Re: Overload resolution of function templates

From:
Rolf Magnus <ramagnus@t-online.de>
Newsgroups:
comp.lang.c++
Date:
Fri, 03 Oct 2008 17:35:16 +0200
Message-ID:
<gc5e3k$hbo$00$1@news.t-online.com>
mojumbo wrote:

On Oct 3, 10:07 am, matthias.neuba...@gmail.com wrote:

I have problems understanding how overloading of function templates
works.

Consider first the following code without any function templates ...

  int foo(const char *& c)
  {
    return 0;
  }

  int foo(const char *c)
  {
    return 1;
  }

  int main() {
    const char * s = "Hi!";
    return foo(s);
  }

  template<typename C>
  int foo_t(C& c)
  {
   return 0;
  }

  template<typename C>
  int foo_t(const C *c)
  {
   return 1;
  }

  int main() {
    const char * s = "Hi!";
    return foo_t(s);
  }

some implementations I tested (g++, msvc) seem to find a best
candidate function for foo_i which I do not understand.

As I read 13.3.1 para 7 of the standard, I would expect an
implementation to first determine specializations for foo_t (here:
foo_t<const char *> and foo_t<char> resp.), and then proceed as above.
Hence, I'd also expect an ambiguity error here. Where is my
misunderstanding?


The specializations are determined but now your function arguments
have changed. The two methods become:

int foot_t(const char*&)
and
int foo_t(const char**)


Why? foo_t(const char**) wouldn't fit, and it wouldn't even be a possible
template instance (what would the template argument C be?).
But foo_t(const char*) would fit (with C=char). And actually, my compiler is
choosing that one.

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