Created attachment 24282 [details]
the preprocessed file of tmpl_decl.cpp

preprocessed file is in the attachment.

the source code is shown as below:
==========================================================================
template<typename T> class W{
protected:
	T* p;

public:
	W()
	{
		p=new T();
	}

	~W()
	{
		if(p)
			delete p;
	}

	auto test1(int i) -> decltype(p->get(i))
	{
		return p->get(i);
	}

	template<typename Ta>int test2(Ta&& i)
	{
		return p->get(i);
	}
	
#if 1// bug in g++ 4.4, 4.5 & 4.6
#define TESTCASE3
	template<typename Ta>auto test3(Ta&& i) -> decltype(p->get(i))
	{
		return p->get(i);
	}
#endif

#if 1 // bug in g++ 4.4 & 4.5
#define TESTCASE4
	// this is an ugly workground for 4.6
	template<typename Ta>auto test4(Ta&& i) -> decltype(((T*)0)->get(i))
	{
		return p->get(i);
	}
#endif
};

class A;

typedef W<A> B;

class A{
protected:
	int _i;
public:
	A():_i(0)
	{}

	A(int i):_i(i)
	{}

	int get(int i)const
	{
		return _i-i;
	}

};

int main()
{
	int s;
	B b;
	s+=b.test1(0);
	s+=b.test2(0);
	
#ifdef TESTCASE3
	s+=b.test3(0);
#endif
	
#ifdef TESTCASE4
	s+=b.test4(0);
#endif
	return s;
}
==========================================================================
While test1(), test2() are all ok for g++ -std=c++0x from 4.4 to 4.6,
test3() is rejected by all, and test4() is accepted only by 4.6.

G++4.6 gives a strange error message for test3() such as "tmpl_decl.cpp:3:5: error: ‘A* W<A>::p’ is protected", while it accepts "p" in test1().

btw, g++ 4.4, 4.5 both reject test3() and test4() with other error messages, so this is not a regression error.

output of "g++ -v -save-temps -std=c++0x -c tmpl_decl.cpp"
==========================================================================
Using built-in specs.
COLLECT_GCC=g++
COLLECT_LTO_WRAPPER=/usr/lib/x86_64-linux-gnu/gcc/x86_64-linux-gnu/4.6.1/lto-wrapper
Target: x86_64-linux-gnu
Configured with: ../src/configure -v --with-pkgversion='Ubuntu 4.6.0-3~ppa1' --with-bugurl=file:///usr/share/doc/gcc-4.6/README.Bugs --enable-languages=c,c++,fortran,objc,obj-c++,go --prefix=/usr --program-suffix=-4.6 --enable-shared --enable-multiarch --with-multiarch-defaults=x86_64-linux-gnu --enable-linker-build-id --with-system-zlib --libexecdir=/usr/lib/x86_64-linux-gnu --without-included-gettext --enable-threads=posix --with-gxx-include-dir=/usr/include/c++/4.6 --libdir=/usr/lib/x86_64-linux-gnu --enable-nls --with-sysroot=/ --enable-clocale=gnu --enable-libstdcxx-debug --enable-libstdcxx-time=yes --enable-plugin --enable-objc-gc --disable-werror --with-arch-32=i686 --with-tune=generic --enable-checking=release --build=x86_64-linux-gnu --host=x86_64-linux-gnu --target=x86_64-linux-gnu
Thread model: posix
gcc version 4.6.1 20110409 (prerelease) (Ubuntu 4.6.0-3~ppa1) 
COLLECT_GCC_OPTIONS='-v' '-save-temps' '-std=c++0x' '-c' '-shared-libgcc' '-mtune=generic' '-march=x86-64'
 /usr/lib/x86_64-linux-gnu/gcc/x86_64-linux-gnu/4.6.1/cc1plus -E -quiet -v -D_GNU_SOURCE tmpl_decl.cpp -mtune=generic -march=x86-64 -std=c++0x -fpch-preprocess -fstack-protector -o tmpl_decl.ii
ignoring nonexistent directory "/usr/local/include/x86_64-linux-gnu"
ignoring nonexistent directory "/usr/lib/x86_64-linux-gnu/gcc/x86_64-linux-gnu/4.6.1/../../../../../x86_64-linux-gnu/include"
#include "..." search starts here:
#include <...> search starts here:
 /usr/include/c++/4.6
 /usr/include/c++/4.6/x86_64-linux-gnu
 /usr/include/c++/4.6/backward
 /usr/lib/x86_64-linux-gnu/gcc/x86_64-linux-gnu/4.6.1/include
 /usr/local/include
 /usr/lib/x86_64-linux-gnu/gcc/x86_64-linux-gnu/4.6.1/include-fixed
 /usr/include/x86_64-linux-gnu
 /usr/include
End of search list.
COLLECT_GCC_OPTIONS='-v' '-save-temps' '-std=c++0x' '-c' '-shared-libgcc' '-mtune=generic' '-march=x86-64'
 /usr/lib/x86_64-linux-gnu/gcc/x86_64-linux-gnu/4.6.1/cc1plus -fpreprocessed tmpl_decl.ii -quiet -dumpbase tmpl_decl.cpp -mtune=generic -march=x86-64 -auxbase tmpl_decl -std=c++0x -version -fstack-protector -o tmpl_decl.s
GNU C++ (Ubuntu 4.6.0-3~ppa1) version 4.6.1 20110409 (prerelease) (x86_64-linux-gnu)
        compiled by GNU C version 4.6.1 20110409 (prerelease), GMP version 4.3.2, MPFR version 3.0.0-p8, MPC version 0.9
GGC heuristics: --param ggc-min-expand=63 --param ggc-min-heapsize=62982
GNU C++ (Ubuntu 4.6.0-3~ppa1) version 4.6.1 20110409 (prerelease) (x86_64-linux-gnu)
        compiled by GNU C version 4.6.1 20110409 (prerelease), GMP version 4.3.2, MPFR version 3.0.0-p8, MPC version 0.9
GGC heuristics: --param ggc-min-expand=63 --param ggc-min-heapsize=62982
Compiler executable checksum: 9b2d061a0b3f0ab5a4eef825b71a3b00
tmpl_decl.cpp: In function ‘int main()’:
tmpl_decl.cpp:3:5: error: ‘A* W<A>::p’ is protected
tmpl_decl.cpp:74:14: error: within this context
==========================================================================