libstdc++-v3/libsupc++/vtv_stubs.cc

   1 // Copyright (C) 2012-2017 Free Software Foundation, Inc.
   2 //
   3 // This file is part of the GNU ISO C++ Library.  This library is free
   4 // software; you can redistribute it and/or modify it under the
   5 // terms of the GNU General Public License as published by the
   6 // Free Software Foundation; either version 3, or (at your option)
   7 // any later version.
   8
   9 // This library is distributed in the hope that it will be useful,
  10 // but WITHOUT ANY WARRANTY; without even the implied warranty of
  11 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12 // GNU General Public License for more details.
  13
  14 // Under Section 7 of GPL version 3, you are granted additional
  15 // permissions described in the GCC Runtime Library Exception, version
  16 // 3.1, as published by the Free Software Foundation.
  17
  18 // You should have received a copy of the GNU General Public License and
  19 // a copy of the GCC Runtime Library Exception along with this program;
  20 // see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
  21 // <http://www.gnu.org/licenses/>.
  22
  23 /* This is part of the vtable verification runtime library.  For more
  24    information about this feature, see the comments in libvtv/vtv_rts.cc.  */
  25
  26 /* The functions in this file are used to create the libvtv_stubs
  27    library, as part of the vtable verification feature.  When building
  28    a binary without vtable verification, and linking it with a
  29    (possibly pre-built third-party) library that was built with
  30    verification, it is possible that vtable verification will fail due
  31    to incomplete data (rather than due to corrupt vtable pointers).  In
  32    this case we need to give programmers a way of turning off the
  33    vtable verification in their libraries.  They can do so by linking
  34    with the libvtv_stubs library, which (as you can see) will replace
  35    the real verification functions with a set of functions that do
  36    nothing (so no more verification failures/aborts).  */
  37
  38 #include <cstddef>
  39
  40 /* weak symbols on Windows work differently than on Linux. To be able
  41    to switch vtv on and off on Windows two dlls are built. One with
  42    the sources from libvtv, the other from these stubs. Depending on
  43    which dll is placed in the folder of the executable the functions
  44    from libvtv or the stubs functions are used. */
  45 #if defined (__CYGWIN__) || defined (__MINGW32__)
  46 extern "C"
  47 void
  48 __VLTChangePermission(int);
  49
  50 void
  51 __VLTRegisterSet(void**, const void*, std::size_t, std::size_t,
  52                  void**);
  53
  54 void
  55 __VLTRegisterPair(void**, const void*, std::size_t,
  56                   const void*);
  57
  58 const void*
  59 __VLTVerifyVtablePointer(void**, const void*);
  60
  61 void
  62 __VLTRegisterSetDebug(void**, const void*, std::size_t, std::size_t,
  63                       void**);
  64
  65 void
  66 __VLTRegisterPairDebug(void**, const void*, std::size_t, const void*,
  67                        const char*, const char*);
  68
  69 const void*
  70 __VLTVerifyVtablePointerDebug(void**, const void*, const char*,
  71                               const char*);
  72 #else
  73 // Declare as weak for libsupc++, strong definitions are in libvtv.
  74 #if __GXX_WEAK__
  75 extern "C"
  76 void
  77 __VLTChangePermission(int) __attribute__((weak));
  78
  79 void
  80 __VLTRegisterSet(void**, const void*, std::size_t, std::size_t,
  81                  void**) __attribute__((weak));
  82
  83 void
  84 __VLTRegisterPair(void**, const void*, std::size_t,
  85                   const void*) __attribute__((weak));
  86
  87 const void*
  88 __VLTVerifyVtablePointer(void**, const void*) __attribute__((weak));
  89
  90 void
  91 __VLTRegisterSetDebug(void**, const void*, std::size_t, std::size_t,
  92                       void**) __attribute__((weak));
  93
  94 void
  95 __VLTRegisterPairDebug(void**, const void*, std::size_t, const void*,
  96                        const char*, const char*) __attribute__((weak));
  97
  98 const void*
  99 __VLTVerifyVtablePointerDebug(void**, const void*, const char*,
 100                               const char*) __attribute__((weak));
 101 #endif
 102 #endif
 103
 104 // Stub definitions.
 105 extern "C"
 106 void
 107 __VLTChangePermission(int)
 108 { }
 109
 110 void
 111 __VLTRegisterSet(void**, const void*, std::size_t, std::size_t, void**)
 112 { }
 113
 114 void
 115 __VLTRegisterPair(void**, const void*, std::size_t, const void*)
 116 { }
 117
 118 const void*
 119 __VLTVerifyVtablePointer(void**, const void* vtable_ptr)
 120 { return vtable_ptr; }
 121
 122 void
 123 __VLTRegisterSetDebug(void**, const void*, std::size_t, std::size_t, void**)
 124 { }
 125
 126 void
 127 __VLTRegisterPairDebug(void**, const void*, std::size_t, const void*,
 128                        const char*, const  char*)
 129 { }
 130
 131 const void*
 132 __VLTVerifyVtablePointerDebug(void**, const void* vtable_ptr, const char*,
 133                               const char*)
 134 { return vtable_ptr; }