Part1

#define FOO(x) do { foo(x); bar(x); } while (0)
if (condition)
    FOO(x);
else
    ....

Part 2

do {
  // do something
  if (error) {
    break;
  }
  // do something else
  if (error) {
    break;
  }
  // etc..
} while (0);

Utilisation d'une ellipse en macro C.

Exemple :
#define dbgprintf(...) realdbgprintf (FILE, LINE, __VA_ARGS)
dbgprintf ("Hello, world");
which expands to:
realdbgprintf (FILE, LINE__, "Hello, world");