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-rw-r--r--gl/c++defs.h331
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1/* C++ compatible function declaration macros.
2 Copyright (C) 2010-2023 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 Lesser General Public License as published
6 by the Free Software Foundation; either version 2 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 Lesser General Public License
15 along with this program. If not, see <https://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 \
137 inline operator type () const \
138 { \
139 return ::rpl_func; \
140 } \
141 } func = {}; \
142 } \
143 _GL_EXTERN_C int _gl_cxxalias_dummy
144#else
145# define _GL_CXXALIAS_RPL_1(func,rpl_func,rettype,parameters) \
146 _GL_EXTERN_C int _gl_cxxalias_dummy
147#endif
148
149/* _GL_CXXALIAS_MDA (func, rettype, parameters);
150 is to be used when func is a Microsoft deprecated alias, on native Windows.
151 It declares a C++ alias called GNULIB_NAMESPACE::func
152 that redirects to _func, if GNULIB_NAMESPACE is defined.
153 Example:
154 _GL_CXXALIAS_MDA (open, int, (const char *filename, int flags, ...));
155 */
156#define _GL_CXXALIAS_MDA(func,rettype,parameters) \
157 _GL_CXXALIAS_RPL_1 (func, _##func, rettype, parameters)
158
159/* _GL_CXXALIAS_RPL_CAST_1 (func, rpl_func, rettype, parameters);
160 is like _GL_CXXALIAS_RPL_1 (func, rpl_func, rettype, parameters);
161 except that the C function rpl_func may have a slightly different
162 declaration. A cast is used to silence the "invalid conversion" error
163 that would otherwise occur. */
164#if defined __cplusplus && defined GNULIB_NAMESPACE
165# define _GL_CXXALIAS_RPL_CAST_1(func,rpl_func,rettype,parameters) \
166 namespace GNULIB_NAMESPACE \
167 { \
168 static const struct _gl_ ## func ## _wrapper \
169 { \
170 typedef rettype (*type) parameters; \
171 \
172 inline operator type () const \
173 { \
174 return reinterpret_cast<type>(::rpl_func); \
175 } \
176 } func = {}; \
177 } \
178 _GL_EXTERN_C int _gl_cxxalias_dummy
179#else
180# define _GL_CXXALIAS_RPL_CAST_1(func,rpl_func,rettype,parameters) \
181 _GL_EXTERN_C int _gl_cxxalias_dummy
182#endif
183
184/* _GL_CXXALIAS_MDA_CAST (func, rettype, parameters);
185 is like _GL_CXXALIAS_MDA (func, rettype, parameters);
186 except that the C function func may have a slightly different declaration.
187 A cast is used to silence the "invalid conversion" error that would
188 otherwise occur. */
189#define _GL_CXXALIAS_MDA_CAST(func,rettype,parameters) \
190 _GL_CXXALIAS_RPL_CAST_1 (func, _##func, rettype, parameters)
191
192/* _GL_CXXALIAS_SYS (func, rettype, parameters);
193 declares a C++ alias called GNULIB_NAMESPACE::func
194 that redirects to the system provided function func, if GNULIB_NAMESPACE
195 is defined.
196 Example:
197 _GL_CXXALIAS_SYS (open, int, (const char *filename, int flags, ...));
198
199 Wrapping func in an object with an inline conversion operator
200 avoids a reference to func unless GNULIB_NAMESPACE::func is
201 actually used in the program. */
202#if defined __cplusplus && defined GNULIB_NAMESPACE
203# define _GL_CXXALIAS_SYS(func,rettype,parameters) \
204 namespace GNULIB_NAMESPACE \
205 { \
206 static const struct _gl_ ## func ## _wrapper \
207 { \
208 typedef rettype (*type) parameters; \
209 \
210 inline operator type () const \
211 { \
212 return ::func; \
213 } \
214 } func = {}; \
215 } \
216 _GL_EXTERN_C int _gl_cxxalias_dummy
217#else
218# define _GL_CXXALIAS_SYS(func,rettype,parameters) \
219 _GL_EXTERN_C int _gl_cxxalias_dummy
220#endif
221
222/* _GL_CXXALIAS_SYS_CAST (func, rettype, parameters);
223 is like _GL_CXXALIAS_SYS (func, rettype, parameters);
224 except that the C function func may have a slightly different declaration.
225 A cast is used to silence the "invalid conversion" error that would
226 otherwise occur. */
227#if defined __cplusplus && defined GNULIB_NAMESPACE
228# define _GL_CXXALIAS_SYS_CAST(func,rettype,parameters) \
229 namespace GNULIB_NAMESPACE \
230 { \
231 static const struct _gl_ ## func ## _wrapper \
232 { \
233 typedef rettype (*type) parameters; \
234 \
235 inline operator type () const \
236 { \
237 return reinterpret_cast<type>(::func); \
238 } \
239 } func = {}; \
240 } \
241 _GL_EXTERN_C int _gl_cxxalias_dummy
242#else
243# define _GL_CXXALIAS_SYS_CAST(func,rettype,parameters) \
244 _GL_EXTERN_C int _gl_cxxalias_dummy
245#endif
246
247/* _GL_CXXALIAS_SYS_CAST2 (func, rettype, parameters, rettype2, parameters2);
248 is like _GL_CXXALIAS_SYS (func, rettype, parameters);
249 except that the C function is picked among a set of overloaded functions,
250 namely the one with rettype2 and parameters2. Two consecutive casts
251 are used to silence the "cannot find a match" and "invalid conversion"
252 errors that would otherwise occur. */
253#if defined __cplusplus && defined GNULIB_NAMESPACE
254 /* The outer cast must be a reinterpret_cast.
255 The inner cast: When the function is defined as a set of overloaded
256 functions, it works as a static_cast<>, choosing the designated variant.
257 When the function is defined as a single variant, it works as a
258 reinterpret_cast<>. The parenthesized cast syntax works both ways. */
259# define _GL_CXXALIAS_SYS_CAST2(func,rettype,parameters,rettype2,parameters2) \
260 namespace GNULIB_NAMESPACE \
261 { \
262 static const struct _gl_ ## func ## _wrapper \
263 { \
264 typedef rettype (*type) parameters; \
265 \
266 inline operator type () const \
267 { \
268 return reinterpret_cast<type>((rettype2 (*) parameters2)(::func)); \
269 } \
270 } func = {}; \
271 } \
272 _GL_EXTERN_C int _gl_cxxalias_dummy
273#else
274# define _GL_CXXALIAS_SYS_CAST2(func,rettype,parameters,rettype2,parameters2) \
275 _GL_EXTERN_C int _gl_cxxalias_dummy
276#endif
277
278/* _GL_CXXALIASWARN (func);
279 causes a warning to be emitted when ::func is used but not when
280 GNULIB_NAMESPACE::func is used. func must be defined without overloaded
281 variants. */
282#if defined __cplusplus && defined GNULIB_NAMESPACE
283# define _GL_CXXALIASWARN(func) \
284 _GL_CXXALIASWARN_1 (func, GNULIB_NAMESPACE)
285# define _GL_CXXALIASWARN_1(func,namespace) \
286 _GL_CXXALIASWARN_2 (func, namespace)
287/* To work around GCC bug <https://gcc.gnu.org/bugzilla/show_bug.cgi?id=43881>,
288 we enable the warning only when not optimizing. */
289# if !(defined __GNUC__ && !defined __clang__ && __OPTIMIZE__)
290# define _GL_CXXALIASWARN_2(func,namespace) \
291 _GL_WARN_ON_USE (func, \
292 "The symbol ::" #func " refers to the system function. " \
293 "Use " #namespace "::" #func " instead.")
294# elif __GNUC__ >= 3 && GNULIB_STRICT_CHECKING
295# define _GL_CXXALIASWARN_2(func,namespace) \
296 extern __typeof__ (func) func
297# else
298# define _GL_CXXALIASWARN_2(func,namespace) \
299 _GL_EXTERN_C int _gl_cxxalias_dummy
300# endif
301#else
302# define _GL_CXXALIASWARN(func) \
303 _GL_EXTERN_C int _gl_cxxalias_dummy
304#endif
305
306/* _GL_CXXALIASWARN1 (func, rettype, parameters_and_attributes);
307 causes a warning to be emitted when the given overloaded variant of ::func
308 is used but not when GNULIB_NAMESPACE::func is used. */
309#if defined __cplusplus && defined GNULIB_NAMESPACE
310# define _GL_CXXALIASWARN1(func,rettype,parameters_and_attributes) \
311 _GL_CXXALIASWARN1_1 (func, rettype, parameters_and_attributes, \
312 GNULIB_NAMESPACE)
313# define _GL_CXXALIASWARN1_1(func,rettype,parameters_and_attributes,namespace) \
314 _GL_CXXALIASWARN1_2 (func, rettype, parameters_and_attributes, namespace)
315/* To work around GCC bug <https://gcc.gnu.org/bugzilla/show_bug.cgi?id=43881>,
316 we enable the warning only when not optimizing. */
317# if !(defined __GNUC__ && !defined __clang__ && __OPTIMIZE__)
318# define _GL_CXXALIASWARN1_2(func,rettype,parameters_and_attributes,namespace) \
319 _GL_WARN_ON_USE_CXX (func, rettype, rettype, parameters_and_attributes, \
320 "The symbol ::" #func " refers to the system function. " \
321 "Use " #namespace "::" #func " instead.")
322# else
323# define _GL_CXXALIASWARN1_2(func,rettype,parameters_and_attributes,namespace) \
324 _GL_EXTERN_C int _gl_cxxalias_dummy
325# endif
326#else
327# define _GL_CXXALIASWARN1(func,rettype,parameters_and_attributes) \
328 _GL_EXTERN_C int _gl_cxxalias_dummy
329#endif
330
331#endif /* _GL_CXXDEFS_H */