diff options
Diffstat (limited to 'lib/verify.h')
| -rw-r--r-- | lib/verify.h | 217 |
1 files changed, 39 insertions, 178 deletions
diff --git a/lib/verify.h b/lib/verify.h index db52900e..7773c794 100644 --- a/lib/verify.h +++ b/lib/verify.h @@ -1,6 +1,6 @@ /* Compile-time assert-like macros. - Copyright (C) 2005-2006, 2009-2015 Free Software Foundation, Inc. + 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 @@ -17,49 +17,21 @@ /* Written by Paul Eggert, Bruno Haible, and Jim Meyering. */ -#ifndef _GL_VERIFY_H -#define _GL_VERIFY_H - - -/* Define _GL_HAVE__STATIC_ASSERT to 1 if _Static_assert works as per C11. - 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 _GL_HAVE_STATIC_ASSERT to 1 if static_assert works as per C++11. - This will likely be supported by future GCC versions, in C++ mode. - - Use this only with GCC. If we were willing to slow 'configure' - down we could also use it with other compilers, but since this - affects only the quality of diagnostics, why bother? */ -#if (4 < __GNUC__ + (6 <= __GNUC_MINOR__) \ - && (201112L <= __STDC_VERSION__ || !defined __STRICT_ANSI__) \ - && !defined __cplusplus) -# define _GL_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 _GL_HAVE_STATIC_ASSERT 1 -#endif - -/* FreeBSD 9.1 <sys/cdefs.h>, included by <stddef.h> and lots of other - system headers, defines a conflicting _Static_assert that is no - better than ours; override it. */ -#ifndef _GL_HAVE_STATIC_ASSERT -# include <stddef.h> -# undef _Static_assert -#endif +#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. - If _Static_assert works, verify (R) uses it directly. Similarly, - _GL_VERIFY_TRUE works by packaging a _Static_assert inside a struct - that is an operand of sizeof. + 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 for C++ compilers, and for C - compilers that do not support _Static_assert: + 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 @@ -67,9 +39,7 @@ constant and nonnegative. * Next this expression W is wrapped in a type - struct _gl_verify_type { - unsigned int _gl_verify_error_if_negative: W; - }. + 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. @@ -83,7 +53,7 @@ void function (int n) { verify (n < 0); } - * For the verify macro, the struct _gl_verify_type will need to + * 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, @@ -99,14 +69,13 @@ 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. (The GCC __COUNTER__ - macro solves this problem, but is not portable.) + 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 @@ -121,11 +90,11 @@ Which of the following alternatives can be used? extern int dummy [sizeof (struct {...})]; - extern int dummy [sizeof (struct _gl_verify_type {...})]; + extern int dummy [sizeof (struct verify_type__ {...})]; extern void dummy (int [sizeof (struct {...})]); - extern void dummy (int [sizeof (struct _gl_verify_type {...})]); + extern void dummy (int [sizeof (struct verify_type__ {...})]); extern int (*dummy (void)) [sizeof (struct {...})]; - extern int (*dummy (void)) [sizeof (struct _gl_verify_type {...})]; + 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 @@ -134,146 +103,38 @@ 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, e.g.,: - * 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. - - * GCC warns if -Wnested-externs is enabled and verify() is used - within a function body; but inside a function, you can always - arrange to use verify_expr() instead. + #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. */ -/* 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 - that returns 1. If R is false, fail at compile-time, preferably - with a diagnostic that includes the string-literal DIAGNOSTIC. */ - -#define _GL_VERIFY_TRUE(R, DIAGNOSTIC) \ - (!!sizeof (_GL_VERIFY_TYPE (R, DIAGNOSTIC))) +/* Verify requirement R at compile-time, as an integer constant expression. + Return 1. */ -#ifdef __cplusplus -# if !GNULIB_defined_struct__gl_verify_type +# ifdef __cplusplus template <int w> - struct _gl_verify_type { - unsigned int _gl_verify_error_if_negative: w; - }; -# define GNULIB_defined_struct__gl_verify_type 1 + 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 -# define _GL_VERIFY_TYPE(R, DIAGNOSTIC) \ - _gl_verify_type<(R) ? 1 : -1> -#elif defined _GL_HAVE__STATIC_ASSERT -# define _GL_VERIFY_TYPE(R, DIAGNOSTIC) \ - struct { \ - _Static_assert (R, DIAGNOSTIC); \ - int _gl_dummy; \ - } -#else -# define _GL_VERIFY_TYPE(R, DIAGNOSTIC) \ - struct { unsigned int _gl_verify_error_if_negative: (R) ? 1 : -1; } -#endif - -/* Verify requirement R at compile-time, as a declaration without a - trailing ';'. If R is false, fail at compile-time, preferably - with a diagnostic that includes the string-literal DIAGNOSTIC. - - Unfortunately, unlike C11, this implementation must appear as an - ordinary declaration, and cannot appear inside struct { ... }. */ - -#ifdef _GL_HAVE__STATIC_ASSERT -# define _GL_VERIFY _Static_assert -#else -# define _GL_VERIFY(R, DIAGNOSTIC) \ - extern int (*_GL_GENSYM (_gl_verify_function) (void)) \ - [_GL_VERIFY_TRUE (R, DIAGNOSTIC)] -#endif - -/* _GL_STATIC_ASSERT_H is defined if this code is copied into assert.h. */ -#ifdef _GL_STATIC_ASSERT_H -# if !defined _GL_HAVE__STATIC_ASSERT && !defined _Static_assert -# define _Static_assert(R, DIAGNOSTIC) _GL_VERIFY (R, DIAGNOSTIC) -# endif -# if !defined _GL_HAVE_STATIC_ASSERT && !defined static_assert -# define static_assert _Static_assert /* C11 requires this #define. */ -# endif -#endif - -/* @assert.h omit start@ */ - -/* 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. */ - -/* Verify requirement R at compile-time, as an integer constant expression. - Return 1. This is equivalent to verify_expr (R, 1). - - verify_true is obsolescent; please use verify_expr instead. */ - -#define verify_true(R) _GL_VERIFY_TRUE (R, "verify_true (" #R ")") - -/* Verify requirement R at compile-time. Return the value of the - expression E. */ - -#define verify_expr(R, E) \ - (_GL_VERIFY_TRUE (R, "verify_expr (" #R ", " #E ")") ? (E) : (E)) /* Verify requirement R at compile-time, as a declaration without a trailing ';'. */ -#define verify(R) _GL_VERIFY (R, "verify (" #R ")") - -#ifndef __has_builtin -# define __has_builtin(x) 0 -#endif - -/* Assume that R always holds. This lets the compiler optimize - accordingly. R should not have side-effects; it may or may not be - evaluated. Behavior is undefined if R is false. */ - -#if (__has_builtin (__builtin_unreachable) \ - || 4 < __GNUC__ + (5 <= __GNUC_MINOR__)) -# define assume(R) ((R) ? (void) 0 : __builtin_unreachable ()) -#elif 1200 <= _MSC_VER -# define assume(R) __assume (R) -#elif (defined lint \ - && (__has_builtin (__builtin_trap) \ - || 3 < __GNUC__ + (3 < __GNUC_MINOR__ + (4 <= __GNUC_PATCHLEVEL__)))) - /* Doing it this way helps various packages when configured with - --enable-gcc-warnings, which compiles with -Dlint. It's nicer - when 'assume' silences warnings even with older GCCs. */ -# define assume(R) ((R) ? (void) 0 : __builtin_trap ()) -#else -# define assume(R) ((void) (0 && (R))) -#endif - -/* @assert.h omit end@ */ +# define verify(R) extern int (* verify_function__ (void)) [verify_true (R)] #endif |