1 /* -*- buffer-read-only: t -*- vi: set ro: */
2 /* DO NOT EDIT! GENERATED AUTOMATICALLY! */
3 /* Compile-time assert-like macros.
5 Copyright (C) 2005-2006, 2009-2014 Free Software Foundation, Inc.
7 This program is free software: you can redistribute it and/or modify
8 it under the terms of the GNU General Public License as published by
9 the Free Software Foundation; either version 3 of the License, or
10 (at your option) any later version.
12 This program is distributed in the hope that it will be useful,
13 but WITHOUT ANY WARRANTY; without even the implied warranty of
14 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
15 GNU General Public License for more details.
17 You should have received a copy of the GNU General Public License
18 along with this program. If not, see <http://www.gnu.org/licenses/>. */
20 /* Written by Paul Eggert, Bruno Haible, and Jim Meyering. */
26 /* Define _GL_HAVE__STATIC_ASSERT to 1 if _Static_assert works as per C11.
27 This is supported by GCC 4.6.0 and later, in C mode, and its use
28 here generates easier-to-read diagnostics when verify (R) fails.
30 Define _GL_HAVE_STATIC_ASSERT to 1 if static_assert works as per C++11.
31 This will likely be supported by future GCC versions, in C++ mode.
33 Use this only with GCC. If we were willing to slow 'configure'
34 down we could also use it with other compilers, but since this
35 affects only the quality of diagnostics, why bother? */
36 #if (4 < __GNUC__ + (6 <= __GNUC_MINOR__) \
37 && (201112L <= __STDC_VERSION__ || !defined __STRICT_ANSI__) \
38 && !defined __cplusplus)
39 # define _GL_HAVE__STATIC_ASSERT 1
41 /* The condition (99 < __GNUC__) is temporary, until we know about the
42 first G++ release that supports static_assert. */
43 #if (99 < __GNUC__) && defined __cplusplus
44 # define _GL_HAVE_STATIC_ASSERT 1
47 /* FreeBSD 9.1 <sys/cdefs.h>, included by <stddef.h> and lots of other
48 system headers, defines a conflicting _Static_assert that is no
49 better than ours; override it. */
50 #ifndef _GL_HAVE_STATIC_ASSERT
52 # undef _Static_assert
55 /* Each of these macros verifies that its argument R is nonzero. To
56 be portable, R should be an integer constant expression. Unlike
57 assert (R), there is no run-time overhead.
59 If _Static_assert works, verify (R) uses it directly. Similarly,
60 _GL_VERIFY_TRUE works by packaging a _Static_assert inside a struct
61 that is an operand of sizeof.
63 The code below uses several ideas for C++ compilers, and for C
64 compilers that do not support _Static_assert:
66 * The first step is ((R) ? 1 : -1). Given an expression R, of
67 integral or boolean or floating-point type, this yields an
68 expression of integral type, whose value is later verified to be
69 constant and nonnegative.
71 * Next this expression W is wrapped in a type
72 struct _gl_verify_type {
73 unsigned int _gl_verify_error_if_negative: W;
75 If W is negative, this yields a compile-time error. No compiler can
76 deal with a bit-field of negative size.
78 One might think that an array size check would have the same
79 effect, that is, that the type struct { unsigned int dummy[W]; }
80 would work as well. However, inside a function, some compilers
81 (such as C++ compilers and GNU C) allow local parameters and
82 variables inside array size expressions. With these compilers,
83 an array size check would not properly diagnose this misuse of
86 void function (int n) { verify (n < 0); }
88 * For the verify macro, the struct _gl_verify_type will need to
89 somehow be embedded into a declaration. To be portable, this
90 declaration must declare an object, a constant, a function, or a
91 typedef name. If the declared entity uses the type directly,
95 typedef struct {...} dummy;
96 extern struct {...} *dummy;
97 extern void dummy (struct {...} *);
98 extern struct {...} *dummy (void);
100 two uses of the verify macro would yield colliding declarations
101 if the entity names are not disambiguated. A workaround is to
102 attach the current line number to the entity name:
104 #define _GL_CONCAT0(x, y) x##y
105 #define _GL_CONCAT(x, y) _GL_CONCAT0 (x, y)
106 extern struct {...} * _GL_CONCAT (dummy, __LINE__);
108 But this has the problem that two invocations of verify from
109 within the same macro would collide, since the __LINE__ value
110 would be the same for both invocations. (The GCC __COUNTER__
111 macro solves this problem, but is not portable.)
113 A solution is to use the sizeof operator. It yields a number,
114 getting rid of the identity of the type. Declarations like
116 extern int dummy [sizeof (struct {...})];
117 extern void dummy (int [sizeof (struct {...})]);
118 extern int (*dummy (void)) [sizeof (struct {...})];
122 * Should the implementation use a named struct or an unnamed struct?
123 Which of the following alternatives can be used?
125 extern int dummy [sizeof (struct {...})];
126 extern int dummy [sizeof (struct _gl_verify_type {...})];
127 extern void dummy (int [sizeof (struct {...})]);
128 extern void dummy (int [sizeof (struct _gl_verify_type {...})]);
129 extern int (*dummy (void)) [sizeof (struct {...})];
130 extern int (*dummy (void)) [sizeof (struct _gl_verify_type {...})];
132 In the second and sixth case, the struct type is exported to the
133 outer scope; two such declarations therefore collide. GCC warns
134 about the first, third, and fourth cases. So the only remaining
135 possibility is the fifth case:
137 extern int (*dummy (void)) [sizeof (struct {...})];
139 * GCC warns about duplicate declarations of the dummy function if
140 -Wredundant-decls is used. GCC 4.3 and later have a builtin
141 __COUNTER__ macro that can let us generate unique identifiers for
142 each dummy function, to suppress this warning.
144 * This implementation exploits the fact that older versions of GCC,
145 which do not support _Static_assert, also do not warn about the
146 last declaration mentioned above.
148 * GCC warns if -Wnested-externs is enabled and verify() is used
149 within a function body; but inside a function, you can always
150 arrange to use verify_expr() instead.
152 * In C++, any struct definition inside sizeof is invalid.
153 Use a template type to work around the problem. */
155 /* Concatenate two preprocessor tokens. */
156 #define _GL_CONCAT(x, y) _GL_CONCAT0 (x, y)
157 #define _GL_CONCAT0(x, y) x##y
159 /* _GL_COUNTER is an integer, preferably one that changes each time we
160 use it. Use __COUNTER__ if it works, falling back on __LINE__
161 otherwise. __LINE__ isn't perfect, but it's better than a
163 #if defined __COUNTER__ && __COUNTER__ != __COUNTER__
164 # define _GL_COUNTER __COUNTER__
166 # define _GL_COUNTER __LINE__
169 /* Generate a symbol with the given prefix, making it unique if
171 #define _GL_GENSYM(prefix) _GL_CONCAT (prefix, _GL_COUNTER)
173 /* Verify requirement R at compile-time, as an integer constant expression
174 that returns 1. If R is false, fail at compile-time, preferably
175 with a diagnostic that includes the string-literal DIAGNOSTIC. */
177 #define _GL_VERIFY_TRUE(R, DIAGNOSTIC) \
178 (!!sizeof (_GL_VERIFY_TYPE (R, DIAGNOSTIC)))
181 # if !GNULIB_defined_struct__gl_verify_type
183 struct _gl_verify_type {
184 unsigned int _gl_verify_error_if_negative: w;
186 # define GNULIB_defined_struct__gl_verify_type 1
188 # define _GL_VERIFY_TYPE(R, DIAGNOSTIC) \
189 _gl_verify_type<(R) ? 1 : -1>
190 #elif defined _GL_HAVE__STATIC_ASSERT
191 # define _GL_VERIFY_TYPE(R, DIAGNOSTIC) \
193 _Static_assert (R, DIAGNOSTIC); \
197 # define _GL_VERIFY_TYPE(R, DIAGNOSTIC) \
198 struct { unsigned int _gl_verify_error_if_negative: (R) ? 1 : -1; }
201 /* Verify requirement R at compile-time, as a declaration without a
202 trailing ';'. If R is false, fail at compile-time, preferably
203 with a diagnostic that includes the string-literal DIAGNOSTIC.
205 Unfortunately, unlike C11, this implementation must appear as an
206 ordinary declaration, and cannot appear inside struct { ... }. */
208 #ifdef _GL_HAVE__STATIC_ASSERT
209 # define _GL_VERIFY _Static_assert
211 # define _GL_VERIFY(R, DIAGNOSTIC) \
212 extern int (*_GL_GENSYM (_gl_verify_function) (void)) \
213 [_GL_VERIFY_TRUE (R, DIAGNOSTIC)]
216 /* _GL_STATIC_ASSERT_H is defined if this code is copied into assert.h. */
217 #ifdef _GL_STATIC_ASSERT_H
218 # if !defined _GL_HAVE__STATIC_ASSERT && !defined _Static_assert
219 # define _Static_assert(R, DIAGNOSTIC) _GL_VERIFY (R, DIAGNOSTIC)
221 # if !defined _GL_HAVE_STATIC_ASSERT && !defined static_assert
222 # define static_assert _Static_assert /* C11 requires this #define. */
226 /* @assert.h omit start@ */
228 /* Each of these macros verifies that its argument R is nonzero. To
229 be portable, R should be an integer constant expression. Unlike
230 assert (R), there is no run-time overhead.
232 There are two macros, since no single macro can be used in all
233 contexts in C. verify_true (R) is for scalar contexts, including
234 integer constant expression contexts. verify (R) is for declaration
235 contexts, e.g., the top level. */
237 /* Verify requirement R at compile-time, as an integer constant expression.
238 Return 1. This is equivalent to verify_expr (R, 1).
240 verify_true is obsolescent; please use verify_expr instead. */
242 #define verify_true(R) _GL_VERIFY_TRUE (R, "verify_true (" #R ")")
244 /* Verify requirement R at compile-time. Return the value of the
247 #define verify_expr(R, E) \
248 (_GL_VERIFY_TRUE (R, "verify_expr (" #R ", " #E ")") ? (E) : (E))
250 /* Verify requirement R at compile-time, as a declaration without a
253 #define verify(R) _GL_VERIFY (R, "verify (" #R ")")
255 #ifndef __has_builtin
256 # define __has_builtin(x) 0
259 /* Assume that R always holds. This lets the compiler optimize
260 accordingly. R should not have side-effects; it may or may not be
261 evaluated. Behavior is undefined if R is false. */
263 #if (__has_builtin (__builtin_unreachable) \
264 || 4 < __GNUC__ + (5 <= __GNUC_MINOR__))
265 # define assume(R) ((R) ? (void) 0 : __builtin_unreachable ())
266 #elif 1200 <= _MSC_VER
267 # define assume(R) __assume (R)
268 #elif (defined lint \
269 && (__has_builtin (__builtin_trap) \
270 || 3 < __GNUC__ + (3 < __GNUC_MINOR__ + (4 <= __GNUC_PATCHLEVEL__))))
271 /* Doing it this way helps various packages when configured with
272 --enable-gcc-warnings, which compiles with -Dlint. It's nicer
273 when 'assume' silences warnings even with older GCCs. */
274 # define assume(R) ((R) ? (void) 0 : __builtin_trap ())
276 # define assume(R) ((void) (0 && (R)))
279 /* @assert.h omit end@ */