[cfe-dev] [libc++] Comparing vector<T*>::iterator to vector<T*>::const_iterator&

Ryuta Suzuki ryuuta at gmail.com
Fri Jul 22 22:29:32 PDT 2011


The following program cannot be compiled 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
  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.


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
./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)

Please note that there's no error produced when libstdc++ used.
My expectation was that libc++ silently convert iterator to const_iterator
if necessary, but I guess I'm wrong.

Any comments will be greatly appreciated.


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