Date: Wed, 10 Jul 2013 18:04:16 +0100 From: David Chisnall <theraven@FreeBSD.org> To: "O. Hartmann" <ohartman@zedat.fu-berlin.de> Cc: FreeBSD CURRENT <freebsd-current@FreeBSD.org>, freebsd-toolchain@FreeBSD.org Subject: Re: CURRENT: CLANG 3.3 and -stad=c++11 and -stdlib=libc++: isnan()/isninf() oddity Message-ID: <C8C94CF2-7D5A-471B-AD63-8E961AED6274@FreeBSD.org> In-Reply-To: <20130710183315.725dfde0@thor.walstatt.dyndns.org> References: <20130710155809.0f589c22@thor.walstatt.dyndns.org> <CD51F125-AE9E-4461-916D-CF583002B47D@FreeBSD.org> <20130710183315.725dfde0@thor.walstatt.dyndns.org>
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On 10 Jul 2013, at 17:33, "O. Hartmann" <ohartman@zedat.fu-berlin.de> =
wrote:
> Hi David,
>=20
> thanks for the fast response.
>=20
> The code I was told to check with is this:
>=20
> #include <iostream>
> #include <typeinfo>
> #include <cmath>
>=20
> int
> main(void)
> {
>=20
> std::cout << typeid(isnan(1.0)).name() << "\n";
>=20
> }
>=20
>=20
> If I compile it with=20
>=20
> c++ -o testme -std=3Dc++11 -stdlib=3Dlibc++ source.cc
>=20
> and run the binary, the result is "i" which I interpret as "INT".
I believe there is a bug, which is that the math.h things are being =
exposed but shouldn't be, however it is not the bug that you think it =
is. Try this line instead:
std::cout << typeid(std::isnan(1.0)).name() << "\n";
We have a libm function, isnan(), and a libc++ function, std::isnan(). =
The former is detected if you do not specify a namespace. I am not sure =
what will happen if you do:
#include <iostream>
#include <typeinfo>
#include <cmath>
using namespace std;
int
main(void)
{
cout << typeid(isnan(1.0)).name() << "\n";
}
This is considered bad form, but does happen in some code. I am not =
certain what the precedence rules are in this case and so I don't know =
what happens.
To properly fix this, we'd need to namespace the libm functions when =
including math.h in C++. This would also include fixing tweaking the =
macros. =20
A fix for your code is to ensure isnan() and isinf() are explicitly =
namespaced. Potentially, this may also work:
using std::isinf;
using std::isnan;
David
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