utils/macros.h: Refactor the GCC-ish compiler support.

[mLib] / utils / macros.h

/* -*-c-*-
 *
 * Handy macros
 *
 * (c) 2003 Straylight/Edgeware
 */

/*----- Licensing notice --------------------------------------------------*
 *
 * This file is part of the mLib utilities library.
 *
 * mLib is free software; you can redistribute it and/or modify
 * it under the terms of the GNU Library General Public License as
 * published by the Free Software Foundation; either version 2 of the
 * License, or (at your option) any later version.
 *
 * mLib is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU Library General Public License for more details.
 *
 * You should have received a copy of the GNU Library General Public
 * License along with mLib; if not, write to the Free
 * Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
 * MA 02111-1307, USA.
 */

#ifndef MLIB_MACROS_H
#define MLIB_MACROS_H

#ifdef __cplusplus
  extern "C" {
#endif

/*----- Miscellaneous utility macros --------------------------------------*/

#define N(v) (sizeof(v)/sizeof(*v))

#define MLIB__STR(x) #x
#define STR(x) MLIB__STR(x)

#define MLIB__GLUE(x, y) x##y
#define GLUE(x, y) MLIB__GLUE(x, y)

/*----- Compiler diagnostics ----------------------------------------------*/

/* --- Compiler-specific definitions --- */

#if defined(__GNUC__)
#  define GCC_VERSION_P(maj, min)					\
	(__GNUC__ > (maj) || (__GNUC__ == (maj) && __GNUC_MINOR__ >= (min)))
#else
#  define GCC_VERSION_P(maj, min) 0
#endif

#if GCC_VERSION_P(2, 5)
#  define NORETURN __attribute__((noreturn))
#  define PRINTF_LIKE(fix, aix) __attribute__((format(printf, fix, aix)))
#  define SCANF_LIKE(fix, aix) __attribute__((format(scanf, fix, aix)))
#  define IGNORABLE __attribute__((unused))
#endif

#if GCC_VERSION_P(4, 5)
#  define DEPRECATED(msg) __attribute__((deprecated(msg)))
#elif GCC_VERSION_P(3, 1)
#  define DEPRECATED(msg) __attribute__((deprecated))
#endif

#if GCC_VERSION_P(4, 0)
#  define EXECL_LIKE(ntrail) __attribute__((sentinel(ntrail)))
#endif

#if GCC_VERSION_P(4, 6)

   /* --- Diagnostic suppression in GCC: a tale of woe --- *
    *
    * This is extremely unpleasant, largely as a result of bugs in the GCC
    * preprocessor's handling of @_Pragma@.  The fundamental problem is
    * that it's the preprocessor, and not the compiler proper, which
    * detects @_Pragma@, emitting @#pragma@ lines into its output; and it
    * does it during macro expansion, even if the macro is being expanded
    * during argument collection.  Since arguments are expanded before
    * replacing the macro's invocation with its body, a pragma in an
    * argument will be emitted %%\emph{before}%% any pragmata in the body,
    * even if they appear before the argument in the body -- and even if
    * the argument doesn't actually appear anywhere at all in the body.
    *
    * Another, rather less significant, problem is that @_Pragma@'s
    * argument is a single string literal, recognized in translation phase
    * 4, before string-literal concatenation in phase 6, so we must build
    * pragma bodies as token lists and then stringify them.
    *
    * As a result, we need some subterfuge here.  The @MLIB__PRAGMA_HACK@
    * macro issues a @_Pragma@ on its argument token list, which it
    * stringifies; this deals with the second problem.  The first is
    * trickier: we must delay expansion of @MLIB__PRAGMA_HACK@ from the
    * argument collection phase to the body rescanning phase, and we do
    * this by splitting the invocations between @GCC_WARNING@ macro calls:
    * the name is left hanging from the previous call (or from
    * @MLIB__MUFFLE_WARNINGS@, in the first case) and the body is supplied
    * by @GCC_WARNING@, which also supplies the next @MLIB__PRAGMA_HACK@.
    * The remaining problem is to make sure we can dispose of the final
    * trailing @MLIB__PRAGMA_HACK@ harmlessly, which we do by introducing
    * an extra argument @emitp@, which may be either @t@ or @nil@; this
    * dispatches to an appropriate helper macro by means of token-pasting.
    *
    * I'm so sorry.
    */

#  define MLIB__PRAGMA_HACK_t(x) _Pragma(#x)
#  define MLIB__PRAGMA_HACK_nil(x)
#  define MLIB__PRAGMA_HACK(emitp, x) MLIB__PRAGMA_HACK_##emitp(x)
#  define MLIB__MUFFLE_WARNINGS(warns, body)				\
	_Pragma("GCC diagnostic push") MLIB__PRAGMA_HACK		\
	warns								\
	(nil, nil)							\
	body								\
	_Pragma("GCC diagnostic pop")
#  define GCC_WARNING(warn)						\
	(t, GCC diagnostic ignored warn) MLIB__PRAGMA_HACK
#  define MUFFLE_WARNINGS_DECL(warns, body)				\
	MLIB__MUFFLE_WARNINGS(warns, body)
#  define MUFFLE_WARNINGS_EXPR(warns, body)				\
	__extension__ ({ MLIB__MUFFLE_WARNINGS(warns, (body);) })
#  define MUFFLE_WARNINGS_STMT(warns, body)				\
	do { MLIB__MUFFLE_WARNINGS(warns, body) } while (0)
#endif

/* --- Fallback definitions, mostly trivial --- */

#ifndef DEPRECATED
#  define DEPRECATED(msg)
#endif

#ifndef EXECL_LIKE
#  define EXECL_LIKE(ntrail)
#endif

#ifndef DISCARD
#  define DISCARD(x) do if (x); while (0)
#endif

#ifndef IGNORE
#  define IGNORE(x) ((void)(x))
#endif

#ifndef MUFFLE_WARNINGS_DECL
#  define MUFFLE_WARNINGS_DECL(warns, body) body
#endif

#ifndef MUFFLE_WARNINGS_EXPR
#  define MUFFLE_WARNINGS_EXPR(warns, body) (body)
#endif

#ifndef MUFFLE_WARNINGS_STMT
#  define MUFFLE_WARNINGS_STMT(warns, body) do { body } while (0)
#endif

#ifndef PRINTF_LIKE
#  define PRINF_LIKE(fmtix, argix)
#endif

#ifndef SCANF_LIKE
#  define SCANF_LIKE(fmtix, argix)
#endif

#ifndef IGNORABLE
#  define IGNORABLE
#endif

#ifndef GCC_WARNING
#  define GCC_WARNING(warn)
#endif

/*----- That's all, folks -------------------------------------------------*/

#ifdef __cplusplus
  }
#endif

#endif