diff options
| -rw-r--r-- | lib/verify.h | 130 |
1 files changed, 79 insertions, 51 deletions
diff --git a/lib/verify.h b/lib/verify.h index 6bca43f6a9b..e5065ffa00b 100644 --- a/lib/verify.h +++ b/lib/verify.h @@ -17,42 +17,37 @@ /* Written by Paul Eggert, Bruno Haible, and Jim Meyering. */ -#ifndef VERIFY_H -# define VERIFY_H 1 +#ifndef _GL_VERIFY_H +# define _GL_VERIFY_H -/* Define HAVE__STATIC_ASSERT to 1 if _Static_assert works as per the + +/* Define _GL_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). + Define _GL_HAVE_STATIC_ASSERT to 1 if static_assert works as per 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'. */ + 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__ || (__GNUC__ == 4 && 6 <= __GNUC_MINOR__)) && !defined __cplusplus -# define HAVE__STATIC_ASSERT 1 +# 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 HAVE_STATIC_ASSERT 1 +# define _GL_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. - 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. - If _Static_assert works, verify (R) uses it directly. Similarly, - verify_true (R) works by packaging a _Static_assert inside a struct + _GL_VERIFY_TRUE 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 @@ -64,7 +59,9 @@ constant and nonnegative. * Next this expression W is wrapped in a type - struct verify_type__ { unsigned int verify_error_if_negative_size__: W; }. + struct _gl_verify_type { + unsigned int _gl_verify_error_if_negative: W; + }. If W is negative, this yields a compile-time error. No compiler can deal with a bit-field of negative size. @@ -78,7 +75,7 @@ void function (int n) { verify (n < 0); } - * For the verify macro, the struct verify_type__ will need to + * For the verify macro, the struct _gl_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, @@ -116,11 +113,11 @@ Which of the following alternatives can be used? extern int dummy [sizeof (struct {...})]; - extern int dummy [sizeof (struct verify_type__ {...})]; + extern int dummy [sizeof (struct _gl_verify_type {...})]; extern void dummy (int [sizeof (struct {...})]); - extern void dummy (int [sizeof (struct verify_type__ {...})]); + extern void dummy (int [sizeof (struct _gl_verify_type {...})]); extern int (*dummy (void)) [sizeof (struct {...})]; - extern int (*dummy (void)) [sizeof (struct verify_type__ {...})]; + extern int (*dummy (void)) [sizeof (struct _gl_verify_type {...})]; In the second and sixth case, the struct type is exported to the outer scope; two such declarations therefore collide. GCC warns @@ -159,44 +156,75 @@ possible. */ # define _GL_GENSYM(prefix) _GL_CONCAT (prefix, _GL_COUNTER) -/* Verify requirement R at compile-time, as an integer constant expression. - Return 1. */ +/* 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))) # 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>)) -# 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__; \ - })) + struct _gl_verify_type { + unsigned int _gl_verify_error_if_negative: w; + }; +# 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 verify_true(R) \ - (!!sizeof \ - (struct { unsigned int verify_error_if_negative_size__: (R) ? 1 : -1; })) +# 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 ';'. */ + trailing ';'. If R is false, fail at compile-time, preferably + with a diagnostic that includes the string-literal DIAGNOSTIC. + + Unfortunately, unlike C1X, 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 -# if HAVE__STATIC_ASSERT -# define verify(R) _Static_assert (R, "verify (" #R ")") -# elif HAVE_STATIC_ASSERT -# define verify(R) static_assert (R, "verify (" #R ")") +/* _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 /* Draft C1X requires this #define. */ +# endif # else -# define verify(R) \ - extern int (* _GL_GENSYM (verify_function) (void)) [verify_true (R)] + +/* 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. */ + +# define verify_true(R) _GL_VERIFY_TRUE (R, "verify_true (" #R ")") + +/* Verify requirement R at compile-time, as a declaration without a + trailing ';'. */ + +# define verify(R) _GL_VERIFY (R, "verify (" #R ")") + # endif #endif |