gdbsupport/enum-flags.h

   1 /* Copyright (C) 2015-2023 Free Software Foundation, Inc.
   2
   3    This file is part of GDB.
   4
   5    This program is free software; you can redistribute it and/or modify
   6    it under the terms of the GNU General Public License as published by
   7    the Free Software Foundation; either version 3 of the License, or
   8    (at your option) any later version.
   9
  10    This program is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  13    GNU General Public License for more details.
  14
  15    You should have received a copy of the GNU General Public License
  16    along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
  17
  18 #ifndef COMMON_ENUM_FLAGS_H
  19 #define COMMON_ENUM_FLAGS_H
  20
  21 #include "traits.h"
  22
  23 /* Type-safe wrapper for enum flags.  enum flags are enums where the
  24    values are bits that are meant to be ORed together.
  25
  26    This allows writing code like the below, while with raw enums this
  27    would fail to compile without casts to enum type at the assignments
  28    to 'f':
  29
  30     enum some_flag
  31     {
  32        flag_val1 = 1 << 1,
  33        flag_val2 = 1 << 2,
  34        flag_val3 = 1 << 3,
  35        flag_val4 = 1 << 4,
  36     };
  37     DEF_ENUM_FLAGS_TYPE(enum some_flag, some_flags);
  38
  39     some_flags f = flag_val1 | flag_val2;
  40     f |= flag_val3;
  41
  42    It's also possible to assign literal zero to an enum flags variable
  43    (meaning, no flags), dispensing adding an awkward explicit "no
  44    value" value to the enumeration.  For example:
  45
  46     some_flags f = 0;
  47     f |= flag_val3 | flag_val4;
  48
  49    Note that literal integers other than zero fail to compile:
  50
  51     some_flags f = 1; // error
  52 */
  53
  54 #ifdef __cplusplus
  55
  56 /* Use this to mark an enum as flags enum.  It defines FLAGS_TYPE as
  57    enum_flags wrapper class for ENUM, and enables the global operator
  58    overloads for ENUM.  */
  59 #define DEF_ENUM_FLAGS_TYPE(enum_type, flags_type)      \
  60   typedef enum_flags<enum_type> flags_type;             \
  61   void is_enum_flags_enum_type (enum_type *)
  62
  63 /* To enable the global enum_flags operators for enum, declare an
  64    "is_enum_flags_enum_type" overload that has exactly one parameter,
  65    of type a pointer to that enum class.  E.g.,:
  66
  67      void is_enum_flags_enum_type (enum some_flag *);
  68
  69    The function does not need to be defined, only declared.
  70    DEF_ENUM_FLAGS_TYPE declares this.
  71
  72    A function declaration is preferred over a traits type, because the
  73    former allows calling the DEF_ENUM_FLAGS_TYPE macro inside a
  74    namespace to define the corresponding enum flags type in that
  75    namespace.  The compiler finds the corresponding
  76    is_enum_flags_enum_type function via ADL.  */
  77
  78 /* Note that std::underlying_type<enum_type> is not what we want here,
  79    since that returns unsigned int even when the enum decays to signed
  80    int.  */
  81 template<int size, bool sign> class integer_for_size { typedef void type; };
  82 template<> struct integer_for_size<1, 0> { typedef uint8_t type; };
  83 template<> struct integer_for_size<2, 0> { typedef uint16_t type; };
  84 template<> struct integer_for_size<4, 0> { typedef uint32_t type; };
  85 template<> struct integer_for_size<8, 0> { typedef uint64_t type; };
  86 template<> struct integer_for_size<1, 1> { typedef int8_t type; };
  87 template<> struct integer_for_size<2, 1> { typedef int16_t type; };
  88 template<> struct integer_for_size<4, 1> { typedef int32_t type; };
  89 template<> struct integer_for_size<8, 1> { typedef int64_t type; };
  90
  91 template<typename T>
  92 struct enum_underlying_type
  93 {
  94   DIAGNOSTIC_PUSH
  95   DIAGNOSTIC_IGNORE_ENUM_CONSTEXPR_CONVERSION
  96   typedef typename
  97     integer_for_size<sizeof (T), static_cast<bool>(T (-1) < T (0))>::type
  98     type;
  99   DIAGNOSTIC_POP
 100 };
 101
 102 namespace enum_flags_detail
 103 {
 104
 105 /* Private type used to support initializing flag types with zero:
 106
 107    foo_flags f = 0;
 108
 109    but not other integers:
 110
 111    foo_flags f = 1;
 112
 113    The way this works is that we define an implicit constructor that
 114    takes a pointer to this private type.  Since nothing can
 115    instantiate an object of this type, the only possible pointer to
 116    pass to the constructor is the NULL pointer, or, zero.  */
 117 struct zero_type;
 118
 119 /* gdb::Requires trait helpers.  */
 120 template <typename enum_type>
 121 using EnumIsUnsigned
 122   = std::is_unsigned<typename enum_underlying_type<enum_type>::type>;
 123 template <typename enum_type>
 124 using EnumIsSigned
 125   = std::is_signed<typename enum_underlying_type<enum_type>::type>;
 126
 127 }
 128
 129 template <typename E>
 130 class enum_flags
 131 {
 132 public:
 133   typedef E enum_type;
 134   typedef typename enum_underlying_type<enum_type>::type underlying_type;
 135
 136   /* For to_string.  Maps one enumerator of E to a string.  */
 137   struct string_mapping
 138   {
 139     E flag;
 140     const char *str;
 141   };
 142
 143   /* Convenience for to_string implementations, to build a
 144      string_mapping array.  */
 145 #define MAP_ENUM_FLAG(ENUM_FLAG) { ENUM_FLAG, #ENUM_FLAG }
 146
 147 public:
 148   /* Allow default construction.  */
 149   constexpr enum_flags ()
 150     : m_enum_value ((enum_type) 0)
 151   {}
 152
 153   /* The default move/copy ctor/assignment do the right thing.  */
 154
 155   /* If you get an error saying these two overloads are ambiguous,
 156      then you tried to mix values of different enum types.  */
 157   constexpr enum_flags (enum_type e)
 158     : m_enum_value (e)
 159   {}
 160   constexpr enum_flags (enum_flags_detail::zero_type *zero)
 161     : m_enum_value ((enum_type) 0)
 162   {}
 163
 164   enum_flags &operator&= (enum_flags e) &
 165   {
 166     m_enum_value = (enum_type) (m_enum_value & e.m_enum_value);
 167     return *this;
 168   }
 169   enum_flags &operator|= (enum_flags e) &
 170   {
 171     m_enum_value = (enum_type) (m_enum_value | e.m_enum_value);
 172     return *this;
 173   }
 174   enum_flags &operator^= (enum_flags e) &
 175   {
 176     m_enum_value = (enum_type) (m_enum_value ^ e.m_enum_value);
 177     return *this;
 178   }
 179
 180   /* Delete rval versions.  */
 181   void operator&= (enum_flags e) && = delete;
 182   void operator|= (enum_flags e) && = delete;
 183   void operator^= (enum_flags e) && = delete;
 184
 185   /* Like raw enums, allow conversion to the underlying type.  */
 186   constexpr operator underlying_type () const
 187   {
 188     return m_enum_value;
 189   }
 190
 191   /* Get the underlying value as a raw enum.  */
 192   constexpr enum_type raw () const
 193   {
 194     return m_enum_value;
 195   }
 196
 197   /* Binary operations involving some unrelated type (which would be a
 198      bug) are implemented as non-members, and deleted.  */
 199
 200   /* Convert this object to a std::string, using MAPPING as
 201      enumerator-to-string mapping array.  This is not meant to be
 202      called directly.  Instead, enum_flags specializations should have
 203      their own to_string function wrapping this one, thus hiding the
 204      mapping array from callers.
 205
 206      Note: this is defined outside the template class so it can use
 207      the global operators for enum_type, which are only defined after
 208      the template class.  */
 209   template<size_t N>
 210   std::string to_string (const string_mapping (&mapping)[N]) const;
 211
 212 private:
 213   /* Stored as enum_type because GDB knows to print the bit flags
 214      neatly if the enum values look like bit flags.  */
 215   enum_type m_enum_value;
 216 };
 217
 218 template <typename E>
 219 using is_enum_flags_enum_type_t
 220   = decltype (is_enum_flags_enum_type (std::declval<E *> ()));
 221
 222 /* Global operator overloads.  */
 223
 224 /* Generate binary operators.  */
 225
 226 #define ENUM_FLAGS_GEN_BINOP(OPERATOR_OP, OP)                           \
 227                                                                         \
 228   /* Raw enum on both LHS/RHS.  Returns raw enum type.  */              \
 229   template <typename enum_type,                                         \
 230             typename = is_enum_flags_enum_type_t<enum_type>>            \
 231   constexpr enum_type                                                   \
 232   OPERATOR_OP (enum_type e1, enum_type e2)                              \
 233   {                                                                     \
 234     using underlying = typename enum_flags<enum_type>::underlying_type; \
 235     return (enum_type) (underlying (e1) OP underlying (e2));            \
 236   }                                                                     \
 237                                                                         \
 238   /* enum_flags on the LHS.  */                                         \
 239   template <typename enum_type,                                         \
 240             typename = is_enum_flags_enum_type_t<enum_type>>            \
 241   constexpr enum_flags<enum_type>                                       \
 242   OPERATOR_OP (enum_flags<enum_type> e1, enum_type e2)                  \
 243   { return e1.raw () OP e2; }                                           \
 244                                                                         \
 245   /* enum_flags on the RHS.  */                                         \
 246   template <typename enum_type,                                         \
 247             typename = is_enum_flags_enum_type_t<enum_type>>            \
 248   constexpr enum_flags<enum_type>                                       \
 249   OPERATOR_OP (enum_type e1, enum_flags<enum_type> e2)                  \
 250   { return e1 OP e2.raw (); }                                           \
 251                                                                         \
 252   /* enum_flags on both LHS/RHS.  */                                    \
 253   template <typename enum_type,                                         \
 254             typename = is_enum_flags_enum_type_t<enum_type>>            \
 255   constexpr enum_flags<enum_type>                                       \
 256   OPERATOR_OP (enum_flags<enum_type> e1, enum_flags<enum_type> e2)      \
 257   { return e1.raw () OP e2.raw (); }                                    \
 258                                                                         \
 259   /* Delete cases involving unrelated types.  */                        \
 260                                                                         \
 261   template <typename enum_type, typename unrelated_type,                \
 262             typename = is_enum_flags_enum_type_t<enum_type>>            \
 263   constexpr enum_flags<enum_type>                                       \
 264   OPERATOR_OP (enum_type e1, unrelated_type e2) = delete;               \
 265                                                                         \
 266   template <typename enum_type, typename unrelated_type,                \
 267             typename = is_enum_flags_enum_type_t<enum_type>>            \
 268   constexpr enum_flags<enum_type>                                       \
 269   OPERATOR_OP (unrelated_type e1, enum_type e2) = delete;               \
 270                                                                         \
 271   template <typename enum_type, typename unrelated_type,                \
 272             typename = is_enum_flags_enum_type_t<enum_type>>            \
 273   constexpr enum_flags<enum_type>                                       \
 274   OPERATOR_OP (enum_flags<enum_type> e1, unrelated_type e2) = delete;   \
 275                                                                         \
 276   template <typename enum_type, typename unrelated_type,                \
 277             typename = is_enum_flags_enum_type_t<enum_type>>            \
 278   constexpr enum_flags<enum_type>                                       \
 279   OPERATOR_OP (unrelated_type e1, enum_flags<enum_type> e2) = delete;
 280
 281 /* Generate non-member compound assignment operators.  Only the raw
 282    enum versions are defined here.  The enum_flags versions are
 283    defined as member functions, simply because it's less code that
 284    way.
 285
 286    Note we delete operators that would allow e.g.,
 287
 288      "enum_type | 1" or "enum_type1 | enum_type2"
 289
 290    because that would allow a mistake like :
 291      enum flags1 { F1_FLAGS1 = 1 };
 292      enum flags2 { F2_FLAGS2 = 2 };
 293      enum flags1 val;
 294      switch (val) {
 295        case F1_FLAGS1 | F2_FLAGS2:
 296      ...
 297
 298    If you really need to 'or' enumerators of different flag types,
 299    cast to integer first.
 300 */
 301 #define ENUM_FLAGS_GEN_COMPOUND_ASSIGN(OPERATOR_OP, OP)                 \
 302   /* lval reference version.  */                                        \
 303   template <typename enum_type,                                         \
 304             typename = is_enum_flags_enum_type_t<enum_type>>            \
 305   constexpr enum_type &                                                 \
 306   OPERATOR_OP (enum_type &e1, enum_type e2)                             \
 307   { return e1 = e1 OP e2; }                                             \
 308                                                                         \
 309   /* rval reference version.  */                                        \
 310   template <typename enum_type,                                         \
 311             typename = is_enum_flags_enum_type_t<enum_type>>            \
 312   void                                                                  \
 313   OPERATOR_OP (enum_type &&e1, enum_type e2) = delete;                  \
 314                                                                         \
 315   /* Delete compound assignment from unrelated types.  */               \
 316                                                                         \
 317   template <typename enum_type, typename other_enum_type,               \
 318             typename = is_enum_flags_enum_type_t<enum_type>>            \
 319   constexpr enum_type &                                                 \
 320   OPERATOR_OP (enum_type &e1, other_enum_type e2) = delete;             \
 321                                                                         \
 322   template <typename enum_type, typename other_enum_type,               \
 323             typename = is_enum_flags_enum_type_t<enum_type>>            \
 324   void                                                                  \
 325   OPERATOR_OP (enum_type &&e1, other_enum_type e2) = delete;
 326
 327 ENUM_FLAGS_GEN_BINOP (operator|, |)
 328 ENUM_FLAGS_GEN_BINOP (operator&, &)
 329 ENUM_FLAGS_GEN_BINOP (operator^, ^)
 330
 331 ENUM_FLAGS_GEN_COMPOUND_ASSIGN (operator|=, |)
 332 ENUM_FLAGS_GEN_COMPOUND_ASSIGN (operator&=, &)
 333 ENUM_FLAGS_GEN_COMPOUND_ASSIGN (operator^=, ^)
 334
 335 /* Allow comparison with enum_flags, raw enum, and integers, only.
 336    The latter case allows "== 0".  As side effect, it allows comparing
 337    with integer variables too, but that's not a common mistake to
 338    make.  It's important to disable comparison with unrelated types to
 339    prevent accidentally comparing with unrelated enum values, which
 340    are convertible to integer, and thus coupled with enum_flags
 341    conversion to underlying type too, would trigger the built-in 'bool
 342    operator==(unsigned, int)' operator.  */
 343
 344 #define ENUM_FLAGS_GEN_COMP(OPERATOR_OP, OP)                            \
 345                                                                         \
 346   /* enum_flags OP enum_flags */                                        \
 347                                                                         \
 348   template <typename enum_type>                                         \
 349   constexpr bool                                                        \
 350   OPERATOR_OP (enum_flags<enum_type> lhs, enum_flags<enum_type> rhs)    \
 351   { return lhs.raw () OP rhs.raw (); }                                  \
 352                                                                         \
 353   /* enum_flags OP other */                                             \
 354                                                                         \
 355   template <typename enum_type>                                         \
 356   constexpr bool                                                        \
 357   OPERATOR_OP (enum_flags<enum_type> lhs, enum_type rhs)                \
 358   { return lhs.raw () OP rhs; }                                         \
 359                                                                         \
 360   template <typename enum_type>                                         \
 361   constexpr bool                                                        \
 362   OPERATOR_OP (enum_flags<enum_type> lhs, int rhs)                      \
 363   { return lhs.raw () OP rhs; }                                         \
 364                                                                         \
 365   template <typename enum_type, typename U>                             \
 366   constexpr bool                                                        \
 367   OPERATOR_OP (enum_flags<enum_type> lhs, U rhs) = delete;              \
 368                                                                         \
 369   /* other OP enum_flags */                                             \
 370                                                                         \
 371   template <typename enum_type>                                         \
 372   constexpr bool                                                        \
 373   OPERATOR_OP (enum_type lhs, enum_flags<enum_type> rhs)                \
 374   { return lhs OP rhs.raw (); }                                         \
 375                                                                         \
 376   template <typename enum_type>                                         \
 377   constexpr bool                                                        \
 378   OPERATOR_OP (int lhs, enum_flags<enum_type> rhs)                      \
 379   { return lhs OP rhs.raw (); }                                         \
 380                                                                         \
 381   template <typename enum_type, typename U>                             \
 382   constexpr bool                                                        \
 383   OPERATOR_OP (U lhs, enum_flags<enum_type> rhs) = delete;
 384
 385 ENUM_FLAGS_GEN_COMP (operator==, ==)
 386 ENUM_FLAGS_GEN_COMP (operator!=, !=)
 387
 388 /* Unary operators for the raw flags enum.  */
 389
 390 /* We require underlying type to be unsigned when using operator~ --
 391    if it were not unsigned, undefined behavior could result.  However,
 392    asserting this in the class itself would require too many
 393    unnecessary changes to usages of otherwise OK enum types.  */
 394 template <typename enum_type,
 395           typename = is_enum_flags_enum_type_t<enum_type>,
 396           typename
 397             = gdb::Requires<enum_flags_detail::EnumIsUnsigned<enum_type>>>
 398 constexpr enum_type
 399 operator~ (enum_type e)
 400 {
 401   using underlying = typename enum_flags<enum_type>::underlying_type;
 402   return (enum_type) ~underlying (e);
 403 }
 404
 405 template <typename enum_type,
 406           typename = is_enum_flags_enum_type_t<enum_type>,
 407           typename = gdb::Requires<enum_flags_detail::EnumIsSigned<enum_type>>>
 408 constexpr void operator~ (enum_type e) = delete;
 409
 410 template <typename enum_type,
 411           typename = is_enum_flags_enum_type_t<enum_type>,
 412           typename
 413             = gdb::Requires<enum_flags_detail::EnumIsUnsigned<enum_type>>>
 414 constexpr enum_flags<enum_type>
 415 operator~ (enum_flags<enum_type> e)
 416 {
 417   using underlying = typename enum_flags<enum_type>::underlying_type;
 418   return (enum_type) ~underlying (e);
 419 }
 420
 421 template <typename enum_type,
 422           typename = is_enum_flags_enum_type_t<enum_type>,
 423           typename = gdb::Requires<enum_flags_detail::EnumIsSigned<enum_type>>>
 424 constexpr void operator~ (enum_flags<enum_type> e) = delete;
 425
 426 /* Delete operator<< and operator>>.  */
 427
 428 template <typename enum_type, typename any_type,
 429           typename = is_enum_flags_enum_type_t<enum_type>>
 430 void operator<< (const enum_type &, const any_type &) = delete;
 431
 432 template <typename enum_type, typename any_type,
 433           typename = is_enum_flags_enum_type_t<enum_type>>
 434 void operator<< (const enum_flags<enum_type> &, const any_type &) = delete;
 435
 436 template <typename enum_type, typename any_type,
 437           typename = is_enum_flags_enum_type_t<enum_type>>
 438 void operator>> (const enum_type &, const any_type &) = delete;
 439
 440 template <typename enum_type, typename any_type,
 441           typename = is_enum_flags_enum_type_t<enum_type>>
 442 void operator>> (const enum_flags<enum_type> &, const any_type &) = delete;
 443
 444 template<typename E>
 445 template<size_t N>
 446 std::string
 447 enum_flags<E>::to_string (const string_mapping (&mapping)[N]) const
 448 {
 449   enum_type flags = raw ();
 450   std::string res = hex_string (flags);
 451   res += " [";
 452
 453   bool need_space = false;
 454   for (const auto &entry : mapping)
 455     {
 456       if ((flags & entry.flag) != 0)
 457         {
 458           /* Work with an unsigned version of the underlying type,
 459              because if enum_type's underlying type is signed, op~
 460              won't be defined for it, and, bitwise operations on
 461              signed types are implementation defined.  */
 462           using uns = typename std::make_unsigned<underlying_type>::type;
 463           flags &= (enum_type) ~(uns) entry.flag;
 464
 465           if (need_space)
 466             res += " ";
 467           res += entry.str;
 468
 469           need_space = true;
 470         }
 471     }
 472
 473   /* If there were flags not included in the mapping, print them as
 474      a hex number.  */
 475   if (flags != 0)
 476     {
 477       if (need_space)
 478         res += " ";
 479       res += hex_string (flags);
 480     }
 481
 482   res += "]";
 483
 484   return res;
 485 }
 486
 487 #else /* __cplusplus */
 488
 489 /* In C, the flags type is just a typedef for the enum type.  */
 490
 491 #define DEF_ENUM_FLAGS_TYPE(enum_type, flags_type) \
 492   typedef enum_type flags_type
 493
 494 #endif /* __cplusplus */
 495
 496 #endif /* COMMON_ENUM_FLAGS_H */