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, 2009-2013 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 /* Each of these macros verifies that its argument R is nonzero. To
48 be portable, R should be an integer constant expression. Unlike
49 assert (R), there is no run-time overhead.
51 If _Static_assert works, verify (R) uses it directly. Similarly,
52 _GL_VERIFY_TRUE works by packaging a _Static_assert inside a struct
53 that is an operand of sizeof.
55 The code below uses several ideas for C++ compilers, and for C
56 compilers that do not support _Static_assert:
58 * The first step is ((R) ? 1 : -1). Given an expression R, of
59 integral or boolean or floating-point type, this yields an
60 expression of integral type, whose value is later verified to be
61 constant and nonnegative.
63 * Next this expression W is wrapped in a type
64 struct _gl_verify_type {
65 unsigned int _gl_verify_error_if_negative: W;
67 If W is negative, this yields a compile-time error. No compiler can
68 deal with a bit-field of negative size.
70 One might think that an array size check would have the same
71 effect, that is, that the type struct { unsigned int dummy[W]; }
72 would work as well. However, inside a function, some compilers
73 (such as C++ compilers and GNU C) allow local parameters and
74 variables inside array size expressions. With these compilers,
75 an array size check would not properly diagnose this misuse of
78 void function (int n) { verify (n < 0); }
80 * For the verify macro, the struct _gl_verify_type will need to
81 somehow be embedded into a declaration. To be portable, this
82 declaration must declare an object, a constant, a function, or a
83 typedef name. If the declared entity uses the type directly,
87 typedef struct {...} dummy;
88 extern struct {...} *dummy;
89 extern void dummy (struct {...} *);
90 extern struct {...} *dummy (void);
92 two uses of the verify macro would yield colliding declarations
93 if the entity names are not disambiguated. A workaround is to
94 attach the current line number to the entity name:
96 #define _GL_CONCAT0(x, y) x##y
97 #define _GL_CONCAT(x, y) _GL_CONCAT0 (x, y)
98 extern struct {...} * _GL_CONCAT (dummy, __LINE__);
100 But this has the problem that two invocations of verify from
101 within the same macro would collide, since the __LINE__ value
102 would be the same for both invocations. (The GCC __COUNTER__
103 macro solves this problem, but is not portable.)
105 A solution is to use the sizeof operator. It yields a number,
106 getting rid of the identity of the type. Declarations like
108 extern int dummy [sizeof (struct {...})];
109 extern void dummy (int [sizeof (struct {...})]);
110 extern int (*dummy (void)) [sizeof (struct {...})];
114 * Should the implementation use a named struct or an unnamed struct?
115 Which of the following alternatives can be used?
117 extern int dummy [sizeof (struct {...})];
118 extern int dummy [sizeof (struct _gl_verify_type {...})];
119 extern void dummy (int [sizeof (struct {...})]);
120 extern void dummy (int [sizeof (struct _gl_verify_type {...})]);
121 extern int (*dummy (void)) [sizeof (struct {...})];
122 extern int (*dummy (void)) [sizeof (struct _gl_verify_type {...})];
124 In the second and sixth case, the struct type is exported to the
125 outer scope; two such declarations therefore collide. GCC warns
126 about the first, third, and fourth cases. So the only remaining
127 possibility is the fifth case:
129 extern int (*dummy (void)) [sizeof (struct {...})];
131 * GCC warns about duplicate declarations of the dummy function if
132 -Wredundant-decls is used. GCC 4.3 and later have a builtin
133 __COUNTER__ macro that can let us generate unique identifiers for
134 each dummy function, to suppress this warning.
136 * This implementation exploits the fact that older versions of GCC,
137 which do not support _Static_assert, also do not warn about the
138 last declaration mentioned above.
140 * GCC warns if -Wnested-externs is enabled and verify() is used
141 within a function body; but inside a function, you can always
142 arrange to use verify_expr() instead.
144 * In C++, any struct definition inside sizeof is invalid.
145 Use a template type to work around the problem. */
147 /* Concatenate two preprocessor tokens. */
148 # define _GL_CONCAT(x, y) _GL_CONCAT0 (x, y)
149 # define _GL_CONCAT0(x, y) x##y
151 /* _GL_COUNTER is an integer, preferably one that changes each time we
152 use it. Use __COUNTER__ if it works, falling back on __LINE__
153 otherwise. __LINE__ isn't perfect, but it's better than a
155 # if defined __COUNTER__ && __COUNTER__ != __COUNTER__
156 # define _GL_COUNTER __COUNTER__
158 # define _GL_COUNTER __LINE__
161 /* Generate a symbol with the given prefix, making it unique if
163 # define _GL_GENSYM(prefix) _GL_CONCAT (prefix, _GL_COUNTER)
165 /* Verify requirement R at compile-time, as an integer constant expression
166 that returns 1. If R is false, fail at compile-time, preferably
167 with a diagnostic that includes the string-literal DIAGNOSTIC. */
169 # define _GL_VERIFY_TRUE(R, DIAGNOSTIC) \
170 (!!sizeof (_GL_VERIFY_TYPE (R, DIAGNOSTIC)))
173 # if !GNULIB_defined_struct__gl_verify_type
175 struct _gl_verify_type {
176 unsigned int _gl_verify_error_if_negative: w;
178 # define GNULIB_defined_struct__gl_verify_type 1
180 # define _GL_VERIFY_TYPE(R, DIAGNOSTIC) \
181 _gl_verify_type<(R) ? 1 : -1>
182 # elif defined _GL_HAVE__STATIC_ASSERT
183 # define _GL_VERIFY_TYPE(R, DIAGNOSTIC) \
185 _Static_assert (R, DIAGNOSTIC); \
189 # define _GL_VERIFY_TYPE(R, DIAGNOSTIC) \
190 struct { unsigned int _gl_verify_error_if_negative: (R) ? 1 : -1; }
193 /* Verify requirement R at compile-time, as a declaration without a
194 trailing ';'. If R is false, fail at compile-time, preferably
195 with a diagnostic that includes the string-literal DIAGNOSTIC.
197 Unfortunately, unlike C11, this implementation must appear as an
198 ordinary declaration, and cannot appear inside struct { ... }. */
200 # ifdef _GL_HAVE__STATIC_ASSERT
201 # define _GL_VERIFY _Static_assert
203 # define _GL_VERIFY(R, DIAGNOSTIC) \
204 extern int (*_GL_GENSYM (_gl_verify_function) (void)) \
205 [_GL_VERIFY_TRUE (R, DIAGNOSTIC)]
208 /* _GL_STATIC_ASSERT_H is defined if this code is copied into assert.h. */
209 # ifdef _GL_STATIC_ASSERT_H
210 # if !defined _GL_HAVE__STATIC_ASSERT && !defined _Static_assert
211 # define _Static_assert(R, DIAGNOSTIC) _GL_VERIFY (R, DIAGNOSTIC)
213 # if !defined _GL_HAVE_STATIC_ASSERT && !defined static_assert
214 # define static_assert _Static_assert /* C11 requires this #define. */
218 /* @assert.h omit start@ */
220 /* Each of these macros verifies that its argument R is nonzero. To
221 be portable, R should be an integer constant expression. Unlike
222 assert (R), there is no run-time overhead.
224 There are two macros, since no single macro can be used in all
225 contexts in C. verify_true (R) is for scalar contexts, including
226 integer constant expression contexts. verify (R) is for declaration
227 contexts, e.g., the top level. */
229 /* Verify requirement R at compile-time, as an integer constant expression.
230 Return 1. This is equivalent to verify_expr (R, 1).
232 verify_true is obsolescent; please use verify_expr instead. */
234 # define verify_true(R) _GL_VERIFY_TRUE (R, "verify_true (" #R ")")
236 /* Verify requirement R at compile-time. Return the value of the
239 # define verify_expr(R, E) \
240 (_GL_VERIFY_TRUE (R, "verify_expr (" #R ", " #E ")") ? (E) : (E))
242 /* Verify requirement R at compile-time, as a declaration without a
245 # define verify(R) _GL_VERIFY (R, "verify (" #R ")")
247 /* @assert.h omit end@ */