X-Git-Url: https://git.notmuchmail.org/git?a=blobdiff_plain;f=lib%2Fverify.h;fp=lib%2Fverify.h;h=0000000000000000000000000000000000000000;hb=22f1eb8bc17e5be72dd23d42d6aaa60196ac22e6;hp=fac53f6fc4ac94e4452f9d1ee63712dd3d04c14f;hpb=00fa13ff3f2d5b6e2a94c5e948c38616ff7ad37a;p=tar diff --git a/lib/verify.h b/lib/verify.h deleted file mode 100644 index fac53f6..0000000 --- a/lib/verify.h +++ /dev/null @@ -1,140 +0,0 @@ -/* Compile-time assert-like macros. - - Copyright (C) 2005, 2006 Free Software Foundation, Inc. - - 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 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 - MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the - 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, see . */ - -/* 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. - - 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 {...})]; - - * 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.,: - - #if 4 <= __GNUC__ - # define verify(R) \ - extern int (* verify_function__ (void)) \ - [__builtin_constant_p (R) && (R) ? 1 : -1] - #endif - - * In C++, any struct definition inside sizeof is invalid. - Use a template type to work around the problem. */ - - -/* Verify requirement R at compile-time, as an integer constant expression. - Return 1. */ - -# ifdef __cplusplus -template - 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 (* verify_function__ (void)) [verify_true (R)] - -#endif