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cPPdefs.h
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1 /* C++ compatible function declaration macros.
2  Copyright (C) 2010-2011 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 /* 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_RPL_CAST_1 (func, rpl_func, rettype, parameters);
130  is like _GL_CXXALIAS_RPL_1 (func, rpl_func, rettype, parameters);
131  except that the C function rpl_func may have a slightly different
132  declaration. A cast is used to silence the "invalid conversion" error
133  that would otherwise occur. */
134 #if defined __cplusplus && defined GNULIB_NAMESPACE
135 # define _GL_CXXALIAS_RPL_CAST_1(func,rpl_func,rettype,parameters) \
136  namespace GNULIB_NAMESPACE \
137  { \
138  rettype (*const func) parameters = \
139  reinterpret_cast<rettype(*)parameters>(::rpl_func); \
140  } \
141  _GL_EXTERN_C int _gl_cxxalias_dummy
142 #else
143 # define _GL_CXXALIAS_RPL_CAST_1(func,rpl_func,rettype,parameters) \
144  _GL_EXTERN_C int _gl_cxxalias_dummy
145 #endif
146 
147 /* _GL_CXXALIAS_SYS (func, rettype, parameters);
148  declares a C++ alias called GNULIB_NAMESPACE::func
149  that redirects to the system provided function func, if GNULIB_NAMESPACE
150  is defined.
151  Example:
152  _GL_CXXALIAS_SYS (open, int, (const char *filename, int flags, ...));
153  */
154 #if defined __cplusplus && defined GNULIB_NAMESPACE
155  /* If we were to write
156  rettype (*const func) parameters = ::func;
157  like above in _GL_CXXALIAS_RPL_1, the compiler could optimize calls
158  better (remove an indirection through a 'static' pointer variable),
159  but then the _GL_CXXALIASWARN macro below would cause a warning not only
160  for uses of ::func but also for uses of GNULIB_NAMESPACE::func. */
161 # define _GL_CXXALIAS_SYS(func,rettype,parameters) \
162  namespace GNULIB_NAMESPACE \
163  { \
164  static rettype (*func) parameters = ::func; \
165  } \
166  _GL_EXTERN_C int _gl_cxxalias_dummy
167 #else
168 # define _GL_CXXALIAS_SYS(func,rettype,parameters) \
169  _GL_EXTERN_C int _gl_cxxalias_dummy
170 #endif
171 
172 /* _GL_CXXALIAS_SYS_CAST (func, rettype, parameters);
173  is like _GL_CXXALIAS_SYS (func, rettype, parameters);
174  except that the C function func may have a slightly different declaration.
175  A cast is used to silence the "invalid conversion" error that would
176  otherwise occur. */
177 #if defined __cplusplus && defined GNULIB_NAMESPACE
178 # define _GL_CXXALIAS_SYS_CAST(func,rettype,parameters) \
179  namespace GNULIB_NAMESPACE \
180  { \
181  static rettype (*func) parameters = \
182  reinterpret_cast<rettype(*)parameters>(::func); \
183  } \
184  _GL_EXTERN_C int _gl_cxxalias_dummy
185 #else
186 # define _GL_CXXALIAS_SYS_CAST(func,rettype,parameters) \
187  _GL_EXTERN_C int _gl_cxxalias_dummy
188 #endif
189 
190 /* _GL_CXXALIAS_SYS_CAST2 (func, rettype, parameters, rettype2, parameters2);
191  is like _GL_CXXALIAS_SYS (func, rettype, parameters);
192  except that the C function is picked among a set of overloaded functions,
193  namely the one with rettype2 and parameters2. Two consecutive casts
194  are used to silence the "cannot find a match" and "invalid conversion"
195  errors that would otherwise occur. */
196 #if defined __cplusplus && defined GNULIB_NAMESPACE
197  /* The outer cast must be a reinterpret_cast.
198  The inner cast: When the function is defined as a set of overloaded
199  functions, it works as a static_cast<>, choosing the designated variant.
200  When the function is defined as a single variant, it works as a
201  reinterpret_cast<>. The parenthesized cast syntax works both ways. */
202 # define _GL_CXXALIAS_SYS_CAST2(func,rettype,parameters,rettype2,parameters2) \
203  namespace GNULIB_NAMESPACE \
204  { \
205  static rettype (*func) parameters = \
206  reinterpret_cast<rettype(*)parameters>( \
207  (rettype2(*)parameters2)(::func)); \
208  } \
209  _GL_EXTERN_C int _gl_cxxalias_dummy
210 #else
211 # define _GL_CXXALIAS_SYS_CAST2(func,rettype,parameters,rettype2,parameters2) \
212  _GL_EXTERN_C int _gl_cxxalias_dummy
213 #endif
214 
215 /* _GL_CXXALIASWARN (func);
216  causes a warning to be emitted when ::func is used but not when
217  GNULIB_NAMESPACE::func is used. func must be defined without overloaded
218  variants. */
219 #if defined __cplusplus && defined GNULIB_NAMESPACE
220 # define _GL_CXXALIASWARN(func) \
221  _GL_CXXALIASWARN_1 (func, GNULIB_NAMESPACE)
222 # define _GL_CXXALIASWARN_1(func,namespace) \
223  _GL_CXXALIASWARN_2 (func, namespace)
224 /* To work around GCC bug <http://gcc.gnu.org/bugzilla/show_bug.cgi?id=43881>,
225  we enable the warning only when not optimizing. */
226 # if !__OPTIMIZE__
227 # define _GL_CXXALIASWARN_2(func,namespace) \
228  _GL_WARN_ON_USE (func, \
229  "The symbol ::" #func " refers to the system function. " \
230  "Use " #namespace "::" #func " instead.")
231 # elif __GNUC__ >= 3 && GNULIB_STRICT_CHECKING
232 # define _GL_CXXALIASWARN_2(func,namespace) \
233  extern __typeof__ (func) func
234 # else
235 # define _GL_CXXALIASWARN_2(func,namespace) \
236  _GL_EXTERN_C int _gl_cxxalias_dummy
237 # endif
238 #else
239 # define _GL_CXXALIASWARN(func) \
240  _GL_EXTERN_C int _gl_cxxalias_dummy
241 #endif
242 
243 /* _GL_CXXALIASWARN1 (func, rettype, parameters_and_attributes);
244  causes a warning to be emitted when the given overloaded variant of ::func
245  is used but not when GNULIB_NAMESPACE::func is used. */
246 #if defined __cplusplus && defined GNULIB_NAMESPACE
247 # define _GL_CXXALIASWARN1(func,rettype,parameters_and_attributes) \
248  _GL_CXXALIASWARN1_1 (func, rettype, parameters_and_attributes, \
249  GNULIB_NAMESPACE)
250 # define _GL_CXXALIASWARN1_1(func,rettype,parameters_and_attributes,namespace) \
251  _GL_CXXALIASWARN1_2 (func, rettype, parameters_and_attributes, namespace)
252 /* To work around GCC bug <http://gcc.gnu.org/bugzilla/show_bug.cgi?id=43881>,
253  we enable the warning only when not optimizing. */
254 # if !__OPTIMIZE__
255 # define _GL_CXXALIASWARN1_2(func,rettype,parameters_and_attributes,namespace) \
256  _GL_WARN_ON_USE_CXX (func, rettype, parameters_and_attributes, \
257  "The symbol ::" #func " refers to the system function. " \
258  "Use " #namespace "::" #func " instead.")
259 # elif __GNUC__ >= 3 && GNULIB_STRICT_CHECKING
260 # define _GL_CXXALIASWARN1_2(func,rettype,parameters_and_attributes,namespace) \
261  extern __typeof__ (func) func
262 # else
263 # define _GL_CXXALIASWARN1_2(func,rettype,parameters_and_attributes,namespace) \
264  _GL_EXTERN_C int _gl_cxxalias_dummy
265 # endif
266 #else
267 # define _GL_CXXALIASWARN1(func,rettype,parameters_and_attributes) \
268  _GL_EXTERN_C int _gl_cxxalias_dummy
269 #endif
270 
271 #endif /* _GL_CXXDEFS_H */