SECTION_CONST char __EH_FRAME_BEGIN__[]
  82   __attribute__((used, section(__LIBGCC_EH_FRAME_SECTION_NAME__), aligned(4)))
  83   = { };
  84
  85 static struct object obj;
  86
  87 /* Handle of libgcc's DLL reference.  */
  88 HANDLE hmod_libgcc;
  89 static void *  (*deregister_frame_fn) (const void *) = NULL;
  90 #endif
  91
  92 #ifdef __CYGWIN__
  93 /* Declare the __dso_handle variable.  It should have a unique value
  94    in every shared-object; in a main program its value is zero.  The
  95    object should in any case be protected.  This means the instance
  96    in one DSO or the main program is not used in another object.  The
  97    dynamic linker takes care of this.  */
  98
  99 #ifdef CRTSTUFFS_O
 100 extern void *__ImageBase;
 101 void *__dso_handle = &__ImageBase;
 102 #else
 103 void *__dso_handle = 0;
 104 #endif
 105
 106 #endif /* __CYGWIN__ */
 107
 108
 109 /* Pull in references from libgcc.a(unwind-dw2-fde.o) in the
 110    startfile. These are referenced by a ctor and dtor in crtend.o.  */
 111 extern void __gcc_register_frame (void);
 112 extern void __gcc_deregister_frame (void);
 113
 114 void
 115 __gcc_register_frame (void)
 116 {
 117 #if DWARF2_UNWIND_INFO
 118 /* Weak undefined symbols won't be pulled in from dlls; hence
 119    we first test if the dll is already loaded and, if so,
 120    get the symbol's address at run-time.  If the dll is not loaded,
 121    fallback to weak linkage to static archive.  */
 122
 123   void (*register_frame_fn) (const void *, struct object *);
 124   HANDLE h = GetModuleHandle (LIBGCC_SONAME);
 125
 126   if (h)
 127     {
 128       /* Increasing the load-count of LIBGCC_SONAME DLL.  */
 129       hmod_libgcc = LoadLibrary (LIBGCC_SONAME);
 130       register_frame_fn = (void (*) (const void *, struct object *))
 131                           GetProcAddress (h, "__register_frame_info");
 132       deregister_frame_fn = (void* (*) (const void *))
 133                             GetProcAddress (h, "__deregister_frame_info");
 134     }
 135   else
 136     {
 137       register_frame_fn = __register_frame_info;
 138       deregister_frame_fn = __deregister_frame_info;
 139     }
 140   if (register_frame_fn)
 141      register_frame_fn (__EH_FRAME_BEGIN__, &obj);
 142 #endif
 143
 144 #if DEFAULT_USE_CXA_ATEXIT
 145   /* If we use the __cxa_atexit method to register C++ dtors
 146      at object construction,  also use atexit to register eh frame
 147      info cleanup.  */
 148   atexit(__gcc_deregister_frame);
 149 #endif /* DEFAULT_USE_CXA_ATEXIT */
 150 }
 151
 152 void
 153 __gcc_deregister_frame (void)
 154 {
 155 #if DWARF2_UNWIND_INFO
 156   if (deregister_frame_fn)
 157      deregister_frame_fn (__EH_FRAME_BEGIN__);
 158   if (hmod_libgcc)
 159     FreeLibrary (hmod_libgcc);
 160 #endif
 161 }