[LLVMbugs] [Bug 10455] New: Silent conversion of vector<T*>::iterator to vector<T*>::const_iterator&

[bugzilla-daemon at llvm.org]

http://llvm.org/bugs/show_bug.cgi?id=10455

           Summary: Silent conversion of  vector<T*>::iterator to
                    vector<T*>::const_iterator&
           Product: libc++
           Version: unspecified
          Platform: PC
        OS/Version: Linux
            Status: NEW
          Severity: normal
          Priority: P
         Component: All Bugs
        AssignedTo: hhinnant at apple.com
        ReportedBy: oroppas at gmail.com
                CC: llvmbugs at cs.uiuc.edu


Hi,

The following piece of code cannot be compiled by either clang++/g++ with
libc++:

#include <vector>
#include <unordered_map>

typedef std::vector<int*> KernelVector;
typedef std::unordered_map<int*,KernelVector> KernelVectorMap;

int main()
{
  KernelVectorMap::const_iterator kernel;
  KernelVector::const_iterator subkernel = kernel->second.begin();

  std::distance( kernel->second.begin(), subkernel );

  return 0;
}

clang++ -std=c++0x -stdlib=libc++ ./const_iterator.cpp 
./const_iterator.cpp:12:3: error: no matching function for call to 'distance'
  std::distance( kernel->second.begin(), subkernel );
  ^~~~~~~~~~~~~
/usr/include/c++/v1/iterator:478:1: note: candidate template ignored: deduced
conflicting types for parameter
      '_InputIter' ('std::__1::__wrap_iter<int **>' vs.
'std::__1::__wrap_iter<int *const *>')
distance(_InputIter __first, _InputIter __last)
^
1 error generated.

or 

g++ -std=c++0x -I /usr/include/c++/v1/ ./const_iterator.cpp 
./const_iterator.cpp: In function ‘int main()’:
./const_iterator.cpp:12:52: error: no matching function for call to
‘distance(std::__1::vector<int*>::iterator,
std::__1::vector<int*>::const_iterator&)’
./const_iterator.cpp:12:52: note: candidate is:
/usr/include/c++/v1/iterator:479:47: note: template<class _InputIter> typename
std::__1::iterator_traits::difference_type std::__1::distance(_InputIter,
_InputIter)


Can iterator be silently converted to const_iterator in the case like
std::distance()?

Please take a look at the comment by David Blaikie:
http://lists.cs.uiuc.edu/pipermail/cfe-dev/2011-July/016308.html

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