mdw@git.distorted.org.uk Git - mLib/blob - utils/macros.h

   1 /* -*-c-*-
   2  *
   3  * Handy macros
   4  *
   5  * (c) 2003 Straylight/Edgeware
   6  */
   7
   8 /*----- Licensing notice --------------------------------------------------*
   9  *
  10  * This file is part of the mLib utilities library.
  11  *
  12  * mLib is free software; you can redistribute it and/or modify
  13  * it under the terms of the GNU Library General Public License as
  14  * published by the Free Software Foundation; either version 2 of the
  15  * License, or (at your option) any later version.
  16  *
  17  * mLib is distributed in the hope that it will be useful,
  18  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  19  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  20  * GNU Library General Public License for more details.
  21  *
  22  * You should have received a copy of the GNU Library General Public
  23  * License along with mLib; if not, write to the Free
  24  * Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
  25  * MA 02111-1307, USA.
  26  */
  27
  28 #ifndef MLIB_MACROS_H
  29 #define MLIB_MACROS_H
  30
  31 #ifdef __cplusplus
  32   extern "C" {
  33 #endif
  34
  35 /*----- Header files ------------------------------------------------------*/
  36
  37 #ifndef MLIB_COMPILER_H
  38 #  include "compiler.h"
  39 #endif
  40
  41 /*----- Miscellaneous utility macros --------------------------------------*/
  42
  43 #define N(v) (sizeof(v)/sizeof(*(v)))
  44
  45 #define MLIB__STR(x) #x
  46 #define STR(x) MLIB__STR(x)
  47
  48 #define MLIB__GLUE(x, y) x##y
  49 #define GLUE(x, y) MLIB__GLUE(x, y)
  50
  51 /*----- Compiler diagnostics ----------------------------------------------*/
  52
  53 /* --- Compiler-specific definitions --- */
  54
  55 #if GCC_VERSION_P(2, 5) || CLANG_VERSION_P(3, 3)
  56 #  define NORETURN __attribute__((noreturn))
  57 #  define PRINTF_LIKE(fix, aix) __attribute__((format(printf, fix, aix)))
  58 #  define SCANF_LIKE(fix, aix) __attribute__((format(scanf, fix, aix)))
  59 #  define IGNORABLE __attribute__((unused))
  60 #endif
  61
  62 #if GCC_VERSION_P(4, 5) || CLANG_VERSION_P(3, 3)
  63 #  define DEPRECATED(msg) __attribute__((deprecated(msg)))
  64 #elif GCC_VERSION_P(3, 1)
  65 #  define DEPRECATED(msg) __attribute__((deprecated))
  66 #endif
  67
  68 #if GCC_VERSION_P(4, 0) || CLANG_VERSION_P(3, 3)
  69 #  define EXECL_LIKE(ntrail) __attribute__((sentinel(ntrail)))
  70 #endif
  71
  72 #if CLANG_VERSION_P(3, 3)
  73
  74 #  define MLIB__PRAGMA_HACK(x) _Pragma(#x)
  75 #  define MLIB__MUFFLE_WARNINGS(warns, body)                            \
  76         _Pragma("clang diagnostic push")                                \
  77         warns                                                           \
  78         body                                                            \
  79         _Pragma("clang diagnostic pop")
  80 #  define CLANG_WARNING(warn)                                           \
  81         MLIB__PRAGMA_HACK(clang diagnostic ignored warn)
  82 #  define MUFFLE_WARNINGS_DECL(warns, body)                             \
  83         MLIB__MUFFLE_WARNINGS(warns, body)
  84 #  define MUFFLE_WARNINGS_EXPR(warns, body)                             \
  85         __extension__ ({ MLIB__MUFFLE_WARNINGS(warns, (body);) })
  86 #  define MUFFLE_WARNINGS_STMT(warns, body)                             \
  87         do { MLIB__MUFFLE_WARNINGS(warns, body) } while (0)
  88
  89 #elif GCC_VERSION_P(4, 6)
  90
  91    /* --- Diagnostic suppression in GCC: a tale of woe --- *
  92     *
  93     * This is extremely unpleasant, largely as a result of bugs in the GCC
  94     * preprocessor's handling of @_Pragma@.  The fundamental problem is
  95     * that it's the preprocessor, and not the compiler proper, which
  96     * detects @_Pragma@, emitting @#pragma@ lines into its output; and it
  97     * does it during macro expansion, even if the macro is being expanded
  98     * during argument collection.  Since arguments are expanded before
  99     * replacing the macro's invocation with its body, a pragma in an
 100     * argument will be emitted %%\emph{before}%% any pragmata in the body,
 101     * even if they appear before the argument in the body -- and even if
 102     * the argument doesn't actually appear anywhere at all in the body.
 103     *
 104     * Another, rather less significant, problem is that @_Pragma@'s
 105     * argument is a single string literal, recognized in translation phase
 106     * 4, before string-literal concatenation in phase 6, so we must build
 107     * pragma bodies as token lists and then stringify them.
 108     *
 109     * As a result, we need some subterfuge here.  The @MLIB__PRAGMA_HACK@
 110     * macro issues a @_Pragma@ on its argument token list, which it
 111     * stringifies; this deals with the second problem.  The first is
 112     * trickier: we must delay expansion of @MLIB__PRAGMA_HACK@ from the
 113     * argument collection phase to the body rescanning phase, and we do
 114     * this by splitting the invocations between @GCC_WARNING@ macro calls:
 115     * the name is left hanging from the previous call (or from
 116     * @MLIB__MUFFLE_WARNINGS@, in the first case) and the body is supplied
 117     * by @GCC_WARNING@, which also supplies the next @MLIB__PRAGMA_HACK@.
 118     * The remaining problem is to make sure we can dispose of the final
 119     * trailing @MLIB__PRAGMA_HACK@ harmlessly, which we do by introducing
 120     * an extra argument @emitp@, which may be either @t@ or @nil@; this
 121     * dispatches to an appropriate helper macro by means of token-pasting.
 122     *
 123     * I'm so sorry.
 124     */
 125
 126 #  define MLIB__PRAGMA_HACK_t(x) _Pragma(#x)
 127 #  define MLIB__PRAGMA_HACK_nil(x)
 128 #  define MLIB__PRAGMA_HACK(emitp, x) MLIB__PRAGMA_HACK_##emitp(x)
 129 #  define MLIB__MUFFLE_WARNINGS(warns, body)                            \
 130         _Pragma("GCC diagnostic push") MLIB__PRAGMA_HACK                \
 131         warns                                                           \
 132         (nil, nil)                                                      \
 133         body                                                            \
 134         _Pragma("GCC diagnostic pop")
 135 #  define GCC_WARNING(warn)                                             \
 136         (t, GCC diagnostic ignored warn) MLIB__PRAGMA_HACK
 137 #  define MUFFLE_WARNINGS_DECL(warns, body)                             \
 138         MLIB__MUFFLE_WARNINGS(warns, body)
 139 #  define MUFFLE_WARNINGS_EXPR(warns, body)                             \
 140         __extension__ ({ MLIB__MUFFLE_WARNINGS(warns, (body);) })
 141 #  define MUFFLE_WARNINGS_STMT(warns, body)                             \
 142         do { MLIB__MUFFLE_WARNINGS(warns, body) } while (0)
 143 #endif
 144
 145 /* --- Fallback definitions, mostly trivial --- */
 146
 147 #ifndef DEPRECATED
 148 #  define DEPRECATED(msg)
 149 #endif
 150
 151 #ifndef EXECL_LIKE
 152 #  define EXECL_LIKE(ntrail)
 153 #endif
 154
 155 #ifndef DISCARD
 156 #  define DISCARD(x) do if (x); while (0)
 157 #endif
 158
 159 #ifndef IGNORE
 160 #  define IGNORE(x) ((void)(x))
 161 #endif
 162
 163 #ifndef MUFFLE_WARNINGS_DECL
 164 #  define MUFFLE_WARNINGS_DECL(warns, body) body
 165 #endif
 166
 167 #ifndef MUFFLE_WARNINGS_EXPR
 168 #  define MUFFLE_WARNINGS_EXPR(warns, body) (body)
 169 #endif
 170
 171 #ifndef MUFFLE_WARNINGS_STMT
 172 #  define MUFFLE_WARNINGS_STMT(warns, body) do { body } while (0)
 173 #endif
 174
 175 #ifndef PRINTF_LIKE
 176 #  define PRINF_LIKE(fmtix, argix)
 177 #endif
 178
 179 #ifndef SCANF_LIKE
 180 #  define SCANF_LIKE(fmtix, argix)
 181 #endif
 182
 183 #ifndef NORETURN
 184 #  define NORETURN
 185 #endif
 186
 187 #ifndef IGNORABLE
 188 #  define IGNORABLE
 189 #endif
 190
 191 #ifndef GCC_WARNING
 192 #  define GCC_WARNING(warn)
 193 #endif
 194
 195 #ifndef CLANG_WARNING
 196 #  define CLANG_WARNING(warn)
 197 #endif
 198
 199 /*----- That's all, folks -------------------------------------------------*/
 200
 201 #ifdef __cplusplus
 202   }
 203 #endif
 204
 205 #endif