diff options
Diffstat (limited to 'lib/verify.h')
-rw-r--r-- | lib/verify.h | 61 |
1 files changed, 50 insertions, 11 deletions
diff --git a/lib/verify.h b/lib/verify.h index a40d58a63..9fa5111b6 100644 --- a/lib/verify.h +++ b/lib/verify.h @@ -20,6 +20,26 @@ #ifndef VERIFY_H # define VERIFY_H 1 +/* Define 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). + 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'. */ +# if (4 < __GNUC__ || (__GNUC__ == 4 && 6 <= __GNUC_MINOR__)) && !defined __cplusplus +# define 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 +# 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. @@ -31,7 +51,12 @@ Symbols ending in "__" are private to this header. - The code below uses several ideas. + If _Static_assert works, verify (R) uses it directly. Similarly, + verify_true (R) 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 + compilers that do not support _Static_assert: * The first step is ((R) ? 1 : -1). Given an expression R, of integral or boolean or floating-point type, this yields an @@ -109,15 +134,9 @@ __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 + * 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. * In C++, any struct definition inside sizeof is invalid. Use a template type to work around the problem. */ @@ -148,6 +167,20 @@ 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__; \ + })) # else # define verify_true(R) \ (!!sizeof \ @@ -157,7 +190,13 @@ template <int w> /* Verify requirement R at compile-time, as a declaration without a trailing ';'. */ -# define verify(R) \ +# if HAVE__STATIC_ASSERT +# define verify(R) _Static_assert (R, "verify (" #R ")") +# elif HAVE_STATIC_ASSERT +# define verify(R) static_assert (R, "verify (" #R ")") +# else +# define verify(R) \ extern int (* _GL_GENSYM (verify_function) (void)) [verify_true (R)] +# endif #endif |