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Bug 355967

Summary:	Ambiguous function call with parameter using conversion operator
Product:	[Tools] CDT	Reporter:	Marc-André Laperle <malaperle>
Component:	cdt-parser	Assignee:	Project Inbox <cdt-parser-inbox>
Status:	RESOLVED WONTFIX	QA Contact:	Markus Schorn <mschorn.eclipse>
Severity:	normal
Priority:	P3	CC:	cdtdoug
Version:	8.0
Target Milestone:	---
Hardware:	All
OS:	All
Whiteboard:

Description Marc-André Laperle

2011-08-26 13:35:22 EDT

Using CDT 8.0.0.201108031635

template <class T>
class SmartPtr
{
public:
    template<typename OtherT>
    operator const SmartPtr<OtherT>&() const
    {
        return *this;
    }

    template<typename OtherT>
    operator SmartPtr<OtherT>() const
    {
        return *this;
    }
};

class A
{
};

class B : public A
{
};

void func(SmartPtr<A>)
{

}

int main()
{
    SmartPtr<B> b;
    func(b); // func is ambiguous
}


This code compiles with MinGW GCC 4.4 but it doesn't with VC 9. I'm not sure who's right but gcc calls the operator that returns a value and that looks right to me.

Comment 1 Markus Schorn

2011-09-06 10:36:44 EDT

I thing gcc is wrong, it fails to deduce the template argument for the first conversion operator. When I replace the templates with non-template conversions then gcc reports the ambiguity:

class A {};
class B : public A {};

template <class T> class SmartPtr {
public:
    operator const SmartPtr<A>&() const;
    operator SmartPtr<A>() const;
};

void func(SmartPtr<A>) {
}

int main() {
    SmartPtr<B> b;
    func(b); // func is ambiguous
}

Comment 2 Marc-André Laperle

2011-09-06 13:21:15 EDT

Thanks!

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=50306