lib/attribute.h

   1 /* ATTRIBUTE_* macros for using attributes in GCC and similar compilers
   2
   3    Copyright 2020 Free Software Foundation, Inc.
   4
   5    This program is free software: you can redistribute it and/or modify it
   6    under the terms of the GNU Lesser General Public License as published
   7    by 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 GNU
  13    Lesser General Public License for more details.
  14
  15    You should have received a copy of the GNU Lesser General Public License
  16    along with this program.  If not, see <https://www.gnu.org/licenses/>.  */
  17
  18 /* Written by Paul Eggert.  */
  19
  20 /* Provide public ATTRIBUTE_* names for the private _GL_ATTRIBUTE_*
  21    macros used within Gnulib.  */
  22
  23 /* These attributes can be placed in two ways:
  24      - At the start of a declaration (i.e. even before storage-class
  25        specifiers!); then they apply to all entities that are declared
  26        by the declaration.
  27      - Immediately after the name of an entity being declared by the
  28        declaration; then they apply to that entity only.  */
  29
  30 #ifndef _GL_ATTRIBUTE_H
  31 #define _GL_ATTRIBUTE_H
  32
  33
  34 /* This file defines two types of attributes:
  35    * C2X standard attributes.  These have macro names that do not begin with
  36      'ATTRIBUTE_'.
  37    * Selected GCC attributes; see:
  38      https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html
  39      https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html
  40      https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html
  41      These names begin with 'ATTRIBUTE_' to avoid name clashes.  */
  42
  43
  44 /* =============== Attributes for specific kinds of functions =============== */
  45
  46 /* Attributes for functions that should not be used.  */
  47
  48 /* Warn if the entity is used.  */
  49 /* Applies to:
  50      - function, variable,
  51      - struct, union, struct/union member,
  52      - enumeration, enumeration item,
  53      - typedef,
  54    in C++ also: namespace, class, template specialization.  */
  55 #define DEPRECATED _GL_ATTRIBUTE_DEPRECATED
  56
  57 /* If a function call is not optimized way, warn with MSG.  */
  58 /* Applies to: functions.  */
  59 #define ATTRIBUTE_WARNING(msg) _GL_ATTRIBUTE_WARNING (msg)
  60
  61 /* If a function call is not optimized way, report an error with MSG.  */
  62 /* Applies to: functions.  */
  63 #define ATTRIBUTE_ERROR(msg) _GL_ATTRIBUTE_ERROR (msg)
  64
  65
  66 /* Attributes for memory-allocating functions.  */
  67
  68 /* The function returns a pointer to freshly allocated memory.  */
  69 /* Applies to: functions.  */
  70 #define ATTRIBUTE_MALLOC _GL_ATTRIBUTE_MALLOC
  71
  72 /* ATTRIBUTE_ALLOC_SIZE ((N)) - The Nth argument of the function
  73    is the size of the returned memory block.
  74    ATTRIBUTE_ALLOC_SIZE ((M, N)) - Multiply the Mth and Nth arguments
  75    to determine the size of the returned memory block.  */
  76 /* Applies to: function, pointer to function, function types.  */
  77 #define ATTRIBUTE_ALLOC_SIZE(args) _GL_ATTRIBUTE_ALLOC_SIZE (args)
  78
  79
  80 /* Attributes for variadic functions.  */
  81
  82 /* The variadic function expects a trailing NULL argument.
  83    ATTRIBUTE_SENTINEL () - The last argument is NULL (requires C99).
  84    ATTRIBUTE_SENTINEL ((N)) - The (N+1)st argument from the end is NULL.  */
  85 /* Applies to: functions.  */
  86 #define ATTRIBUTE_SENTINEL(pos) _GL_ATTRIBUTE_SENTINEL (pos)
  87
  88
  89 /* ================== Attributes for compiler diagnostics ================== */
  90
  91 /* Attributes that help the compiler diagnose programmer mistakes.
  92    Some of them may also help for some compiler optimizations.  */
  93
  94 /* ATTRIBUTE_FORMAT ((ARCHETYPE, STRING-INDEX, FIRST-TO-CHECK)) -
  95    The STRING-INDEXth function argument is a format string of style
  96    ARCHETYPE, which is one of:
  97      printf, gnu_printf
  98      scanf, gnu_scanf,
  99      strftime, gnu_strftime,
 100      strfmon,
 101    or the same thing prefixed and suffixed with '__'.
 102    If FIRST-TO-CHECK is not 0, arguments starting at FIRST-TO_CHECK
 103    are suitable for the format string.  */
 104 /* Applies to: functions.  */
 105 #define ATTRIBUTE_FORMAT(spec) _GL_ATTRIBUTE_FORMAT (spec)
 106
 107 /* ATTRIBUTE_NONNULL ((N1, N2,...)) - Arguments N1, N2,... must not be NULL.
 108    ATTRIBUTE_NONNULL () - All pointer arguments must not be null.  */
 109 /* Applies to: functions.  */
 110 #define ATTRIBUTE_NONNULL(args) _GL_ATTRIBUTE_NONNULL (args)
 111
 112 /* The function's return value is a non-NULL pointer.  */
 113 /* Applies to: functions.  */
 114 #define ATTRIBUTE_RETURNS_NONNULL _GL_ATTRIBUTE_RETURNS_NONNULL
 115
 116 /* Warn if the caller does not use the return value,
 117    unless the caller uses something like ignore_value.  */
 118 /* Applies to: function, enumeration, class.  */
 119 #define NODISCARD _GL_ATTRIBUTE_NODISCARD
 120
 121
 122 /* Attributes that disable false alarms when the compiler diagnoses
 123    programmer "mistakes".  */
 124
 125 /* Do not warn if the entity is not used.  */
 126 /* Applies to:
 127      - function, variable,
 128      - struct, union, struct/union member,
 129      - enumeration, enumeration item,
 130      - typedef,
 131    in C++ also: class.  */
 132 #define MAYBE_UNUSED _GL_ATTRIBUTE_MAYBE_UNUSED
 133
 134 /* The contents of a character array is not meant to be NUL-terminated.  */
 135 /* Applies to: struct/union members and variables that are arrays of element
 136    type '[[un]signed] char'.  */
 137 #define ATTRIBUTE_NONSTRING _GL_ATTRIBUTE_NONSTRING
 138
 139 /* Do not warn if control flow falls through to the immediately
 140    following 'case' or 'default' label.  */
 141 /* Applies to: Empty statement (;), inside a 'switch' statement.  */
 142 #define FALLTHROUGH _GL_ATTRIBUTE_FALLTHROUGH
 143
 144
 145 /* ================== Attributes for debugging information ================== */
 146
 147 /* Attributes regarding debugging information emitted by the compiler.  */
 148
 149 /* Omit the function from stack traces when debugging.  */
 150 /* Applies to: function.  */
 151 #define ATTRIBUTE_ARTIFICIAL _GL_ATTRIBUTE_ARTIFICIAL
 152
 153 /* Make the entity visible to debuggers etc., even with '-fwhole-program'.  */
 154 /* Applies to: functions, variables.  */
 155 #define ATTRIBUTE_EXTERNALLY_VISIBLE _GL_ATTRIBUTE_EXTERNALLY_VISIBLE
 156
 157
 158 /* ========== Attributes that mainly direct compiler optimizations ========== */
 159
 160 /* The function does not throw exceptions.  */
 161 /* Applies to: functions.  */
 162 #define ATTRIBUTE_NOTHROW _GL_ATTRIBUTE_NOTHROW
 163
 164 /* Do not inline the function.  */
 165 /* Applies to: functions.  */
 166 #define ATTRIBUTE_NOINLINE _GL_ATTRIBUTE_NOINLINE
 167
 168 /* Always inline the function, and report an error if the compiler
 169    cannot inline.  */
 170 /* Applies to: function.  */
 171 #define ATTRIBUTE_ALWAYS_INLINE _GL_ATTRIBUTE_ALWAYS_INLINE
 172
 173 /* It is OK for a compiler to omit duplicate calls with the same arguments.
 174    This attribute is safe for a function that neither depends on
 175    nor affects observable state, and always returns exactly once -
 176    e.g., does not loop forever, and does not call longjmp.
 177    (This attribute is stricter than ATTRIBUTE_PURE.)  */
 178 /* Applies to: functions.  */
 179 #define ATTRIBUTE_CONST _GL_ATTRIBUTE_CONST
 180
 181 /* It is OK for a compiler to omit duplicate calls with the same
 182    arguments if observable state is not changed between calls.
 183    This attribute is safe for a function that does not affect
 184    observable state, and always returns exactly once.
 185    (This attribute is looser than ATTRIBUTE_CONST.)  */
 186 /* Applies to: functions.  */
 187 #define ATTRIBUTE_PURE _GL_ATTRIBUTE_PURE
 188
 189 /* The function is rarely executed.  */
 190 /* Applies to: functions.  */
 191 #define ATTRIBUTE_COLD _GL_ATTRIBUTE_COLD
 192
 193 /* If called from some other compilation unit, the function executes
 194    code from that unit only by return or by exception handling,
 195    letting the compiler optimize that unit more aggressively.  */
 196 /* Applies to: functions.  */
 197 #define ATTRIBUTE_LEAF _GL_ATTRIBUTE_LEAF
 198
 199 /* For struct members: The member has the smallest possible alignment.
 200    For struct, union, class: All members have the smallest possible alignment,
 201    minimizing the memory required.  */
 202 /* Applies to: struct members, struct, union,
 203    in C++ also: class.  */
 204 #define ATTRIBUTE_PACKED _GL_ATTRIBUTE_PACKED
 205
 206
 207 /* ================ Attributes that make invalid code valid ================ */
 208
 209 /* Attributes that prevent fatal compiler optimizations for code that is not
 210    fully ISO C compliant.  */
 211
 212 /* Pointers to the type may point to the same storage as pointers to
 213    other types, thus disabling strict aliasing optimization.  */
 214 /* Applies to: types.  */
 215 #define ATTRIBUTE_MAY_ALIAS _GL_ATTRIBUTE_MAY_ALIAS
 216
 217
 218 #endif /* _GL_ATTRIBUTE_H */