RFC: case insensitive for #include

[Chris Lattner]

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