Maybe a bug in G++

Maybe a bug in G++

[Sven Gohlke]

[-- Attachment #1: Type: Text/Plain, Size: 673 bytes --]

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Hello,

I think I have found an identifier lookup bug in g++ (GCC) 3.3.3 (Debian 
20040422). Attached are two files, one which compiles and one which doesn't  
though I think that it should compile.

But since I have found a workaround (or maybe a standard conforming 
solution) ...
- --
Best Regards
Sven Gohlke

GnuPG Fingerprint: 7197 61F6 AFDE F46D 914B 65C2 2A4B 5BBF 6CC0
at hkp://wwwkeys.pgp.net

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[-- Attachment #2: compiles-not.cc --]
[-- Type: text/x-c++src, Size: 1706 bytes --]

#include <iostream>

template<typename _T>
struct _TypeOf_
{
	friend class _Null_;
	private:
		template<int, typename _1>
		struct H
		{
			typedef typename _1::Type Type;
		};
		template<typename _1>
		struct H<0, _1>
		{
			typedef _1 Type;
		};

		typedef char HasType;
		typedef struct { char _[2]; }	NoType;
		template<typename _1> static NoType test (...);
		template<typename _1> static HasType test (typename _1::Type const*);
	public:
		typedef typename
			H<sizeof(test<_T>(0))==sizeof(HasType), _T>::Type Type;
};

template<typename _T1, typename _T2>
struct _IsIdentical_
{
	enum { Value = 0 };
};

template<typename _T1>
struct _IsIdentical_<_T1, _T1>
{
	enum { Value = 1 };
};

/*
 * First test type
 *
 * has an empty member type Type
*/
struct ItHas
{
	struct Type{};
};

/*
 * Second test type
 *
 * has a member type Type identical to ItHas::Type
*/
struct ItHasNot
{
	typedef ItHas::Type Type;
};

/*
 * Third test type
*/
typedef int Other;

int
main (int argc, const char **argv)
{
	/* Both test are made at compile time. No calculations are made at run
	 * time. The first calculation results to 0, the second to 1.
	*/
	std::cout << "_IsIdentical_<ItHas, ItHasNot>: " <<
		_IsIdentical_<ItHas, ItHasNot>::Value << std::endl;
	std::cout << "_IsIdentical_<ItHas, Other>: " <<
		_IsIdentical_<ItHas, Other>::Value << std::endl;
	std::cout <<
		"_IsIdentical_<_TypeOf_<ItHas>::Type, _TypeOf_<ItHasNot>::Type>: " <<
		_IsIdentical_<_TypeOf_<ItHas>::Type, _TypeOf_<ItHasNot>::Type>::Value <<
			std::endl;
	std::cout <<
		"_IsIdentical_<_TypeOf_<ItHas>::Type, _TypeOf_<Other>::Type>: " <<
		_IsIdentical_<_TypeOf_<ItHas>::Type, _TypeOf_<Other>::Type>::Value <<
			std::endl;
	return 0;
}


[-- Attachment #3: compiles.cc --]
[-- Type: text/x-c++src, Size: 1737 bytes --]

#include <iostream>

template<typename _T>
struct _TypeOf_
{
	friend class _Null_;
	private:
		template<int, typename _1>
		struct H
		{
			typedef typename _1::Type Type;
		};
		template<typename _1>
		struct H<0, _1>
		{
			typedef _1 Type;
		};

		typedef char HasType;
		typedef struct { char _[2]; }	NoType;
		template<typename _1> static NoType test (...);
		template<typename _1> static HasType test (typename _1::Type const*);
		typedef _TypeOf_ This;
	public:
		typedef typename
			H<sizeof(This::test<_T>(0))==sizeof(HasType), _T>::Type Type;
};

template<typename _T1, typename _T2>
struct _IsIdentical_
{
	enum { Value = 0 };
};

template<typename _T1>
struct _IsIdentical_<_T1, _T1>
{
	enum { Value = 1 };
};

/*
 * First test type
 *
 * has an empty member type Type
*/
struct ItHas
{
	struct Type{};
};

/*
 * Second test type
 *
 * has a member type Type identical to ItHas::Type
*/
struct ItHasNot
{
	typedef ItHas::Type Type;
};

/*
 * Third test type
*/
typedef int Other;

int
main (int argc, const char **argv)
{
	/* Both test are made at compile time. No calculations are made at run
	 * time. The first calculation results to 0, the second to 1.
	*/
	std::cout << "_IsIdentical_<ItHas, ItHasNot>: " <<
		_IsIdentical_<ItHas, ItHasNot>::Value << std::endl;
	std::cout << "_IsIdentical_<ItHas, Other>: " <<
		_IsIdentical_<ItHas, Other>::Value << std::endl;
	std::cout <<
		"_IsIdentical_<_TypeOf_<ItHas>::Type, _TypeOf_<ItHasNot>::Type>: " <<
		_IsIdentical_<_TypeOf_<ItHas>::Type, _TypeOf_<ItHasNot>::Type>::Value <<
			std::endl;
	std::cout <<
		"_IsIdentical_<_TypeOf_<ItHas>::Type, _TypeOf_<Other>::Type>: " <<
		_IsIdentical_<_TypeOf_<ItHas>::Type, _TypeOf_<Other>::Type>::Value <<
			std::endl;
	return 0;
}

Re: Maybe a bug in G++

[Andrew Pinski]

On Jul 18, 2004, at 10:30 AM, Sven Gohlke wrote:

> -----BEGIN PGP SIGNED MESSAGE-----
> Hash: SHA1
>
> Hello,
>
> I think I have found an identifier lookup bug in g++ (GCC) 3.3.3 
> (Debian
> 20040422). Attached are two files, one which compiles and one which 
> doesn't
> though I think that it should compile.

Yes this is a bug in 3.3.x and before but it has been fixed in 3.4.0 
and newer.

Thanks,
Andrew Pinski