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 /*----- Miscellaneous utility macros --------------------------------------*/
  36
  37 #define N(v) (sizeof(v)/sizeof(*v))
  38
  39 #define MLIB__STR(x) #x
  40 #define STR(x) MLIB__STR(x)
  41
  42 #define MLIB__GLUE(x, y) x##y
  43 #define GLUE(x, y) MLIB__GLUE(x, y)
  44
  45 /*----- Compiler diagnostics ----------------------------------------------*/
  46
  47 /* --- Compiler-specific definitions --- */
  48
  49 #if defined(__GNUC__)
  50
  51 #  define GCC_VERSION_P(maj, min)                                       \
  52         (__GNUC__ > (maj) || (__GNUC__ == (maj) && __GNUC_MINOR__ >= (min)))
  53
  54 #  if GCC_VERSION_P(2, 5)
  55 #    define NORETURN __attribute__((noreturn))
  56 #    define PRINTF_LIKE(fix, aix) __attribute__((format(printf, fix, aix)))
  57 #    define SCANF_LIKE(fix, aix) __attribute__((format(scanf, fix, aix)))
  58 #    define IGNORABLE __attribute__((unused))
  59 #  endif
  60
  61 #  if GCC_VERSION_P(4, 5)
  62 #    define DEPRECATED(msg) __attribute__((deprecated(msg)))
  63 #  elif GCC_VERSION_P(3, 1)
  64 #    define DEPRECATED(msg) __attribute__((deprecated))
  65 #  endif
  66
  67 #  if GCC_VERSION_P(4, 0)
  68 #    define EXECL_LIKE(ntrail) __attribute__((sentinel(ntrail)))
  69 #  endif
  70
  71 #  if GCC_VERSION_P(4, 6)
  72
  73      /* --- Diagnostic suppression in GCC: a tale of woe --- *
  74       *
  75       * This is extremely unpleasant, largely as a result of bugs in the GCC
  76       * preprocessor's handling of @_Pragma@.  The fundamental problem is
  77       * that it's the preprocessor, and not the compiler proper, which
  78       * detects @_Pragma@, emitting @#pragma@ lines into its output; and it
  79       * does it during macro expansion, even if the macro is being expanded
  80       * during argument collection.  Since arguments are expanded before
  81       * replacing the macro's invocation with its body, a pragma in an
  82       * argument will be emitted %%\emph{before}%% any pragmata in the body,
  83       * even if they appear before the argument in the body -- and even if
  84       * the argument doesn't actually appear anywhere at all in the body.
  85       *
  86       * Another, rather less significant, problem is that @_Pragma@'s
  87       * argument is a single string literal, recognized in translation phase
  88       * 4, before string-literal concatenation in phase 6, so we must build
  89       * pragma bodies as token lists and then stringify them.
  90       *
  91       * As a result, we need some subterfuge here.  The @MLIB__PRAGMA_HACK@
  92       * macro issues a @_Pragma@ on its argument token list, which it
  93       * stringifies; this deals with the second problem.  The first is
  94       * trickier: we must delay expansion of @MLIB__PRAGMA_HACK@ from the
  95       * argument collection phase to the body rescanning phase, and we do
  96       * this by splitting the invocations between @GCC_WARNING@ macro calls:
  97       * the name is left hanging from the previous call (or from
  98       * @MLIB__MUFFLE_WARNINGS@, in the first case) and the body is supplied
  99       * by @GCC_WARNING@, which also supplies the next @MLIB__PRAGMA_HACK@.
 100       * The remaining problem is to make sure we can dispose of the final
 101       * trailing @MLIB__PRAGMA_HACK@ harmlessly, which we do by introducing
 102       * an extra argument @emitp@, which may be either @t@ or @nil@; this
 103       * dispatches to an appropriate helper macro by means of token-pasting.
 104       *
 105       * I'm so sorry.
 106       */
 107
 108 #    define MLIB__PRAGMA_HACK_t(x) _Pragma(#x)
 109 #    define MLIB__PRAGMA_HACK_nil(x)
 110 #    define MLIB__PRAGMA_HACK(emitp, x) MLIB__PRAGMA_HACK_##emitp(x)
 111 #    define MLIB__MUFFLE_WARNINGS(warns, body)                          \
 112         _Pragma("GCC diagnostic push") MLIB__PRAGMA_HACK                \
 113         warns                                                           \
 114         (nil, nil)                                                      \
 115         body                                                            \
 116         _Pragma("GCC diagnostic pop")
 117 #    define GCC_WARNING(warn)                                           \
 118         (t, GCC diagnostic ignored warn) MLIB__PRAGMA_HACK
 119 #    define MUFFLE_WARNINGS_DECL(warns, body)                           \
 120         MLIB__MUFFLE_WARNINGS(warns, body)
 121 #    define MUFFLE_WARNINGS_EXPR(warns, body)                           \
 122         __extension__ ({ MLIB__MUFFLE_WARNINGS(warns, (body);) })
 123 #    define MUFFLE_WARNINGS_STMT(warns, body)                           \
 124         do { MLIB__MUFFLE_WARNINGS(warns, body) } while (0)
 125 #  endif
 126
 127 #endif
 128
 129 /* --- Fallback definitions, mostly trivial --- */
 130
 131 #ifndef GCC_VERSION_P
 132 #  define GCC_VERSION_P(maj, min) 0
 133 #endif
 134
 135 #ifndef DEPRECATED
 136 #  define DEPRECATED(msg)
 137 #endif
 138
 139 #ifndef EXECL_LIKE
 140 #  define EXECL_LIKE(ntrail)
 141 #endif
 142
 143 #ifndef DISCARD
 144 #  define DISCARD(x) do if (x); while (0)
 145 #endif
 146
 147 #ifndef IGNORE
 148 #  define IGNORE(x) ((void)(x))
 149 #endif
 150
 151 #ifndef MUFFLE_WARNINGS_DECL
 152 #  define MUFFLE_WARNINGS_DECL(warns, body) body
 153 #endif
 154
 155 #ifndef MUFFLE_WARNINGS_EXPR
 156 #  define MUFFLE_WARNINGS_EXPR(warns, body) (body)
 157 #endif
 158
 159 #ifndef MUFFLE_WARNINGS_STMT
 160 #  define MUFFLE_WARNINGS_STMT(warns, body) do { body } while (0)
 161 #endif
 162
 163 #ifndef PRINTF_LIKE
 164 #  define PRINF_LIKE(fmtix, argix)
 165 #endif
 166
 167 #ifndef SCANF_LIKE
 168 #  define SCANF_LIKE(fmtix, argix)
 169 #endif
 170
 171 #ifndef IGNORABLE
 172 #  define IGNORABLE
 173 #endif
 174
 175 #ifndef GCC_WARNING
 176 #  define GCC_WARNING(warn)
 177 #endif
 178
 179 /*----- That's all, folks -------------------------------------------------*/
 180
 181 #ifdef __cplusplus
 182   }
 183 #endif
 184
 185 #endif