> -----Original Message----- > From: Travis Vitek [mailto:[EMAIL PROTECTED] > Sent: Thursday, June 12, 2008 4:00 PM > To: dev@stdcxx.apache.org > Subject: RE: static_assert config check > > > > Martin Sebor wrote: > >Travis Vitek wrote: > >>> Eric Lemings wrote: > >>> > >>> > >>> How's this for a suitable configuration check for static_assert? > >>> > >>> // compile-only test > >>> > >>> static_assert (sizeof (char) == 1, "impossible"); > >>> > >>> template <int I> struct S { > >>> static_assert (I >= 0, "template parameter I must be > >>> non-negative"); > >>> }; > >>> > >> > >> I've written an errily similar test already (pasted below) > >> > >> I think you should probably instantiate S somewhere and it > might be a > >> good idea put a line break before 'struct' so that your code > >> conforms to our 'coding standards'. > >[...] > > > >It's probably overkill, but just as an FYI, to verify this works > >both ways the test would need to be negative, i.e., named NO_XXX, > >and write #define _RWSTD_NO_XXX to stdout if the negative assert > >failed to fire. > > So how exactly is the test supposed to write anything to stdout if it > doesn't compile? If the expression of the static_assert is false, the > program is ill-formed and the compiler is to emit a diagnostic. > > I'm looking at this and if I name the test NO_STATIC_ASSERT.cpp and it > fails to compile, the macro _RWSTD_NO_STATIC_ASSERT wll be defined, so > using the NO_ prefix doesn't really buy me anything. I don't think it > would be right to make it so that if a NO_XXX test fails to > compile the > macro _RWSTD_NO_XXX will not be defined. > > The only way I see to ensure that static_assert is actually > working both > ways is to write two tests, one testing for passing conditions > [STATIC_ASSERT_PASS.cpp], and the other testing for failing conditions > [STATIC_ASSERT_FAIL.cpp]. Then we would define _RWSTD_NO_STATIC_ASSERT > like so... > > #if !defined (_RWSTD_NO_STATIC_ASSERT_PASS) > || defined (_RWSTD_NO_STATIC_ASSERT_FAIL) > // STATIC_ASSERT_PASS.cpp failed to compile > // STATIC_ASSERT_FAIL.cpp compiled without error > # define _RWSTD_NO_STATIC_ASSERT > #endif > > Is that overkill?
Or...you could run the negative test _first_ and if that fails (i.e. does not fire as assertion), run the positive test which will produce _RWSTD_NO_STATIC_ASSERT only if one or both tests failed. Brad.
