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