gnulib/import/extra/snippet/c++defs.h

   1 /* C++ compatible function declaration macros.
   2    Copyright (C) 2010-2016 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    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 /* Begin/end the GNULIB_NAMESPACE namespace.  */
  21 #if defined __cplusplus && defined GNULIB_NAMESPACE
  22 # define _GL_BEGIN_NAMESPACE namespace GNULIB_NAMESPACE {
  23 # define _GL_END_NAMESPACE }
  24 #else
  25 # define _GL_BEGIN_NAMESPACE
  26 # define _GL_END_NAMESPACE
  27 #endif
  28
  29 /* The three most frequent use cases of these macros are:
  30
  31    * For providing a substitute for a function that is missing on some
  32      platforms, but is declared and works fine on the platforms on which
  33      it exists:
  34
  35        #if @GNULIB_FOO@
  36        # if !@HAVE_FOO@
  37        _GL_FUNCDECL_SYS (foo, ...);
  38        # endif
  39        _GL_CXXALIAS_SYS (foo, ...);
  40        _GL_CXXALIASWARN (foo);
  41        #elif defined GNULIB_POSIXCHECK
  42        ...
  43        #endif
  44
  45    * For providing a replacement for a function that exists on all platforms,
  46      but is broken/insufficient and needs to be replaced on some platforms:
  47
  48        #if @GNULIB_FOO@
  49        # if @REPLACE_FOO@
  50        #  if !(defined __cplusplus && defined GNULIB_NAMESPACE)
  51        #   undef foo
  52        #   define foo rpl_foo
  53        #  endif
  54        _GL_FUNCDECL_RPL (foo, ...);
  55        _GL_CXXALIAS_RPL (foo, ...);
  56        # else
  57        _GL_CXXALIAS_SYS (foo, ...);
  58        # endif
  59        _GL_CXXALIASWARN (foo);
  60        #elif defined GNULIB_POSIXCHECK
  61        ...
  62        #endif
  63
  64    * For providing a replacement for a function that exists on some platforms
  65      but is broken/insufficient and needs to be replaced on some of them and
  66      is additionally either missing or undeclared on some other platforms:
  67
  68        #if @GNULIB_FOO@
  69        # if @REPLACE_FOO@
  70        #  if !(defined __cplusplus && defined GNULIB_NAMESPACE)
  71        #   undef foo
  72        #   define foo rpl_foo
  73        #  endif
  74        _GL_FUNCDECL_RPL (foo, ...);
  75        _GL_CXXALIAS_RPL (foo, ...);
  76        # else
  77        #  if !@HAVE_FOO@   or   if !@HAVE_DECL_FOO@
  78        _GL_FUNCDECL_SYS (foo, ...);
  79        #  endif
  80        _GL_CXXALIAS_SYS (foo, ...);
  81        # endif
  82        _GL_CXXALIASWARN (foo);
  83        #elif defined GNULIB_POSIXCHECK
  84        ...
  85        #endif
  86 */
  87
  88 /* _GL_EXTERN_C declaration;
  89    performs the declaration with C linkage.  */
  90 #if defined __cplusplus
  91 # define _GL_EXTERN_C extern "C"
  92 #else
  93 # define _GL_EXTERN_C extern
  94 #endif
  95
  96 /* _GL_FUNCDECL_RPL (func, rettype, parameters_and_attributes);
  97    declares a replacement function, named rpl_func, with the given prototype,
  98    consisting of return type, parameters, and attributes.
  99    Example:
 100      _GL_FUNCDECL_RPL (open, int, (const char *filename, int flags, ...)
 101                                   _GL_ARG_NONNULL ((1)));
 102  */
 103 #define _GL_FUNCDECL_RPL(func,rettype,parameters_and_attributes) \
 104   _GL_FUNCDECL_RPL_1 (rpl_##func, rettype, parameters_and_attributes)
 105 #define _GL_FUNCDECL_RPL_1(rpl_func,rettype,parameters_and_attributes) \
 106   _GL_EXTERN_C rettype rpl_func parameters_and_attributes
 107
 108 /* _GL_FUNCDECL_SYS (func, rettype, parameters_and_attributes);
 109    declares the system function, named func, with the given prototype,
 110    consisting of return type, parameters, and attributes.
 111    Example:
 112      _GL_FUNCDECL_SYS (open, int, (const char *filename, int flags, ...)
 113                                   _GL_ARG_NONNULL ((1)));
 114  */
 115 #define _GL_FUNCDECL_SYS(func,rettype,parameters_and_attributes) \
 116   _GL_EXTERN_C rettype func parameters_and_attributes
 117
 118 /* _GL_CXXALIAS_RPL (func, rettype, parameters);
 119    declares a C++ alias called GNULIB_NAMESPACE::func
 120    that redirects to rpl_func, if GNULIB_NAMESPACE is defined.
 121    Example:
 122      _GL_CXXALIAS_RPL (open, int, (const char *filename, int flags, ...));
 123
 124    Wrapping rpl_func in an object with an inline conversion operator
 125    avoids a reference to rpl_func unless GNULIB_NAMESPACE::func is
 126    actually used in the program.  */
 127 #define _GL_CXXALIAS_RPL(func,rettype,parameters) \
 128   _GL_CXXALIAS_RPL_1 (func, rpl_##func, rettype, parameters)
 129 #if defined __cplusplus && defined GNULIB_NAMESPACE
 130 # define _GL_CXXALIAS_RPL_1(func,rpl_func,rettype,parameters) \
 131     namespace GNULIB_NAMESPACE                                \
 132     {                                                         \
 133       static const struct _gl_ ## func ## _wrapper            \
 134       {                                                       \
 135         typedef rettype (*type) parameters;                   \
 136         inline type rpl () const { return ::rpl_func; }       \
 137         inline operator type () const  { return rpl (); }     \
 138       } func = {};                                            \
 139     }                                                         \
 140     _GL_EXTERN_C int _gl_cxxalias_dummy
 141 #else
 142 # define _GL_CXXALIAS_RPL_1(func,rpl_func,rettype,parameters) \
 143     _GL_EXTERN_C int _gl_cxxalias_dummy
 144 #endif
 145
 146 /* _GL_CXXALIAS_RPL_CAST_1 (func, rpl_func, rettype, parameters);
 147    is like  _GL_CXXALIAS_RPL_1 (func, rpl_func, rettype, parameters);
 148    except that the C function rpl_func may have a slightly different
 149    declaration.  A cast is used to silence the "invalid conversion" error
 150    that would otherwise occur.  */
 151 #if defined __cplusplus && defined GNULIB_NAMESPACE
 152 # define _GL_CXXALIAS_RPL_CAST_1(func,rpl_func,rettype,parameters) \
 153     namespace GNULIB_NAMESPACE                                     \
 154     {                                                              \
 155       static const struct _gl_ ## func ## _wrapper                 \
 156       {                                                            \
 157         typedef rettype (*type) parameters;                        \
 158         inline type rpl () const                                   \
 159         { return reinterpret_cast<type>(::rpl_func); }             \
 160         inline operator type () const { return rpl (); }           \
 161       } func = {};                                                 \
 162     }                                                              \
 163     _GL_EXTERN_C int _gl_cxxalias_dummy
 164 #else
 165 # define _GL_CXXALIAS_RPL_CAST_1(func,rpl_func,rettype,parameters) \
 166     _GL_EXTERN_C int _gl_cxxalias_dummy
 167 #endif
 168
 169 /* _GL_CXXALIAS_SYS (func, rettype, parameters);
 170    declares a C++ alias called GNULIB_NAMESPACE::func
 171    that redirects to the system provided function func, if GNULIB_NAMESPACE
 172    is defined.
 173    Example:
 174      _GL_CXXALIAS_SYS (open, int, (const char *filename, int flags, ...));
 175
 176    Wrapping func in an object with an inline conversion operator
 177    avoids a reference to func unless GNULIB_NAMESPACE::func is
 178    actually used in the program.  */
 179 #if defined __cplusplus && defined GNULIB_NAMESPACE
 180 # define _GL_CXXALIAS_SYS(func,rettype,parameters)            \
 181     namespace GNULIB_NAMESPACE                                \
 182     {                                                         \
 183       static const struct _gl_ ## func ## _wrapper            \
 184       {                                                       \
 185         typedef rettype (*type) parameters;                   \
 186         inline type rpl () const { return ::func; }           \
 187         inline operator type () const { return rpl (); }      \
 188       } func = {};                                            \
 189     }                                              \
 190     _GL_EXTERN_C int _gl_cxxalias_dummy
 191 #else
 192 # define _GL_CXXALIAS_SYS(func,rettype,parameters) \
 193     _GL_EXTERN_C int _gl_cxxalias_dummy
 194 #endif
 195
 196 /* _GL_CXXALIAS_SYS_CAST (func, rettype, parameters);
 197    is like  _GL_CXXALIAS_SYS (func, rettype, parameters);
 198    except that the C function func may have a slightly different declaration.
 199    A cast is used to silence the "invalid conversion" error that would
 200    otherwise occur.  */
 201 #if defined __cplusplus && defined GNULIB_NAMESPACE
 202 # define _GL_CXXALIAS_SYS_CAST(func,rettype,parameters) \
 203     namespace GNULIB_NAMESPACE                          \
 204     {                                                   \
 205       static const struct _gl_ ## func ## _wrapper      \
 206       {                                                 \
 207         typedef rettype (*type) parameters;             \
 208         inline type rpl () const                        \
 209         { return reinterpret_cast<type>(::func); }      \
 210         inline operator type () const { return rpl (); }\
 211       } func = {};                                      \
 212     }                                                   \
 213     _GL_EXTERN_C int _gl_cxxalias_dummy
 214 #else
 215 # define _GL_CXXALIAS_SYS_CAST(func,rettype,parameters) \
 216     _GL_EXTERN_C int _gl_cxxalias_dummy
 217 #endif
 218
 219 /* _GL_CXXALIAS_SYS_CAST2 (func, rettype, parameters, rettype2, parameters2);
 220    is like  _GL_CXXALIAS_SYS (func, rettype, parameters);
 221    except that the C function is picked among a set of overloaded functions,
 222    namely the one with rettype2 and parameters2.  Two consecutive casts
 223    are used to silence the "cannot find a match" and "invalid conversion"
 224    errors that would otherwise occur.  */
 225 #if defined __cplusplus && defined GNULIB_NAMESPACE
 226   /* The outer cast must be a reinterpret_cast.
 227      The inner cast: When the function is defined as a set of overloaded
 228      functions, it works as a static_cast<>, choosing the designated variant.
 229      When the function is defined as a single variant, it works as a
 230      reinterpret_cast<>. The parenthesized cast syntax works both ways.  */
 231 # define _GL_CXXALIAS_SYS_CAST2(func,rettype,parameters,rettype2,parameters2) \
 232     namespace GNULIB_NAMESPACE                                                \
 233     {                                                                         \
 234       static const struct _gl_ ## func ## _wrapper                            \
 235       {                                                                       \
 236         typedef rettype (*type) parameters;                                   \
 237                                                                               \
 238         inline type rpl () const                                              \
 239         { return reinterpret_cast<type>((rettype2 (*) parameters2)(::func)); }\
 240                                                                               \
 241         inline operator type () const { return rpl (); }                      \
 242       } func = {};                                                            \
 243     }                                                                         \
 244     _GL_EXTERN_C int _gl_cxxalias_dummy
 245 #else
 246 # define _GL_CXXALIAS_SYS_CAST2(func,rettype,parameters,rettype2,parameters2) \
 247     _GL_EXTERN_C int _gl_cxxalias_dummy
 248 #endif
 249
 250 /* _GL_CXXALIASWARN (func);
 251    causes a warning to be emitted when ::func is used but not when
 252    GNULIB_NAMESPACE::func is used.  func must be defined without overloaded
 253    variants.  */
 254 #if defined __cplusplus && defined GNULIB_NAMESPACE
 255 # define _GL_CXXALIASWARN(func) \
 256    _GL_CXXALIASWARN_1 (func, GNULIB_NAMESPACE)
 257 # define _GL_CXXALIASWARN_1(func,namespace) \
 258    _GL_CXXALIASWARN_2 (func, namespace)
 259 /* To work around GCC bug <http://gcc.gnu.org/bugzilla/show_bug.cgi?id=43881>,
 260    we enable the warning only when not optimizing.  */
 261 # if !__OPTIMIZE__
 262 #  define _GL_CXXALIASWARN_2(func,namespace) \
 263     _GL_WARN_ON_USE (func, \
 264                      "The symbol ::" #func " refers to the system function. " \
 265                      "Use " #namespace "::" #func " instead.")
 266 # elif __GNUC__ >= 3 && GNULIB_STRICT_CHECKING
 267 #  define _GL_CXXALIASWARN_2(func,namespace) \
 268      extern __typeof__ (func) func
 269 # else
 270 #  define _GL_CXXALIASWARN_2(func,namespace) \
 271      _GL_EXTERN_C int _gl_cxxalias_dummy
 272 # endif
 273 #else
 274 # define _GL_CXXALIASWARN(func) \
 275     _GL_EXTERN_C int _gl_cxxalias_dummy
 276 #endif
 277
 278 /* _GL_CXXALIASWARN1 (func, rettype, parameters_and_attributes);
 279    causes a warning to be emitted when the given overloaded variant of ::func
 280    is used but not when GNULIB_NAMESPACE::func is used.  */
 281 #if defined __cplusplus && defined GNULIB_NAMESPACE
 282 # define _GL_CXXALIASWARN1(func,rettype,parameters_and_attributes) \
 283    _GL_CXXALIASWARN1_1 (func, rettype, parameters_and_attributes, \
 284                         GNULIB_NAMESPACE)
 285 # define _GL_CXXALIASWARN1_1(func,rettype,parameters_and_attributes,namespace) \
 286    _GL_CXXALIASWARN1_2 (func, rettype, parameters_and_attributes, namespace)
 287 /* To work around GCC bug <http://gcc.gnu.org/bugzilla/show_bug.cgi?id=43881>,
 288    we enable the warning only when not optimizing.  */
 289 # if !__OPTIMIZE__
 290 #  define _GL_CXXALIASWARN1_2(func,rettype,parameters_and_attributes,namespace) \
 291     _GL_WARN_ON_USE_CXX (func, rettype, parameters_and_attributes, \
 292                          "The symbol ::" #func " refers to the system function. " \
 293                          "Use " #namespace "::" #func " instead.")
 294 # elif __GNUC__ >= 3 && GNULIB_STRICT_CHECKING
 295 #  define _GL_CXXALIASWARN1_2(func,rettype,parameters_and_attributes,namespace) \
 296      extern __typeof__ (func) func
 297 # else
 298 #  define _GL_CXXALIASWARN1_2(func,rettype,parameters_and_attributes,namespace) \
 299      _GL_EXTERN_C int _gl_cxxalias_dummy
 300 # endif
 301 #else
 302 # define _GL_CXXALIASWARN1(func,rettype,parameters_and_attributes) \
 303     _GL_EXTERN_C int _gl_cxxalias_dummy
 304 #endif
 305
 306 #endif /* _GL_CXXDEFS_H */