Why is the identifier "printf" known by the frontend?

[BCS]

Walter Bright wrote:
> Wolfgang Draxinger wrote:
>> What is the reason for that? "import std.stdio" is not a real
>> difficult thing to type.
> 
> Because I find it verrryy handy in writing minimal test cases. writefln, 
> in order to work, requires much of D and Phobos to be working properly. 
> printf, being part of the C library, doesn't require any of Phobos and 
> very little of D to work, so it's handy when things are broken.

Could this be put under a compiler switch?

-dbg	compiler debug mode