Note that adding a syntax check before each check will certainly make "configure" somewhat slower.  Should we prefer increasing security at the cost of something slower?

original submission:

> So the CMake project is considering adding a preliminary syntax check
> (with a verbose error message) in addition to the full check (which
> fails rather silently), so that such disabling does not go unnoticed:

Feel free to correct me if I am missing something, but I don't see how that is possible.

How would you check for certain compiler extensions which may cause syntax errors if unsupported?

Something like GCC case ranges:

int
main (void)
{
  switch (2)
    {
    case 0 ... 5:
      return 0;
    default:
      return 1;
    }
}

Would cause a syntax error on other compilers. I don't see a way of differentiating that from a case like that CMake script.