Re: Cannot convert int (aka NULL) to std::vector<double*>::value_type

[Nick <nospam at codesniffer dot com>]

On Mon, 2013-02-04 at 20:08 -0800, mmcwilli@uvic.ca wrote:
> Hello All
> 
> I have a compilation error in a very large program. We have managed to
> isolate the problem with the following test problem:
> 
> #include <vector>
> #include <iostream>
> 
> using namespace std;
> 
> int main()
> {
> double* myPointer=NULL; // no error on this line
> vector<double*> myVect(1,NULL); // error on this line
> return 0;
> }
> 
> Compiling this spits out the error:
> 
> Cannot convert 'int' to 'std::vector<double*>::value_type {aka double*}'
> 
> When I compile this on GNU gcc compiler version 4.5.1 I do not get this
> error. When I compile it on GNU gcc compiler version 4.7.1 I get the
> error.
> 
> Note that this error occurs on a colleagues computer that I do not have
> access to so I cannot give the exact source code and the exact error and
> all the other details.
> 
> Since the first reference to NULL works then we can conclude that NULL is
> defined and it can be used to initialize pointers. However when NULL is
> passed as an initialization to a std::vector container it is no longer
> type compatible.
> 
> Is this a bug in the 4.7.1 compiler or did the compiler change to conform
> to some standard that does not allow vector's to initialized to NULL.
> 
> I just want to check with you all before I submit it as a bug. Any
> comments would be much appreciated!
> 
> Thanks
> Mike
> 
Confirmed w/ GCC 4.7.2:


nick@nimble ~/temp6 $ cat ./test.cpp 
#include <vector>
#include <iostream>

using namespace std;

int main()
{
	vector<double*> myVect(1,NULL);
}
nick@nimble ~/temp6 $ g++-4.7.2  -std=c++11 ./test.cpp 
In file included from /usr/lib/gcc/i686-pc-linux-gnu/4.7.2/include/g
++-v4/vector:65:0,
                 from ./test.cpp:1:
/usr/lib/gcc/i686-pc-linux-gnu/4.7.2/include/g++-v4/bits/stl_vector.h:
In instantiation of 'void std::vector<_Tp,
_Alloc>::_M_initialize_dispatch(_Integer, _Integer, std::__true_type)
[with _Integer = int; _Tp = double*; _Alloc = std::allocator<double*>]':
/usr/lib/gcc/i686-pc-linux-gnu/4.7.2/include/g
++-v4/bits/stl_vector.h:393:4:   required from 'std::vector<_Tp,
_Alloc>::vector(_InputIterator, _InputIterator, const allocator_type&)
[with _InputIterator = int; _Tp = double*; _Alloc =
std::allocator<double*>; std::vector<_Tp, _Alloc>::allocator_type =
std::allocator<double*>]'
./test.cpp:8:31:   required from here
/usr/lib/gcc/i686-pc-linux-gnu/4.7.2/include/g
++-v4/bits/stl_vector.h:1137:4: error: invalid conversion from 'int' to
'std::vector<double*>::value_type {aka double*}' [-fpermissive]
/usr/lib/gcc/i686-pc-linux-gnu/4.7.2/include/g
++-v4/bits/stl_vector.h:1179:7: error:   initializing argument 2 of
'void std::vector<_Tp, _Alloc>::_M_fill_initialize(std::vector<_Tp,
_Alloc>::size_type, const value_type&) [with _Tp = double*; _Alloc =
std::allocator<double*>; std::vector<_Tp, _Alloc>::size_type = unsigned
int; std::vector<_Tp, _Alloc>::value_type = double*]' [-fpermissive]



But I see that if you use a variable or 'nullptr' it works:

nick@nimble ~/temp6 $ cat ./test.cpp 
#include <vector>
#include <iostream>

using namespace std;

int main()
{
	double* myPointer=NULL;
	vector<double*> myVect(1,myPointer);
}
nick@nimble ~/temp6 $ g++-4.7.2  -std=c++11 ./test.cpp 
nick@nimble ~/temp6 $ 



nick@nimble ~/temp6 $ cat ./test.cpp 
#include <vector>
#include <iostream>

using namespace std;

int main()
{
	vector<double*> myVect(1,nullptr);
}
nick@nimble ~/temp6 $ g++-4.7.2  -std=c++11 ./test.cpp 
nick@nimble ~/temp6 $ 


Nick