Re: [PATCH] git-rev-list: give better diagnostic for failed write

On Mon, 25 Jun 2007, Jim Meyering wrote:

And this is a perfect example of what's wrong with the whole thing.

Dammit, how many times do I need to say this:

 - If you want reliable errors, don't use stdio!

That fflush is there FOR A REASON. You removed it FOR A MUCH LESS IMPORTANT REASON!

That fflush is there exactly because WE DO NOT WANT TO BUFFER the list of commits, because that thing is meant very much to be used for pipelines, and it's quite common that the receiving end is going to do something asynchronous with the result, and can - and does - want the results as soon as possible.

IOW, things like "gitk" use git-rev-list exactly to get the list of commits, and they want that list *incrementally*. They don't want to wait for git-rev-list to have filled up some 8kB buffer of commits. Especially since generating those commits can be slow if we're talking about a big tree and some path-limited stuff.

So for example, do something like

	git rev-list HEAD -- drivers/char/drm/Makefile

and if you don't see the result scroll a line at a time on a slower machine, there's something *wrong*.

Junio, I'm NAK'ing this very forcefully!

Jim: I don't know what I'm doing wrong, but I'm apparently not reaching 
you. So let me try one more time:

 - stdio really isn't very good with error handling

 - if you use stdio, YOU HAD BETTER ACCEPT THAT

 - don't screw up basic functionality in your *insane* quest to get stdio 
   to give you ENOSPC. It's not going to happen. Not that way. Just face 
   the fact that stdio *will* throw error numbers away.

The whole notion of "buffered IO" and "reliable errors" is simply not something that goes well together.

			Linus