Re: Is this a bug in comeau?

Bart van Ingen Schenau <>
Sun, 5 Oct 2008 15:24:46 CST
Faisal Vali wrote:

comeau online appears to compile this without ambiguity:

struct S { };

I will assume you meant
  struct R { };

struct S : R { };

int f(S) { return 0; }

struct T {
   operator S() { return S(); }
   operator R() { return R(); }

T t;
int x = f(t); // This call should be ambiguous

I don't see any reason for that call to be ambiguous.
There is only one way to transform a T object into an S object, and that
is through T::operator S().
T::operator R() can not be involved, because there is no conversion from
an R to an S.

If the function had been
  int f(R) { return 0; }
then the call would still not have been ambiguous.
In this case, both T::operator R() and T::operator S() could be used for
the conversion, but T::operator S() is disregarded as it requires an
additional conversion from derived class to base class that is not
needed for T::operaor R(). Therefor, T::operator R() is preferred.

This is a bug, right?
Faisal Vali
Radiation Oncology

Bart v Ingen Schenau

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