Re: ambiguous constructor? Is it right?

Barry <>
Tue, 25 Sep 2007 19:36:29 +0800
Zeppe wrote:

Dear all,

I have the following problem, that I'll try to explain with a very
minimal example:

class A

class B
    B() { }
    B(const A&) { }
    B(const B&) { }

class C
    operator A() const { return A(); }
    operator B() const { return B(); }

int main(){
    const C& c = C();
    B b = static_cast<B>(c);
    return 0;

Basically, I would expect that casting a const C& to B would call the
operator B() of C and that the construction C -> B (through the copy

what makes "operator B()" have higher priority?

constructor) would be preferred to C -> A -> B. In Visual C++ 9 it
actually does so, but gcc complains that there is an ambiguity. Who's
right (I guess Visual c++) and, in case, how could I nicely work around
the problem?

gcc is right,
You can compile using VC with /Za option, which disables the extension,
and produces the compile error.
I know ya gonna complain. :-)


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