I included the compiler version in the first post, but here it is again. I have expanded upon the bug and provided the actual output of the code. Looking at the implementation of is_virtual_base_of<>, it appears that it makes some assumptions regarding the sizeof() a class with and without virtual inheritance that are perhaps invalid? i686-apple-darwin10-g++-4.2.1 (GCC) 4.2.1 (Apple Inc. build 5646) (dot 1) #include <stdio.h> #include <boost/type_traits/is_virtual_base_of.hpp> struct A { int x; }; struct B { int y; }; struct C : public A, public B { int z; }; struct D : public A, virtual public B { int z; }; struct E : public A, public B { virtual void test(){}; int z; }; int main( int argc, char** argv ) { printf( "A,C %d\n", (int)boost::is_virtual_base_of<A,C>::value ); printf( "B,C %d\n", (int)boost::is_virtual_base_of<B,C>::value ); printf( "A,D %d\n", (int)boost::is_virtual_base_of<A,D>::value ); printf( "virtual B,D %d\n", (int)boost::is_virtual_base_of<B,D>::value ); printf( "A,E %d\n", (int)boost::is_virtual_base_of<A,E>::value ); printf( "B,E %d\n", (int)boost::is_virtual_base_of<B,E>::value ); printf( "sizeof(A) %ld\n", sizeof(A) ); printf( "sizeof(B) %ld\n", sizeof(B) ); printf( "sizeof(C) %ld\n", sizeof(C) ); printf( "sizeof(D) %ld\n", sizeof(D) ); printf( "sizeof(E) %ld\n", sizeof(E) ); return 0; } ================ A,C 0 B,C 0 A,D 1 virtual B,D 1 A,E 1 B,E 1 sizeof(A) 4 sizeof(B) 4 sizeof(C) 12 sizeof(D) 24 sizeof(E) 24 On Feb 11, 2010, at 12:59 PM, John Maddock wrote:
cast the bool to an int, still does not work. It works for most cases, for example this works:
struct C : public A, public B { virtual test(); // }
struct C : public A, public B { virtual test(); float parameter; // DOESN"T WORK ANY MORE };
Which specific compiler version? I need something that I can reproduce here... John.
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