In http://reviews.llvm.org/D9157#159383, @rsmith wrote:
> What is the motivation for this? Every version of libstdc++ I can find uses
> the keyword `bool` and not a typedef.
Sorry for the late reply Richard... I've also lost the previous thread I had
with. I originally suggested the motivation was for cases like,
typedef bool BOOL;
class Foo {
static const BOOL __is_signed;
};
#include <map>
int main() {}
But as you pointed out, this is ill-formed. I found a smaller example, which
I'm confident is well-formed yet rejected by Clang,
typedef bool Bool;
#define bool Bool
#include <algorithm>
int main(void) {}
I see the following errors
In file included from blentest.c:4:
In file included from
/usr/lib/gcc/x86_64-linux-gnu/4.9/../../../../include/c++/4.9/algorithm:61:
In file included from
/usr/lib/gcc/x86_64-linux-gnu/4.9/../../../../include/c++/4.9/bits/stl_algobase.h:63:
/usr/lib/gcc/x86_64-linux-gnu/4.9/../../../../include/c++/4.9/ext/numeric_traits.h:63:25:
error: expected member name or ';' after declaration specifiers
static const bool __is_signed = __glibcxx_signed(_Value);
~~~~~~~~~~~~~~~~~ ^
/usr/lib/gcc/x86_64-linux-gnu/4.9/../../../../include/c++/4.9/ext/numeric_traits.h:74:50:
error: expected unqualified-id
const bool __numeric_traits_integer<_Value>::__is_signed;
^
/usr/lib/gcc/x86_64-linux-gnu/4.9/../../../../include/c++/4.9/ext/numeric_traits.h:106:25:
error: expected member name or ';' after declaration specifiers
static const bool __is_signed = true;
~~~~~~~~~~~~~~~~~ ^
/usr/lib/gcc/x86_64-linux-gnu/4.9/../../../../include/c++/4.9/ext/numeric_traits.h:115:51:
error: expected unqualified-id
const bool __numeric_traits_floating<_Value>::__is_signed;
^
In file included from blentest.c:4:
In file included from
/usr/lib/gcc/x86_64-linux-gnu/4.9/../../../../include/c++/4.9/algorithm:61:
/usr/lib/gcc/x86_64-linux-gnu/4.9/../../../../include/c++/4.9/bits/stl_algobase.h:941:49:
error: expected unqualified-id
&& !__gnu_cxx::__numeric_traits<_ValueType1>::__is_signed
^
/usr/lib/gcc/x86_64-linux-gnu/4.9/../../../../include/c++/4.9/bits/stl_algobase.h:946:45:
error: non-type template argument of type 'Bool' (aka 'bool') is not an
integral constant expression
return std::__lexicographical_compare<__simple>::__lc(__first1, __last1,
^~~~~~~~
6 errors generated.
The only restrictions I can see stated in the C++ standard (N4296, 2014-11-19)
are in section 17.6.4.3.1, and they only cover that you're not allowed to
`#define` or `#undef` names declared in a standard library header, or
`override`, `final` and some other bits about attributes. `bool` is a
fundamental type, so I think my example above should be accepted.
I think reopening PR9804 for this was incorrect, it looks quite similar, but
perhaps I should open a new PR for this issue. Do you agree?
Thank you for your time. :)
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