On Fri, 2011-08-26 at 16:40 -0400, Nick Bowler wrote:

quoted

Extra marks will be awarded for
working out how to make unconverted code generate a compile warning ;)

It's possible to (ab)use the C preprocessor to accomplish this sort of
thing.  For instance, consider the following:

  #include <stdio.h>

  int foo(int x)
  {
     return x;
  }

  /* Deprecated; call foo instead. */
  static inline int __attribute__((deprecated)) foo_unconverted(int x, int unused)
  {
     return foo(x);
  }

  #define PASTE(a, b) a ## b
  #define PASTE2(a, b) PASTE(a, b)
  
  #define NARG_(_9, _8, _7, _6, _5, _4, _3, _2, _1, n, ...) n
  #define NARG(...) NARG_(__VA_ARGS__, 9, 8, 7, 6, 5, 4, 3, 2, 1, :)

  #define foo1(...) foo(__VA_ARGS__)
  #define foo2(...) foo_unconverted(__VA_ARGS__)
  #define foo(...) PASTE2(foo, NARG(__VA_ARGS__)(__VA_ARGS__))

Very neat ;-)