Re: new platform & S_IFGITLINK problem

From: Linus Torvalds <torvalds@linux-foundation.org>
Date: May 4, 2010, 03:39 UTC
Message-ID: <alpine.LFD.2.00.1005032035310.5478@i5.linux-foundation.org>
In-Reply-To: <7vfx2b2ft5.fsf@alter.siamese.dyndns.org>

On Sat, 1 May 2010, Junio C Hamano wrote:

> 
> Yikes.  The current codebase pretty much assumes that IFREG is 0100000,
> IFDIR 0040000, and IFLNK 0120000, and the bits read from "struct stat" and
> the mode bits we store in the index and tree objects are interchangeable.

Yeah. This is painful. I knew it was wrong to just assume everything was sane and used the same traditional values, but I optimistically thought that the st_mode bits were the _one_ thing that everybody agrees on.

I was wrong.

> Yes, that assumption is a gross POSIX violation but we so far haven't seen
> any platform that matters in real life that assigns the IFMT bits
> differently.

Indeed. Just out of interest - Alan, what _is_ the crazy platform that doesn't match what absolutely everybody else has always done?

> We would need to:
> 
>  (1) rename S_IFGITLINK to GIT_S_IFMODULE;

I'd suggest dropping the "_S_" part, and just calling it

	GIT_IFxyz
	GIT_ISxyz()

Show 13 quoted lines

>  (2) define GIT_S_IF{REG,DIR,LNK} as 0100000, 0040000, and 0120000;
> 
>  (3) write MODE_SYSTEM_TO_GIT() macro to convert from S_IF{REG,DIR,LNK} we
>      read from struct stat to the "canonical" GIT_S_IF{REG,DIR,LNK}
>      values; and
> 
>  (4) change all the code that read mode from struct stat and use it to
>      first use MODE_SYSTEM_TO_GIT().
> 
> Currently 'git grep -e "S_IF[A-Z]" -e "struct stat"' reports around 250
> hits, so it is not infeasible amount of work, but it is not a trivial and
> mechanical replacement, either.  I or somebody need to set aside a block
> of time to do this clean-up and audit the result.

Ugh. And since nobody sane has different values from the system ones, if we miss some case we'll never notice on any sane platform ;(

		Linus