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Diffstat (limited to 'lib/gl/verify.h')
| -rw-r--r-- | lib/gl/verify.h | 163 |
1 files changed, 0 insertions, 163 deletions
diff --git a/lib/gl/verify.h b/lib/gl/verify.h deleted file mode 100644 index a29f8666df..0000000000 --- a/lib/gl/verify.h +++ /dev/null @@ -1,163 +0,0 @@ -/* Compile-time assert-like macros. - - Copyright (C) 2005-2006, 2009-2010 Free Software Foundation, Inc. - - This program is free software: you can redistribute it and/or modify - it under the terms of the GNU Lesser General Public License as published by - the Free Software Foundation; either version 2.1 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 - MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the - GNU Lesser General Public License for more details. - - You should have received a copy of the GNU Lesser General Public License - 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 - -/* 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. - - There are two macros, since no single macro can be used in all - contexts in C. verify_true (R) is for scalar contexts, including - integer constant expression contexts. verify (R) is for declaration - contexts, e.g., the top level. - - Symbols ending in "__" are private to this header. - - The code below uses several ideas. - - * The first step is ((R) ? 1 : -1). Given an expression R, of - integral or boolean or floating-point type, this yields an - expression of integral type, whose value is later verified to be - constant and nonnegative. - - * Next this expression W is wrapped in a type - struct verify_type__ { unsigned int verify_error_if_negative_size__: W; }. - If W is negative, this yields a compile-time error. No compiler can - deal with a bit-field of negative size. - - One might think that an array size check would have the same - effect, that is, that the type struct { unsigned int dummy[W]; } - would work as well. However, inside a function, some compilers - (such as C++ compilers and GNU C) allow local parameters and - variables inside array size expressions. With these compilers, - an array size check would not properly diagnose this misuse of - the verify macro: - - void function (int n) { verify (n < 0); } - - * For the verify macro, the struct verify_type__ will need to - somehow be embedded into a declaration. To be portable, this - declaration must declare an object, a constant, a function, or a - typedef name. If the declared entity uses the type directly, - such as in - - struct dummy {...}; - typedef struct {...} dummy; - extern struct {...} *dummy; - extern void dummy (struct {...} *); - extern struct {...} *dummy (void); - - two uses of the verify macro would yield colliding declarations - 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__); - - 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. (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 [sizeof (struct {...})]; - extern void dummy (int [sizeof (struct {...})]); - extern int (*dummy (void)) [sizeof (struct {...})]; - - can be repeated. - - * Should the implementation use a named struct or an unnamed struct? - Which of the following alternatives can be used? - - extern int dummy [sizeof (struct {...})]; - extern int dummy [sizeof (struct verify_type__ {...})]; - extern void dummy (int [sizeof (struct {...})]); - extern void dummy (int [sizeof (struct verify_type__ {...})]); - extern int (*dummy (void)) [sizeof (struct {...})]; - extern int (*dummy (void)) [sizeof (struct verify_type__ {...})]; - - In the second and sixth case, the struct type is exported to the - outer scope; two such declarations therefore collide. GCC warns - about the first, third, and fourth cases. So the only remaining - possibility is the fifth case: - - extern int (*dummy (void)) [sizeof (struct {...})]; - - * 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. - - * 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, just as __COUNTER__ is already - being used if available. - - #if 4 <= __GNUC__ - # define verify(R) [another version to keep GCC happy] - #endif - - * 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. */ - -# ifdef __cplusplus -template <int w> - struct verify_type__ { unsigned int verify_error_if_negative_size__: w; }; -# define verify_true(R) \ - (!!sizeof (verify_type__<(R) ? 1 : -1>)) -# else -# define verify_true(R) \ - (!!sizeof \ - (struct { unsigned int verify_error_if_negative_size__: (R) ? 1 : -1; })) -# endif - -/* Verify requirement R at compile-time, as a declaration without a - trailing ';'. */ - -# define verify(R) \ - extern int (* _GL_GENSYM (verify_function) (void)) [verify_true (R)] - -#endif |