[Bug c++/28385] New: templated function call goes awry

["Colin dot McCabe at ecitele dot com" <gcc-bugzilla at gcc dot gnu dot org>]

I have compiled the following code under gcc 3.4.6, 4.0.2, and 4.1.1:
=========================================================
#include <iostream>

class Foo {
  public:
    template<typename T>
    void operator()(const T& fcn) {
        std::cout << "calling fcn()..." << std::endl;
        fcn();
    }
};

void bar() {
    std::cout << "bar()" << std::endl;
}

int main() {
    Foo myFoo;
    myFoo(bar);
    myFoo(&bar);
    return 0;
}
========================================================
Output for gcc 4.0.2 and 4.1.1:

calling bar()...
calling bar()...
bar()

Output for gcc 3.4.6:
calling bar()...
bar()
calling bar()...
bar()

Also, if you change 
    void operator()(const T& fcn) {
to 
    void operator()(const T fcn) {
It successfully makes both function calls on every version of gcc.

Everyone knows that in C, "&function_name" and "function_name" are generally
equivalent-- you can write:
  func_ptr_type* f = &function_name;
or 
  func_ptr_type* f = function_name;

So it is surprising to me that 
  myFoo(bar);
seems to behave differently than:
  myFoo(&bar);

I'm also surprised that there is no type error or other diagnostic message in
cases where code to call bar() is omitted.


-- 
           Summary: templated function call goes awry
           Product: gcc
           Version: 4.1.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: Colin dot McCabe at ecitele dot com


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=28385