[Boost-users] BGL compile error 3

6 Jun 2007


      Aaron Windsor  writes:
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On 6/5/07, gast128  wrote:
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Aaron Windsor  writes:
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On 6/4/07, gast128  wrote:
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Dear all,
We want to (DLL) export a boost graph. Probably on (DLL) exporting, the
compiler tries to generate code for every member function. However on
VC++7.1
...
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it gives then a problem with operator[]. This can be easily verified
with
...
...
the
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following case:
void Foo()
{
   boost::adjacency_list<> graph;
   graph[0];
}
We use here Boost 1.33.0. Anyone an idea?
Wkr,
me
Hi,
What are you expecting the expression "graph[0]" to do/return in the code
above?
Regards,
Aaron
Nothing. It won't compile, complaining about return type. Same error if you
try to export an adjacency_list.
Wkr,
me
graph[0] accesses the bundled properties for the first vertex in the
graph, but you've declared an empty graph with no properties. So, even
if you got it to compile by adding some properties to the graph, 0
still isn't even a valid vertex descriptor, since the graph is empty.
Regards,
Aaron
But that 's the problem I can't get it compile, even if I don't use an empty 
graph, e.g.:

void Foo()
{
    boost::adjacency_list<> graph;
    boost::adjacency_list<>::vertex_descriptor v = add_vertex(graph);
    graph[v];
}

c:\Work Sdk\Boost\boost\graph\adjacency_list.hpp(412) : error 
C2440: 'return' : cannot convert 
from 'boost::vec_adj_list_any_vertex_pa::bind_::value_type'
 to 'boost::adjacency_list<>::vertex_bundled &'
        with
        [
            Tag=boost::vertex_bundle_t,
            Graph=boost::adjacency_list<>,
            
Property=boost::detail::vertex_property_map,boost::vert
ex_bundle_t>::Property
        ]
        A reference that is not to 'const' cannot be bound to a non-lvalue
        c:\Work Sdk\Boost\boost\graph\adjacency_list.hpp(412) : while 
compiling class-template member 
function 'boost::adjacency_list<>::vertex_bundled 
&boost::adjacency_list<>::operator []
(boost::adjacency_list<>::vertex_descriptor)'
        c:\Work\Test\Testmfc\Test Boost Graph\KTestBoostGrphCompileError.cpp
(26) : see reference to class template instantiation 'boost::adjacency_list<>' 
being compiled

Wkr,
me