| Index: bison/src/bison/2.4.1/bison-2.4.1-src/lib/verify.h
|
| ===================================================================
|
| --- bison/src/bison/2.4.1/bison-2.4.1-src/lib/verify.h (revision 0)
|
| +++ bison/src/bison/2.4.1/bison-2.4.1-src/lib/verify.h (revision 0)
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| @@ -0,0 +1,140 @@
|
| +/* 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 <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
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| + 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:
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| +
|
| + 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 <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 (* verify_function__ (void)) [verify_true (R)]
|
| +
|
| +#endif
|
|
|
| Property changes on: bison\src\bison\2.4.1\bison-2.4.1-src\lib\verify.h
|
| ___________________________________________________________________
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| Added: svn:eol-style
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