The following program:
typedef __builtin_va_list __gnuc_va_list;
typedef __gnuc_va_list va_list;

typedef int __attribute__ ((mode(TI))) PascalLongestInt;

void f (int global_flags, ...)
{
  va_list p;
  __builtin_va_start(p,global_flags);
  {
    long long int num = __builtin_va_arg(p,PascalLongestInt);
  }
  __builtin_va_end(p);
}

couses a segfault in `cc1' for native x86_64 compiler. I have tried
3.3, 3.4.0 and 3.5.0 20040516 (experimental) with the same result.