gdb/common/poison.h

   1 /* Poison symbols at compile time.
   2
   3    Copyright (C) 2017 Free Software Foundation, Inc.
   4
   5    This file is part of GDB.
   6
   7    This program is free software; you can redistribute it and/or modify
   8    it under the terms of the GNU General Public License as published by
   9    the Free Software Foundation; either version 3 of the License, or
  10    (at your option) any later version.
  11
  12    This program is distributed in the hope that it will be useful,
  13    but WITHOUT ANY WARRANTY; without even the implied warranty of
  14    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15    GNU General Public License for more details.
  16
  17    You should have received a copy of the GNU General Public License
  18    along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
  19
  20 #ifndef COMMON_POISON_H
  21 #define COMMON_POISON_H
  22
  23 #include "traits.h"
  24
  25 /* Poison memset of non-POD types.  The idea is catching invalid
  26    initialization of non-POD structs that is easy to be introduced as
  27    side effect of refactoring.  For example, say this:
  28
  29  struct S { VEC(foo_s) *m_data; };
  30
  31 is converted to this at some point:
  32
  33  struct S {
  34    S() { m_data.reserve (10); }
  35    std::vector<foo> m_data;
  36  };
  37
  38 and old code was initializing S objects like this:
  39
  40  struct S s;
  41  memset (&s, 0, sizeof (S)); // whoops, now wipes vector.
  42
  43 Declaring memset as deleted for non-POD types makes the memset above
  44 be a compile-time error.  */
  45
  46 /* Helper for SFINAE.  True if "T *" is memsettable.  I.e., if T is
  47    either void, or POD.  */
  48 template<typename T>
  49 struct IsMemsettable
  50   : gdb::Or<std::is_void<T>,
  51             std::is_pod<T>>
  52 {};
  53
  54 template <typename T,
  55           typename = gdb::Requires<gdb::Not<IsMemsettable<T>>>>
  56 void *memset (T *s, int c, size_t n) = delete;
  57
  58 #if HAVE_IS_TRIVIALLY_COPYABLE
  59
  60 /* Similarly, poison memcpy and memmove of non trivially-copyable
  61    types, which is undefined.  */
  62
  63 /* True if "T *" is relocatable.  I.e., copyable with memcpy/memmove.
  64    I.e., T is either trivially copyable, or void.  */
  65 template<typename T>
  66 struct IsRelocatable
  67   : gdb::Or<std::is_void<T>,
  68             std::is_trivially_copyable<T>>
  69 {};
  70
  71 /* True if both source and destination are relocatable.  */
  72
  73 template <typename D, typename S>
  74 using BothAreRelocatable
  75   = gdb::And<IsRelocatable<D>, IsRelocatable<S>>;
  76
  77 template <typename D, typename S,
  78           typename = gdb::Requires<gdb::Not<BothAreRelocatable<D, S>>>>
  79 void *memcpy (D *dest, const S *src, size_t n) = delete;
  80
  81 template <typename D, typename S,
  82           typename = gdb::Requires<gdb::Not<BothAreRelocatable<D, S>>>>
  83 void *memmove (D *dest, const S *src, size_t n) = delete;
  84
  85 #endif /* HAVE_IS_TRIVIALLY_COPYABLE */
  86
  87 #endif /* COMMON_POISON_H */