Re: RFC: case insensitive for #include

[Chris Lattner <clattner at apple dot com>]

On Jan 28, 2009, at 12:24 PM, H.J. Lu wrote:

> On Wed, Jan 28, 2009 at 12:21 PM, Chris Lattner <clattner@apple.com>  
> wrote:
> > On Jan 28, 2009, at 11:51 AM, H.J. Lu wrote:
> >
> > > Hi,
> > >
> > > I got a request to try "FOO.H" if foo.h doesn't exist when dealing
> > > with
> > >
> > > #include "foo.h"
> > >
> > > Any comments?
> >
> > I strongly recommend against this, unless this is only a "last  
> > chance" fall
> > back.
> >
> > From a performance standpoint, if you have -Idir1 -Idir2 -Idir3,  
> > you don't
> > want to stat all variants of "foo.h" in dir1 before moving on to  
> > dir2.  If
> > you do a full search for foo.h in all appropriate search paths, and  
> > then
> > redo it only on failure, then the performance issue goes away.   
> > However, in
> > that  case you get very difficult to explain behavior if you have  
> > multiple
> > files with spelling variants of foo.h in different search paths.
>
> I won't stat all variants of "foo.h". I think scandir will work here  
> and
> this feature will be supported only if scandir is available.

HJ, this is a very performance sensitive part of the preprocessor.   
Just doing a scandir would be a huge cost.

-Chris