c++/9126: g++ incorrectly prefers non-template user-defined conversion operator

[martin at xemacs dot org]

>Number:         9126
>Category:       c++
>Synopsis:       g++ incorrectly prefers non-template user-defined conversion operator
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    unassigned
>State:          open
>Class:          wrong-code
>Submitter-Id:   net
>Arrival-Date:   Thu Jan 02 02:16:02 PST 2003
>Closed-Date:
>Last-Modified:
>Originator:     Martin Buchholz
>Release:        gcc-3.2
>Organization:
>Environment:
Linux x86
>Description:
When a function has both an "ordinary" user-defined
conversion operator and a templated one, the
ordinary one should be preferred, but only if
there is no other reason to prefer the templated one.

In the example below, the conversion operator template
specialized for "long" is an exact match for the call to f.

So the argument for f should be provided by
the instantiation of the template with "long".

With g++, the program exits with return code 1.
With icc (and likely Comeau C++), the program exits
with return code 0.

-----------------------------------------

struct C
{
  inline operator int () { return 1; }
  template <class T> inline operator T () { return 0; }
};

inline long f (long x) { return x; }

int
main (int argc, char *argv[])
{
  return f (C ());
}
>How-To-Repeat:
Put code into "file.cc" and then:
g++ file.cc && ./a.out; echo $?   ==> exit status 1
icc file.cc && ./a.out; echo $?   ==> exit status 0
>Fix:

>Release-Note:
>Audit-Trail:
>Unformatted: