tdelibs/kdecore/kdemacros.h.in

/* This file is part of the KDE libraries
    Copyright (c) 2002-2003 KDE Team

    This library 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.

    This library 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 this library; see the file COPYING.LIB.  If not, write to
    the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
    Boston, MA 02110-1301, USA.
*/

#ifndef _KDE_MACROS_H_
#define _KDE_MACROS_H_

/* Set by configure */
#undef __KDE_HAVE_GCC_VISIBILITY

/**
 * The KDE_NO_EXPORT macro marks the symbol of the given variable 
 * to be hidden. A hidden symbol is stripped during the linking step, 
 * so it can't be used from outside the resulting library, which is similar
 * to static. However, static limits the visibility to the current 
 * compilation unit. hidden symbols can still be used in multiple compilation
 * units.
 *
 * \code
 * int KDE_NO_EXPORT foo;
 * int KDE_EXPORT bar;
 * \end
 */

#ifdef __KDE_HAVE_GCC_VISIBILITY
#define KDE_NO_EXPORT __attribute__ ((visibility("hidden")))
#define KDE_EXPORT __attribute__ ((visibility("default")))
#elif defined(Q_WS_WIN)
#define KDE_NO_EXPORT
#define KDE_EXPORT __declspec(dllexport)
#else
#define KDE_NO_EXPORT
#define KDE_EXPORT
#endif

/**
 * KDE_Q_EXPORT_PLUGIN is a workaround for Qt not being able to
 * cope with symbol visibility.
 */
#define KDE_Q_EXPORT_PLUGIN(PLUGIN) \
  Q_EXTERN_C KDE_EXPORT const char* qt_ucm_query_verification_data(); \
  Q_EXTERN_C KDE_EXPORT QUnknownInterface* ucm_instantiate(); \
  Q_EXPORT_PLUGIN(PLUGIN)

/**
 * The KDE_PACKED can be used to hint the compiler that a particular
 * structure or class should not contain unnecessary paddings. 
 */

#ifdef __GNUC__
#define KDE_PACKED __attribute__((__packed__))
#else
#define KDE_PACKED
#endif

/**
 * The KDE_DEPRECATED macro can be used to trigger compile-time warnings
 * with newer compilers when deprecated functions are used.
 *
 * For non-inline functions, the macro gets inserted at the very end of the
 * function declaration, right before the semicolon:
 *
 * \code
 * DeprecatedConstructor() KDE_DEPRECATED;
 * void deprecatedFunctionA() KDE_DEPRECATED;
 * int deprecatedFunctionB() const KDE_DEPRECATED;
 * \endcode
 *
 * Functions which are implemented inline are handled differently: for them,
 * the KDE_DEPRECATED macro is inserted at the front, right before the return
 * type, but after "static" or "virtual":
 *
 * \code
 * KDE_DEPRECATED void deprecatedInlineFunctionA() { .. }
 * virtual KDE_DEPRECATED int deprecatedInlineFunctionB() { .. }
 * static KDE_DEPRECATED bool deprecatedInlineFunctionC() { .. }
 * \end
 *
 * You can also mark whole structs or classes as deprecated, by inserting the
 * KDE_DEPRECATED macro after the struct/class keyword, but before the
 * name of the struct/class:
 *
 * \code
 * class KDE_DEPRECATED DeprecatedClass { };
 * struct KDE_DEPRECATED DeprecatedStruct { };
 * \endcode
 *
 * \note
 * It does not make much sense to use the KDE_DEPRECATED keyword for a Qt signal;
 * this is because usually get called by the class which they belong to,
 * and one'd assume that a class author doesn't use deprecated methods of his
 * own class. The only exception to this are signals which are connected to
 * other signals; they get invoked from moc-generated code. In any case, 
 * printing a warning message in either case is not useful.
 * For slots, it can make sense (since slots can be invoked directly) but be
 * aware that if the slots get triggered by a signal, the will get called from
 * moc code as well and thus the warnings are useless.
 *
 * \par
 * Also note that it is not possible to use KDE_DEPRECATED for classes which
 * use the k_dcop keyword (to indicate a DCOP interface declaration); this is
 * because the dcopidl program would choke on the unexpected declaration
 * syntax.
 */

#ifndef KDE_DEPRECATED
#if __GNUC__ - 0 > 3 || (__GNUC__ - 0 == 3 && __GNUC_MINOR__ - 0 >= 2)
  /* gcc >= 3.2 */
# define KDE_DEPRECATED __attribute__ ((deprecated))
#elif defined(_MSC_VER) && (_MSC_VER >= 1300)
  /* msvc >= 7 */
# define KDE_DEPRECATED __declspec(deprecated)
#else
# define KDE_DEPRECATED
#endif
#endif

/**
 * The KDE_ISLIKELY macro tags a boolean expression as likely to evaluate to
 * 'true'. When used in an if ( ) statement, it gives a hint to the compiler
 * that the following codeblock is likely to get executed. Providing this
 * information helps the compiler to optimize the code for better performance.
 * Using the macro has an insignificant code size or runtime memory footprint impact.
 * The code semantics is not affected.
 *
 * \note
 * Providing wrong information ( like marking a condition that almost never
 * passes as 'likely' ) will cause a significant runtime slowdown. Therefore only
 * use it for cases where you can be sure about the odds of the expression to pass
 * in all cases ( independent from e.g. user configuration ).
 *
 * \par
 * The KDE_ISUNLIKELY macro tags an expression as unlikely evaluating to 'true'. 
 *
 * \note
 * Do NOT use ( !KDE_ISLIKELY(foo) ) as an replacement for KDE_ISUNLIKELY !
 *
 * \code
 * if ( KDE_ISUNLIKELY( testsomething() ) )
 *     abort();     // assume its unlikely that the application aborts
 * \endcode
 */
#if __GNUC__ - 0 >= 3
# define KDE_ISLIKELY( x )    __builtin_expect(!!(x),1)
# define KDE_ISUNLIKELY( x )  __builtin_expect(!!(x),0)
#else
# define KDE_ISLIKELY( x )   ( x )
# define KDE_ISUNLIKELY( x )  ( x )
#endif

/**
 * This macro, and it's friends going up to 10 reserve a fixed number of virtual
 * functions in a class.  Because adding virtual functions to a class changes the
 * size of the vtable, adding virtual functions to a class breaks binary
 * compatibility.  However, by using this macro, and decrementing it as new
 * virtual methods are added, binary compatibility can still be preserved.
 *
 * \note The added functions must be added to the header at the same location
 * as the macro; changing the order of virtual functions in a header is also
 * binary incompatible as it breaks the layout of the vtable.
 */

#define RESERVE_VIRTUAL_1 \
    virtual void reservedVirtual1() {}
#define RESERVE_VIRTUAL_2 \
    virtual void reservedVirtual2() {} \
    RESERVE_VIRTUAL_1
#define RESERVE_VIRTUAL_3 \
    virtual void reservedVirtual3() {} \
    RESERVE_VIRTUAL_2
#define RESERVE_VIRTUAL_4 \
    virtual void reservedVirtual4() {} \
    RESERVE_VIRTUAL_3
#define RESERVE_VIRTUAL_5 \
    virtual void reservedVirtual5() {} \
    RESERVE_VIRTUAL_4
#define RESERVE_VIRTUAL_6 \
    virtual void reservedVirtual6() {} \
    RESERVE_VIRTUAL_5
#define RESERVE_VIRTUAL_7 \
    virtual void reservedVirtual7() {} \
    RESERVE_VIRTUAL_6
#define RESERVE_VIRTUAL_8 \
    virtual void reservedVirtual8() {} \
    RESERVE_VIRTUAL_7
#define RESERVE_VIRTUAL_9 \
    virtual void reservedVirtual9() {} \
    RESERVE_VIRTUAL_8
#define RESERVE_VIRTUAL_10 \
    virtual void reservedVirtual10() {} \
    RESERVE_VIRTUAL_9

/**
 * The KDE_WEAK_SYMBOL macro can be used to tell the compiler that
 * a particular function should be a weak symbol (that e.g. may be overriden
 * in another library, -Bdirect will not bind this symbol directly)
 */

#ifdef __GNUC__
#define KDE_WEAK_SYMBOL __attribute__((__weak__))
#else
#define KDE_WEAK_SYMBOL
#endif

#endif /* _KDE_MACROS_H_ */