Eric Lemings wrote:
Ohhh...now I remember. That's the case that is not currently covered by
the standard. The standard only specifies the following ctor:
tuple (const tuple&);
It does not require this ctor:
tuple (tuple&);
And because of the stricter type checking I mentioned earlier, a
`tuple<int>' value will not bind to a `const tuple<int>&' ctor (which I
really found surprising).
That would be a bug. One of const T& or T&& has to be a match
for all invocations of a copy ctor (for homogeneous types).
See the following thread from GNU libstdc++ for more info:
http://gcc.gnu.org/ml/libstdc++/2008-02/msg00047.html
Should we add the ctor even if the standard does not (currently) specify
it?
I don't think it's needed or desirable. In the test case I
posted, we want to call the const T& overload.
Martin
Brad.
-----Original Message-----
From: Martin Sebor [mailto:[EMAIL PROTECTED] On Behalf Of Martin Sebor
Sent: Wednesday, July 02, 2008 12:32 PM
To: [email protected]
Subject: error on tuple copy ctor
As a heads up, while playing with the brand spanking new tuple
I ran into the error below. Looks like some of the ambiguities
we talked about are still there.
$ cat z.cpp \
&& make CPPOPTS=-D_RWSTD_EXT_CXX_0X CXXOPTS=-std=gnu++0x z
#include <tuple>
int main () {
std::tuple<int> t;
std::tuple<int> u (t);
}
gcc -c -I/home/sebor/stdcxx-4.3.x/include/ansi -D_RWSTDDEBUG
-pthread
-I/home/sebor/stdcxx-4.3.x/include
-I/build/sebor/stdcxx-4.3.x-gcc-4.3.0-15D/include
-I/home/sebor/stdcxx-4.3.x/examples/include -D_RWSTD_EXT_CXX_0X
-pedantic -nostdinc++ -g -W -Wall -Wcast-qual -Winline -Wshadow
-Wwrite-strings -Wno-long-long -Wcast-align -std=gnu++0x z.cpp
/home/sebor/stdcxx-4.3.x/include/rw/_tuple.h: In constructor
'__rw::__rw_tuple<_HeadT, _TailT ...>::__rw_tuple(_HeadU&&, _TailU&&
...) [with _HeadU = std::tuple<int>&, _TailU = , _HeadT =
int, _TailT = ]':
/home/sebor/stdcxx-4.3.x/include/tuple:110: instantiated from
'std::tuple<_Types>::tuple(_TypesU&& ...) [with _TypesU =
std::tuple<int>&, _TypesT = int]'
z.cpp:5: instantiated from here
/home/sebor/stdcxx-4.3.x/include/rw/_tuple.h:115: error:
cannot convert
'std::tuple<int>' to 'int' in initialization
make: *** [z.o] Error 1
