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

From: Jim Meyering <jim@meyering.net>
Date: Jun 25, 2007, 22:08 UTC
Message-ID: <87odj3sn5q.fsf@rho.meyering.net>
In-Reply-To: <alpine.LFD.0.98.0706251450240.8675@woody.linux-foundation.org>

Linus Torvalds <torvalds@linux-foundation.org> wrote:

Show 21 quoted lines

> On Mon, 25 Jun 2007, Jim Meyering wrote:
>>
>> Here's a version of that patch that retains the fflush call
>> and adds a comment explaining why it's needed.
>
> Ok. I will hereby just suggest to Junio that he just not take patches from
> you.
>
> You seem to be totally unable to ever really think or worry about your own
> little uninteresting test-case, and have shown yourself totally
> uninterested in anything anybody ever tells you.
>
> In other words, you now screwed up EPIPE.
>
> AGAIN.
>
> And why? All apparently because you want "disk full" rather than just
> "write error".
>
> Jim, you really need to see past your small test, and think about the
> bigger picture.

No. I don't keep the "small", git-specific, picture in mind all the time. Git is the only project I contribute to with this no-EPIPE restriction, and it doesn't come naturally yet.

Here's the patch you seem to want.

--------------------------------------------------------- Without this patch, git-rev-list unnecessarily omits strerror(errno) from its diagnostic, upon write failure:

    $ ./git-rev-list --max-count=1 HEAD > /dev/full
    fatal: write failure on standard output

With the patch, git reports the desired ENOSPC diagnostic:

    fatal: write failure on standard output: No space left on device

* builtin-rev-list (show_commit): Diagnose a failed fflush call.

Signed-off-by: Jim Meyering <jim@meyering.net>
---
 builtin-rev-list.c |    7 ++++++-
 1 files changed, 6 insertions(+), 1 deletions(-)

diff --git a/builtin-rev-list.c b/builtin-rev-list.c
index 813aadf..94f8fca 100644
--- a/builtin-rev-list.c
+++ b/builtin-rev-list.c
@@ -100,7 +100,12 @@ static void show_commit(struct commit *commit)
 		printf("%s%c", buf, hdr_termination);
 		free(buf);
 	}
-	fflush(stdout);
+
+	/* Flush regularly.
+	   This is especially important for an asynchronous consumer.  */
+	if (fflush(stdout) && errno != EPIPE)
+		die("write failure on standard output: %s", strerror(errno));
+
 	if (commit->parents) {
 		free_commit_list(commit->parents);
 		commit->parents = NULL;