Problem with PFE approach [Was: Faster compilation speed]

[Jeff Epler]

On Mon, Aug 19, 2002 at 11:50:24AM -0700, Devang Patel wrote:
>  
> On Monday, August 19, 2002, at 06:26  AM, jepler@unpythonic.net wrote: 
> 
> 
> > The following set of files will compile a program with or without 
> > PFE, but 
> > using a PFE that contains both a.h and b.h, the behavior will 
> > change. 
> > 
>  
> 
> This is not implementation problem or PFE model problem. 
> If you are including a.h and b.h in PFE means what you're asking 
> compiler to do  
> is to compile following source 
> 
> 
> /// m.c 
> #include "a.h" 
> #include "b.h" 
> int main(void) { 
> #ifdef DEFB 
> 	return 1; 
> #else 
> 	return 0; 
> #endif; 
> } 

.. then the build system must treat m.c as depending on the PFE, which
in turn depends on all headers it contains.  But that's where this
discussion started, with the PFE cure being worse than the illness since
it makes your whole project recompile when you touch a header file.

Jeff