lib/build-aux/c++defs.h

   1 /* C++ compatible function declaration macros.
   2    Copyright (C) 2010 Free Software Foundation, Inc.
   3
   4    This program is free software: you can redistribute it and/or modify it
   5    under the terms of the GNU General Public License as published
   6    by the Free Software Foundation; either version 3 of the License, or
   7    (at your option) any later version.
   8
   9    This program is distributed in the hope that it will be useful,
  10    but WITHOUT ANY WARRANTY; without even the implied warranty of
  11    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  12    Lesser General Public License for more details.
  13
  14    You should have received a copy of the GNU General Public License
  15    along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
  16
  17 #ifndef _GL_CXXDEFS_H
  18 #define _GL_CXXDEFS_H
  19
  20 /* The three most frequent use cases of these macros are:
  21
  22    * For providing a substitute for a function that is missing on some
  23      platforms, but is declared and works fine on the platforms on which
  24      it exists:
  25
  26        #if @GNULIB_FOO@
  27        # if !@HAVE_FOO@
  28        _GL_FUNCDECL_SYS (foo, ...);
  29        # endif
  30        _GL_CXXALIAS_SYS (foo, ...);
  31        _GL_CXXALIASWARN (foo);
  32        #elif defined GNULIB_POSIXCHECK
  33        ...
  34        #endif
  35
  36    * For providing a replacement for a function that exists on all platforms,
  37      but is broken/insufficient and needs to be replaced on some platforms:
  38
  39        #if @GNULIB_FOO@
  40        # if @REPLACE_FOO@
  41        #  if !(defined __cplusplus && defined GNULIB_NAMESPACE)
  42        #   undef foo
  43        #   define foo rpl_foo
  44        #  endif
  45        _GL_FUNCDECL_RPL (foo, ...);
  46        _GL_CXXALIAS_RPL (foo, ...);
  47        # else
  48        _GL_CXXALIAS_SYS (foo, ...);
  49        # endif
  50        _GL_CXXALIASWARN (foo);
  51        #elif defined GNULIB_POSIXCHECK
  52        ...
  53        #endif
  54
  55    * For providing a replacement for a function that exists on some platforms
  56      but is broken/insufficient and needs to be replaced on some of them and
  57      is additionally either missing or undeclared on some other platforms:
  58
  59        #if @GNULIB_FOO@
  60        # if @REPLACE_FOO@
  61        #  if !(defined __cplusplus && defined GNULIB_NAMESPACE)
  62        #   undef foo
  63        #   define foo rpl_foo
  64        #  endif
  65        _GL_FUNCDECL_RPL (foo, ...);
  66        _GL_CXXALIAS_RPL (foo, ...);
  67        # else
  68        #  if !@HAVE_FOO@   or   if !@HAVE_DECL_FOO@
  69        _GL_FUNCDECL_SYS (foo, ...);
  70        #  endif
  71        _GL_CXXALIAS_SYS (foo, ...);
  72        # endif
  73        _GL_CXXALIASWARN (foo);
  74        #elif defined GNULIB_POSIXCHECK
  75        ...
  76        #endif
  77 */
  78
  79 /* _GL_EXTERN_C declaration;
  80    performs the declaration with C linkage.  */
  81 #if defined __cplusplus
  82 # define _GL_EXTERN_C extern "C"
  83 #else
  84 # define _GL_EXTERN_C extern
  85 #endif
  86
  87 /* _GL_FUNCDECL_RPL (func, rettype, parameters_and_attributes);
  88    declares a replacement function, named rpl_func, with the given prototype,
  89    consisting of return type, parameters, and attributes.
  90    Example:
  91      _GL_FUNCDECL_RPL (open, int, (const char *filename, int flags, ...)
  92                                   _GL_ARG_NONNULL ((1)));
  93  */
  94 #define _GL_FUNCDECL_RPL(func,rettype,parameters_and_attributes) \
  95   _GL_FUNCDECL_RPL_1 (rpl_##func, rettype, parameters_and_attributes)
  96 #define _GL_FUNCDECL_RPL_1(rpl_func,rettype,parameters_and_attributes) \
  97   _GL_EXTERN_C rettype rpl_func parameters_and_attributes
  98
  99 /* _GL_FUNCDECL_SYS (func, rettype, parameters_and_attributes);
 100    declares the system function, named func, with the given prototype,
 101    consisting of return type, parameters, and attributes.
 102    Example:
 103      _GL_FUNCDECL_SYS (open, int, (const char *filename, int flags, ...)
 104                                   _GL_ARG_NONNULL ((1)));
 105  */
 106 #define _GL_FUNCDECL_SYS(func,rettype,parameters_and_attributes) \
 107   _GL_EXTERN_C rettype func parameters_and_attributes
 108
 109 /* _GL_CXXALIAS_RPL (func, rettype, parameters);
 110    declares a C++ alias called GNULIB_NAMESPACE::func
 111    that redirects to rpl_func, if GNULIB_NAMESPACE is defined.
 112    Example:
 113      _GL_CXXALIAS_RPL (open, int, (const char *filename, int flags, ...));
 114  */
 115 #define _GL_CXXALIAS_RPL(func,rettype,parameters) \
 116   _GL_CXXALIAS_RPL_1 (func, rpl_##func, rettype, parameters)
 117 #if defined __cplusplus && defined GNULIB_NAMESPACE
 118 # define _GL_CXXALIAS_RPL_1(func,rpl_func,rettype,parameters) \
 119     namespace GNULIB_NAMESPACE                                \
 120     {                                                         \
 121       rettype (*const func) parameters = ::rpl_func;          \
 122     }                                                         \
 123     _GL_EXTERN_C int _gl_cxxalias_dummy
 124 #else
 125 # define _GL_CXXALIAS_RPL_1(func,rpl_func,rettype,parameters) \
 126     _GL_EXTERN_C int _gl_cxxalias_dummy
 127 #endif
 128
 129 /* _GL_CXXALIAS_SYS (func, rettype, parameters);
 130    declares a C++ alias called GNULIB_NAMESPACE::func
 131    that redirects to the system provided function func, if GNULIB_NAMESPACE
 132    is defined.
 133    Example:
 134      _GL_CXXALIAS_SYS (open, int, (const char *filename, int flags, ...));
 135  */
 136 #if defined __cplusplus && defined GNULIB_NAMESPACE
 137   /* If we were to write
 138        rettype (*const func) parameters = ::func;
 139      like above in _GL_CXXALIAS_RPL_1, the compiler could optimize calls
 140      better (remove an indirection through a 'static' pointer variable),
 141      but then the _GL_CXXALIASWARN macro below would cause a warning not only
 142      for uses of ::func but also for uses of GNULIB_NAMESPACE::func.  */
 143 # define _GL_CXXALIAS_SYS(func,rettype,parameters) \
 144     namespace GNULIB_NAMESPACE                     \
 145     {                                              \
 146       static rettype (*func) parameters = ::func;  \
 147     }                                              \
 148     _GL_EXTERN_C int _gl_cxxalias_dummy
 149 #else
 150 # define _GL_CXXALIAS_SYS(func,rettype,parameters) \
 151     _GL_EXTERN_C int _gl_cxxalias_dummy
 152 #endif
 153
 154 /* _GL_CXXALIAS_SYS_CAST (func, rettype, parameters);
 155    is like  _GL_CXXALIAS_SYS (func, rettype, parameters);
 156    except that the C function func may have a slightly different declaration.
 157    A cast is used to silence the "invalid conversion" error that would
 158    otherwise occur.  */
 159 #if defined __cplusplus && defined GNULIB_NAMESPACE
 160 # define _GL_CXXALIAS_SYS_CAST(func,rettype,parameters) \
 161     namespace GNULIB_NAMESPACE                          \
 162     {                                                   \
 163       static rettype (*func) parameters =               \
 164         reinterpret_cast<rettype(*)parameters>(::func); \
 165     }                                                   \
 166     _GL_EXTERN_C int _gl_cxxalias_dummy
 167 #else
 168 # define _GL_CXXALIAS_SYS_CAST(func,rettype,parameters) \
 169     _GL_EXTERN_C int _gl_cxxalias_dummy
 170 #endif
 171
 172 /* _GL_CXXALIAS_SYS_CAST2 (func, rettype, parameters, rettype2, parameters2);
 173    is like  _GL_CXXALIAS_SYS (func, rettype, parameters);
 174    except that the C function is picked among a set of overloaded functions,
 175    namely the one with rettype2 and parameters2.  Two consecutive casts
 176    are used to silence the "cannot find a match" and "invalid conversion"
 177    errors that would otherwise occur.  */
 178 #if defined __cplusplus && defined GNULIB_NAMESPACE
 179   /* The outer cast must be a reinterpret_cast.
 180      The inner cast: When the function is defined as a set of overloaded
 181      functions, it works as a static_cast<>, choosing the designated variant.
 182      When the function is defined as a single variant, it works as a
 183      reinterpret_cast<>. The parenthesized cast syntax works both ways.  */
 184 # define _GL_CXXALIAS_SYS_CAST2(func,rettype,parameters,rettype2,parameters2) \
 185     namespace GNULIB_NAMESPACE                                                \
 186     {                                                                         \
 187       static rettype (*func) parameters =                                     \
 188         reinterpret_cast<rettype(*)parameters>(                               \
 189           (rettype2(*)parameters2)(::func));                                  \
 190     }                                                                         \
 191     _GL_EXTERN_C int _gl_cxxalias_dummy
 192 #else
 193 # define _GL_CXXALIAS_SYS_CAST2(func,rettype,parameters,rettype2,parameters2) \
 194     _GL_EXTERN_C int _gl_cxxalias_dummy
 195 #endif
 196
 197 /* _GL_CXXALIASWARN (func);
 198    causes a warning to be emitted when ::func is used but not when
 199    GNULIB_NAMESPACE::func is used.  func must be defined without overloaded
 200    variants.  */
 201 #if defined __cplusplus && defined GNULIB_NAMESPACE
 202 # define _GL_CXXALIASWARN(func) \
 203    _GL_CXXALIASWARN_1 (func, GNULIB_NAMESPACE)
 204 # define _GL_CXXALIASWARN_1(func,namespace) \
 205    _GL_CXXALIASWARN_2 (func, namespace)
 206 # define _GL_CXXALIASWARN_2(func,namespace) \
 207    _GL_WARN_ON_USE (func, \
 208                     "The symbol ::" #func " refers to the system function. " \
 209                     "Use " #namespace "::" #func " instead.")
 210 #else
 211 # define _GL_CXXALIASWARN(func) \
 212     _GL_EXTERN_C int _gl_cxxalias_dummy
 213 #endif
 214
 215 /* _GL_CXXALIASWARN1 (func, rettype, parameters_and_attributes);
 216    causes a warning to be emitted when the given overloaded variant of ::func
 217    is used but not when GNULIB_NAMESPACE::func is used.  */
 218 #if defined __cplusplus && defined GNULIB_NAMESPACE
 219 # define _GL_CXXALIASWARN1(func,rettype,parameters_and_attributes) \
 220    _GL_CXXALIASWARN1_1 (func, rettype, parameters_and_attributes, \
 221                         GNULIB_NAMESPACE)
 222 # define _GL_CXXALIASWARN1_1(func,rettype,parameters_and_attributes,namespace) \
 223    _GL_CXXALIASWARN1_2 (func, rettype, parameters_and_attributes, namespace)
 224 # define _GL_CXXALIASWARN1_2(func,rettype,parameters_and_attributes,namespace) \
 225    _GL_WARN_ON_USE_CXX (func, rettype, parameters_and_attributes, \
 226                         "The symbol ::" #func " refers to the system function. " \
 227                         "Use " #namespace "::" #func " instead.")
 228 #else
 229 # define _GL_CXXALIASWARN1(func,rettype,parameters_and_attributes) \
 230     _GL_EXTERN_C int _gl_cxxalias_dummy
 231 #endif
 232
 233 #endif /* _GL_CXXDEFS_H */