is_convertible_basic_impl causes compile error when used inside OpenMP loop

[therealremi@…]

In the following example compile error is generated under Visual 2008, if "default(none)" is used for OpenMP variable data sharing attribute clauses (which is the recommended choice). It's practically a deal breaker when a novice user tries to use boost with OpenMP. And I would say OpenMP use will only grow.

#define BOOST_ALL_NO_LIB 1

#include <boost/graph/adjacency_list.hpp>

#include <omp.h>

int main(int argc, char* argv[]) {

typedef boost::adjacency_list<boost::vecS, boost::vecS, boost::undirectedS> GraphType;

typedef GraphType::adjacency_iterator GraphAdjacencyIterator;

const unsigned int vertex_count( 20 );

typedef std::pair<int, int> EdgeType;

std::vector<EdgeType> edges;

const GraphType graph( edges.begin(), edges.end(), vertex_count, edges.size() );

int i( 0 );

#pragma omp parallel for schedule(static, 1) default(none) private(i) shared(vertex_count, graph)

for ( i = 0; i < vertex_count; ++i ) {

const std::pair<GraphAdjacencyIterator, GraphAdjacencyIterator> adjacent (

boost::adjacent_vertices(i, graph)

);

}

return 0;

}

"\boost\boost/type_traits/is_convertible.hpp(263) : error C3052: '_m_from' : variable doesn't appear in a data-sharing clause under a default(none) clause"

[therealremi@…]

Sory for bad formating. Again:

#define BOOST_ALL_NO_LIB 1
#include <boost/graph/adjacency_list.hpp>
#include <omp.h>


int main(int argc, char* argv[])
{
	typedef boost::adjacency_list<boost::vecS, boost::vecS, boost::undirectedS> GraphType;
	typedef GraphType::adjacency_iterator GraphAdjacencyIterator;
	const unsigned int vertex_count( 20 );
	typedef std::pair<int, int> EdgeType;
	std::vector<EdgeType> edges;
	const GraphType graph( edges.begin(), edges.end(), vertex_count, edges.size() );

	int i( 0 );
	#pragma omp parallel for schedule(static, 1) default(none) private(i) shared(vertex_count, graph)
	for ( i = 0; i < vertex_count; ++i )
	{
		const std::pair<GraphAdjacencyIterator, GraphAdjacencyIterator> adjacent
		(
			boost::adjacent_vertices(i, graph)
		);
	}

    return 0;
} 

[John Maddock]

Here's the thing - I don't see that there is anything we can do at out end to fix this as private/shared attribute can only be added in the OMP declaration?

For example adding

boost::detail::is_convertible_basic_impl<boost::detail::iterator_category_with_traversal<std::input_iterator_tag,boost::random_access_traversal_tag> &, std::input_iterator_tag>::_m_from

to the shared list in your OMP declaration fixes the compile.

Of course that then makes your code depend on an implementation detail, which it clearly shouldn't do :-(

To be honest I don't understand why MSVC is complaining here, given that it's producing an error for something that clearly is not used as a variable in the loop, GCC compiles your code just fine BTW with g++ -omp.

Closing for now since I can't see how we can fix, please reopen if there is a fix we can apply at our end.