emacs/c++defs.h

/* C++ compatible function declaration macros.
   Copyright (C) 2010-2011 Free Software Foundation, Inc.

   This program is free software: you can redistribute it and/or modify it
   under the terms of the GNU General Public License as published
   by the Free Software Foundation; either version 3 of the License, or
   (at your option) any later version.

   This program 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
   General Public License for more details.

   You should have received a copy of the GNU General Public License
   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */

#ifndef _GL_CXXDEFS_H
#define _GL_CXXDEFS_H

/* The three most frequent use cases of these macros are:

   * For providing a substitute for a function that is missing on some
     platforms, but is declared and works fine on the platforms on which
     it exists:

       #if @GNULIB_FOO@
       # if !@HAVE_FOO@
       _GL_FUNCDECL_SYS (foo, ...);
       # endif
       _GL_CXXALIAS_SYS (foo, ...);
       _GL_CXXALIASWARN (foo);
       #elif defined GNULIB_POSIXCHECK
       ...
       #endif

   * For providing a replacement for a function that exists on all platforms,
     but is broken/insufficient and needs to be replaced on some platforms:

       #if @GNULIB_FOO@
       # if @REPLACE_FOO@
       #  if !(defined __cplusplus && defined GNULIB_NAMESPACE)
       #   undef foo
       #   define foo rpl_foo
       #  endif
       _GL_FUNCDECL_RPL (foo, ...);
       _GL_CXXALIAS_RPL (foo, ...);
       # else
       _GL_CXXALIAS_SYS (foo, ...);
       # endif
       _GL_CXXALIASWARN (foo);
       #elif defined GNULIB_POSIXCHECK
       ...
       #endif

   * For providing a replacement for a function that exists on some platforms
     but is broken/insufficient and needs to be replaced on some of them and
     is additionally either missing or undeclared on some other platforms:

       #if @GNULIB_FOO@
       # if @REPLACE_FOO@
       #  if !(defined __cplusplus && defined GNULIB_NAMESPACE)
       #   undef foo
       #   define foo rpl_foo
       #  endif
       _GL_FUNCDECL_RPL (foo, ...);
       _GL_CXXALIAS_RPL (foo, ...);
       # else
       #  if !@HAVE_FOO@   or   if !@HAVE_DECL_FOO@
       _GL_FUNCDECL_SYS (foo, ...);
       #  endif
       _GL_CXXALIAS_SYS (foo, ...);
       # endif
       _GL_CXXALIASWARN (foo);
       #elif defined GNULIB_POSIXCHECK
       ...
       #endif
*/

/* _GL_EXTERN_C declaration;
   performs the declaration with C linkage.  */
#if defined __cplusplus
# define _GL_EXTERN_C extern "C"
#else
# define _GL_EXTERN_C extern
#endif

/* _GL_FUNCDECL_RPL (func, rettype, parameters_and_attributes);
   declares a replacement function, named rpl_func, with the given prototype,
   consisting of return type, parameters, and attributes.
   Example:
     _GL_FUNCDECL_RPL (open, int, (const char *filename, int flags, ...)
                                  _GL_ARG_NONNULL ((1)));
 */
#define _GL_FUNCDECL_RPL(func,rettype,parameters_and_attributes) \
  _GL_FUNCDECL_RPL_1 (rpl_##func, rettype, parameters_and_attributes)
#define _GL_FUNCDECL_RPL_1(rpl_func,rettype,parameters_and_attributes) \
  _GL_EXTERN_C rettype rpl_func parameters_and_attributes

/* _GL_FUNCDECL_SYS (func, rettype, parameters_and_attributes);
   declares the system function, named func, with the given prototype,
   consisting of return type, parameters, and attributes.
   Example:
     _GL_FUNCDECL_SYS (open, int, (const char *filename, int flags, ...)
                                  _GL_ARG_NONNULL ((1)));
 */
#define _GL_FUNCDECL_SYS(func,rettype,parameters_and_attributes) \
  _GL_EXTERN_C rettype func parameters_and_attributes

/* _GL_CXXALIAS_RPL (func, rettype, parameters);
   declares a C++ alias called GNULIB_NAMESPACE::func
   that redirects to rpl_func, if GNULIB_NAMESPACE is defined.
   Example:
     _GL_CXXALIAS_RPL (open, int, (const char *filename, int flags, ...));
 */
#define _GL_CXXALIAS_RPL(func,rettype,parameters) \
  _GL_CXXALIAS_RPL_1 (func, rpl_##func, rettype, parameters)
#if defined __cplusplus && defined GNULIB_NAMESPACE
# define _GL_CXXALIAS_RPL_1(func,rpl_func,rettype,parameters) \
    namespace GNULIB_NAMESPACE                                \
    {                                                         \
      rettype (*const func) parameters = ::rpl_func;          \
    }                                                         \
    _GL_EXTERN_C int _gl_cxxalias_dummy
#else
# define _GL_CXXALIAS_RPL_1(func,rpl_func,rettype,parameters) \
    _GL_EXTERN_C int _gl_cxxalias_dummy
#endif

/* _GL_CXXALIAS_RPL_CAST_1 (func, rpl_func, rettype, parameters);
   is like  _GL_CXXALIAS_RPL_1 (func, rpl_func, rettype, parameters);
   except that the C function rpl_func may have a slightly different
   declaration.  A cast is used to silence the "invalid conversion" error
   that would otherwise occur.  */
#if defined __cplusplus && defined GNULIB_NAMESPACE
# define _GL_CXXALIAS_RPL_CAST_1(func,rpl_func,rettype,parameters) \
    namespace GNULIB_NAMESPACE                                     \
    {                                                              \
      rettype (*const func) parameters =                           \
        reinterpret_cast<rettype(*)parameters>(::rpl_func);        \
    }                                                              \
    _GL_EXTERN_C int _gl_cxxalias_dummy
#else
# define _GL_CXXALIAS_RPL_CAST_1(func,rpl_func,rettype,parameters) \
    _GL_EXTERN_C int _gl_cxxalias_dummy
#endif

/* _GL_CXXALIAS_SYS (func, rettype, parameters);
   declares a C++ alias called GNULIB_NAMESPACE::func
   that redirects to the system provided function func, if GNULIB_NAMESPACE
   is defined.
   Example:
     _GL_CXXALIAS_SYS (open, int, (const char *filename, int flags, ...));
 */
#if defined __cplusplus && defined GNULIB_NAMESPACE
  /* If we were to write
       rettype (*const func) parameters = ::func;
     like above in _GL_CXXALIAS_RPL_1, the compiler could optimize calls
     better (remove an indirection through a 'static' pointer variable),
     but then the _GL_CXXALIASWARN macro below would cause a warning not only
     for uses of ::func but also for uses of GNULIB_NAMESPACE::func.  */
# define _GL_CXXALIAS_SYS(func,rettype,parameters) \
    namespace GNULIB_NAMESPACE                     \
    {                                              \
      static rettype (*func) parameters = ::func;  \
    }                                              \
    _GL_EXTERN_C int _gl_cxxalias_dummy
#else
# define _GL_CXXALIAS_SYS(func,rettype,parameters) \
    _GL_EXTERN_C int _gl_cxxalias_dummy
#endif

/* _GL_CXXALIAS_SYS_CAST (func, rettype, parameters);
   is like  _GL_CXXALIAS_SYS (func, rettype, parameters);
   except that the C function func may have a slightly different declaration.
   A cast is used to silence the "invalid conversion" error that would
   otherwise occur.  */
#if defined __cplusplus && defined GNULIB_NAMESPACE
# define _GL_CXXALIAS_SYS_CAST(func,rettype,parameters) \
    namespace GNULIB_NAMESPACE                          \
    {                                                   \
      static rettype (*func) parameters =               \
        reinterpret_cast<rettype(*)parameters>(::func); \
    }                                                   \
    _GL_EXTERN_C int _gl_cxxalias_dummy
#else
# define _GL_CXXALIAS_SYS_CAST(func,rettype,parameters) \
    _GL_EXTERN_C int _gl_cxxalias_dummy
#endif

/* _GL_CXXALIAS_SYS_CAST2 (func, rettype, parameters, rettype2, parameters2);
   is like  _GL_CXXALIAS_SYS (func, rettype, parameters);
   except that the C function is picked among a set of overloaded functions,
   namely the one with rettype2 and parameters2.  Two consecutive casts
   are used to silence the "cannot find a match" and "invalid conversion"
   errors that would otherwise occur.  */
#if defined __cplusplus && defined GNULIB_NAMESPACE
  /* The outer cast must be a reinterpret_cast.
     The inner cast: When the function is defined as a set of overloaded
     functions, it works as a static_cast<>, choosing the designated variant.
     When the function is defined as a single variant, it works as a
     reinterpret_cast<>. The parenthesized cast syntax works both ways.  */
# define _GL_CXXALIAS_SYS_CAST2(func,rettype,parameters,rettype2,parameters2) \
    namespace GNULIB_NAMESPACE                                                \
    {                                                                         \
      static rettype (*func) parameters =                                     \
        reinterpret_cast<rettype(*)parameters>(                               \
          (rettype2(*)parameters2)(::func));                                  \
    }                                                                         \
    _GL_EXTERN_C int _gl_cxxalias_dummy
#else
# define _GL_CXXALIAS_SYS_CAST2(func,rettype,parameters,rettype2,parameters2) \
    _GL_EXTERN_C int _gl_cxxalias_dummy
#endif

/* _GL_CXXALIASWARN (func);
   causes a warning to be emitted when ::func is used but not when
   GNULIB_NAMESPACE::func is used.  func must be defined without overloaded
   variants.  */
#if defined __cplusplus && defined GNULIB_NAMESPACE
# define _GL_CXXALIASWARN(func) \
   _GL_CXXALIASWARN_1 (func, GNULIB_NAMESPACE)
# define _GL_CXXALIASWARN_1(func,namespace) \
   _GL_CXXALIASWARN_2 (func, namespace)
/* To work around GCC bug <http://gcc.gnu.org/bugzilla/show_bug.cgi?id=43881>,
   we enable the warning only when not optimizing.  */
# if !__OPTIMIZE__
#  define _GL_CXXALIASWARN_2(func,namespace) \
    _GL_WARN_ON_USE (func, \
                     "The symbol ::" #func " refers to the system function. " \
                     "Use " #namespace "::" #func " instead.")
# elif __GNUC__ >= 3 && GNULIB_STRICT_CHECKING
#  define _GL_CXXALIASWARN_2(func,namespace) \
     extern __typeof__ (func) func
# else
#  define _GL_CXXALIASWARN_2(func,namespace) \
     _GL_EXTERN_C int _gl_cxxalias_dummy
# endif
#else
# define _GL_CXXALIASWARN(func) \
    _GL_EXTERN_C int _gl_cxxalias_dummy
#endif

/* _GL_CXXALIASWARN1 (func, rettype, parameters_and_attributes);
   causes a warning to be emitted when the given overloaded variant of ::func
   is used but not when GNULIB_NAMESPACE::func is used.  */
#if defined __cplusplus && defined GNULIB_NAMESPACE
# define _GL_CXXALIASWARN1(func,rettype,parameters_and_attributes) \
   _GL_CXXALIASWARN1_1 (func, rettype, parameters_and_attributes, \
                        GNULIB_NAMESPACE)
# define _GL_CXXALIASWARN1_1(func,rettype,parameters_and_attributes,namespace) \
   _GL_CXXALIASWARN1_2 (func, rettype, parameters_and_attributes, namespace)
/* To work around GCC bug <http://gcc.gnu.org/bugzilla/show_bug.cgi?id=43881>,
   we enable the warning only when not optimizing.  */
# if !__OPTIMIZE__
#  define _GL_CXXALIASWARN1_2(func,rettype,parameters_and_attributes,namespace) \
    _GL_WARN_ON_USE_CXX (func, rettype, parameters_and_attributes, \
                         "The symbol ::" #func " refers to the system function. " \
                         "Use " #namespace "::" #func " instead.")
# elif __GNUC__ >= 3 && GNULIB_STRICT_CHECKING
#  define _GL_CXXALIASWARN1_2(func,rettype,parameters_and_attributes,namespace) \
     extern __typeof__ (func) func
# else
#  define _GL_CXXALIASWARN1_2(func,rettype,parameters_and_attributes,namespace) \
     _GL_EXTERN_C int _gl_cxxalias_dummy
# endif
#else
# define _GL_CXXALIASWARN1(func,rettype,parameters_and_attributes) \
    _GL_EXTERN_C int _gl_cxxalias_dummy
#endif

#endif /* _GL_CXXDEFS_H */