http://gcc.gnu.org/bugzilla/show_bug.cgi?id=49044
Summary: [C++0x] mangling overload in decltype
Product: gcc
Version: 4.6.1
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
AssignedTo: unassig...@gcc.gnu.org
ReportedBy: len...@yahoo.com.cn
Created attachment 24283
--> http://gcc.gnu.org/bugzilla/attachment.cgi?id=24283
preprocessed file of tmpl_decl2.cpp
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(((T*)0)->get(i))
{
return p->get(i);
}
#endif
};
class A;
typedef W<A> B;
class A{
protected:
int _i;
public:
A():_i(0)
{}
int get(int i)const
{
return _i-i;
}
int get()const
{
return _i;
}
};
int main()
{
int s;
B b;
s=b.test1(0);
s+=b.test2(0);
#ifdef TESTCASE3
s+=b.test3(0);
#endif
return s;
}
==========================================================================
This bug is closely realted to the bug 49042. In this bug, TESTCASE3 is the
same as the TESTCASE4 in bug 49042.
While g++ 4.6 can handle TESTCASE4 in bug 49042, it can not handle in this bug,
just because there is two get() in class A.
In fact, test2() also involves overloaded A::get() and g++ 4.6 can handle it
successfully. However, test3() uses A::get() in decltype and g++ 4.6 rejects it
with an error message "sorry, unimplemented: mangling overload".
I have checked other "mangling overload" reports in this bugzilla, and I don't
find any other cases which gives similar situation.
btw, g++ 4.4, 4.5 both reject test3() with other error messages, so
this is not a regression error.
output of "g++ -v -save-temps -std=c++0x -c tmpl_decl2.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_decl2.cpp -mtune=generic -march=x86-64 -std=c++0x
-fpch-preprocess -fstack-protector -o tmpl_decl2.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_decl2.ii -quiet -dumpbase tmpl_decl2.cpp -mtune=generic -march=x86-64
-auxbase tmpl_decl2 -std=c++0x -version -fstack-protector -o tmpl_decl2.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_decl2.cpp: In instantiation of ‘decltype ((T*)(0)->.get(i))
W<T>::test3(Ta&&) [with Ta = int, T = A, decltype ((T*)(0)->.get(i)) = int]’:
tmpl_decl2.cpp:67:14: instantiated from here
tmpl_decl2.cpp:29:28: sorry, unimplemented: mangling overload
==========================================================================
