/* Compile-time assert-like macros.
- Copyright (C) 2005, 2006 Free Software Foundation, Inc.
+ Copyright (C) 2005-2006, 2009-2011 Free Software Foundation, Inc.
- This program is free software; you can redistribute it and/or modify
+ This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
- the Free Software Foundation; either version 2, or (at your option)
- any later version.
+ the Free Software Foundation; either version 3 of the License, or
+ (at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
- along with this program; if not, write to the Free Software Foundation,
- Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA. */
+ along with this program. If not, see <http://www.gnu.org/licenses/>. */
/* Written by Paul Eggert, Bruno Haible, and Jim Meyering. */
#ifndef VERIFY_H
# define VERIFY_H 1
+/* Define HAVE__STATIC_ASSERT to 1 if _Static_assert works as per the
+ C1X draft N1548 section 6.7.10. This is supported by GCC 4.6.0 and
+ later, in C mode, and its use here generates easier-to-read diagnostics
+ when verify (R) fails.
+
+ Define HAVE_STATIC_ASSERT to 1 if static_assert works as per the
+ C1X draft N1548 section 7.2 or the C++0X draft N3242 section 7.(4).
+ This will likely be supported by future GCC versions, in C++ mode.
+
+ For now, use this only with GCC. Eventually whether _Static_assert
+ and static_assert works should be determined by 'configure'. */
+# if (4 < __GNUC__ || (__GNUC__ == 4 && 6 <= __GNUC_MINOR__)) && !defined __cplusplus
+# define HAVE__STATIC_ASSERT 1
+# endif
+/* The condition (99 < __GNUC__) is temporary, until we know about the
+ first G++ release that supports static_assert. */
+# if (99 < __GNUC__) && defined __cplusplus
+# define HAVE_STATIC_ASSERT 1
+# endif
+
/* Each of these macros verifies that its argument R is nonzero. To
be portable, R should be an integer constant expression. Unlike
assert (R), there is no run-time overhead.
Symbols ending in "__" are private to this header.
- The code below uses several ideas.
+ If _Static_assert works, verify (R) uses it directly. Similarly,
+ verify_true (R) works by packaging a _Static_assert inside a struct
+ that is an operand of sizeof.
+
+ The code below uses several ideas for C++ compilers, and for C
+ compilers that do not support _Static_assert:
* The first step is ((R) ? 1 : -1). Given an expression R, of
integral or boolean or floating-point type, this yields an
if the entity names are not disambiguated. A workaround is to
attach the current line number to the entity name:
- #define GL_CONCAT0(x, y) x##y
- #define GL_CONCAT(x, y) GL_CONCAT0 (x, y)
- extern struct {...} * GL_CONCAT(dummy,__LINE__);
+ #define _GL_CONCAT0(x, y) x##y
+ #define _GL_CONCAT(x, y) _GL_CONCAT0 (x, y)
+ extern struct {...} * _GL_CONCAT (dummy, __LINE__);
But this has the problem that two invocations of verify from
within the same macro would collide, since the __LINE__ value
- would be the same for both invocations.
+ would be the same for both invocations. (The GCC __COUNTER__
+ macro solves this problem, but is not portable.)
A solution is to use the sizeof operator. It yields a number,
getting rid of the identity of the type. Declarations like
extern int (*dummy (void)) [sizeof (struct {...})];
- * This implementation exploits the fact that GCC does not warn about
- the last declaration mentioned above. If a future version of GCC
- introduces a warning for this, the problem could be worked around
- by using code specialized to GCC, e.g.,:
+ * GCC warns about duplicate declarations of the dummy function if
+ -Wredundant_decls is used. GCC 4.3 and later have a builtin
+ __COUNTER__ macro that can let us generate unique identifiers for
+ each dummy function, to suppress this warning.
- #if 4 <= __GNUC__
- # define verify(R) \
- extern int (* verify_function__ (void)) \
- [__builtin_constant_p (R) && (R) ? 1 : -1]
- #endif
+ * This implementation exploits the fact that older versions of GCC,
+ which do not support _Static_assert, also do not warn about the
+ last declaration mentioned above.
* In C++, any struct definition inside sizeof is invalid.
Use a template type to work around the problem. */
+/* Concatenate two preprocessor tokens. */
+# define _GL_CONCAT(x, y) _GL_CONCAT0 (x, y)
+# define _GL_CONCAT0(x, y) x##y
+
+/* _GL_COUNTER is an integer, preferably one that changes each time we
+ use it. Use __COUNTER__ if it works, falling back on __LINE__
+ otherwise. __LINE__ isn't perfect, but it's better than a
+ constant. */
+# if defined __COUNTER__ && __COUNTER__ != __COUNTER__
+# define _GL_COUNTER __COUNTER__
+# else
+# define _GL_COUNTER __LINE__
+# endif
+
+/* Generate a symbol with the given prefix, making it unique if
+ possible. */
+# define _GL_GENSYM(prefix) _GL_CONCAT (prefix, _GL_COUNTER)
/* Verify requirement R at compile-time, as an integer constant expression.
Return 1. */
struct verify_type__ { unsigned int verify_error_if_negative_size__: w; };
# define verify_true(R) \
(!!sizeof (verify_type__<(R) ? 1 : -1>))
+# elif HAVE__STATIC_ASSERT
+# define verify_true(R) \
+ (!!sizeof \
+ (struct { \
+ _Static_assert (R, "verify_true (" #R ")"); \
+ int verify_dummy__; \
+ }))
+# elif HAVE_STATIC_ASSERT
+# define verify_true(R) \
+ (!!sizeof \
+ (struct { \
+ static_assert (R, "verify_true (" #R ")"); \
+ int verify_dummy__; \
+ }))
# else
# define verify_true(R) \
(!!sizeof \
/* Verify requirement R at compile-time, as a declaration without a
trailing ';'. */
-# define verify(R) extern int (* verify_function__ (void)) [verify_true (R)]
+# if HAVE__STATIC_ASSERT
+# define verify(R) _Static_assert (R, "verify (" #R ")")
+# elif HAVE_STATIC_ASSERT
+# define verify(R) static_assert (R, "verify (" #R ")")
+# else
+# define verify(R) \
+ extern int (* _GL_GENSYM (verify_function) (void)) [verify_true (R)]
+# endif
#endif
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