[cfe-dev] ccache and 'unused argument' warning

[Chris Lattner]

On Jun 19, 2010, at 10:47 AM, bruce.r.stephens at gmail.com wrote:
> Chris Lattner <clattner-2kanFRK1NckAvxtiuMwx3w at public.gmane.org> writes:
> 
> The assumption seems to be that preprocessing is relatively cheap, which
> (IIUC) isn't valid for clang, so perhaps ccache (as it exists now) just
> isn't worth using?

The tradeoffs change: clang's preprocessor is about 2x faster than GCC's, so preprocessing does remain relatively cheap in the cases where it is also cheap for gcc.  However, if your .c file includes a ton of headers and has relatively little code, you can end up burning more time preprocessing than actually compiling.  This is independent of what compiler you use.

-Chris