Subject: Re: [PATCH 1/2] prefer xwrite instead of write

From: Junio C Hamano <[email-masked]>
Date: Fri, 17 Jan 2014 11:07:34 -0800

Jonathan Nieder <[email-masked]> writes:

> Hi,
>
> Erik Faye-Lund wrote:
>
>> --- a/builtin/merge.c
>> +++ b/builtin/merge.c
>> @@ -367,7 +367,7 @@ static void squash_message(struct commit *commit, struct commit_list *remotehead
>>  			sha1_to_hex(commit->object.sha1));
>>  		pretty_print_commit(&ctx, commit, &out);
>>  	}
>> -	if (write(fd, out.buf, out.len) < 0)
>> +	if (xwrite(fd, out.buf, out.len) < 0)
>>  		die_errno(_("Writing SQUASH_MSG"));
>
> Shouldn't this use write_in_full() to avoid a silently truncated result? (*)

Meaning this?  If so, I think it makes sense.

 builtin/merge.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/builtin/merge.c b/builtin/merge.c
index 6e108d2..a6a38ee 100644
--- a/builtin/merge.c
+++ b/builtin/merge.c
@@ -367,7 +367,7 @@ static void squash_message(struct commit *commit, struct commit_list *remotehead
 			sha1_to_hex(commit->object.sha1));
 		pretty_print_commit(&ctx, commit, &out);
 	}
-	if (xwrite(fd, out.buf, out.len) < 0)
+	if (write_in_full(fd, out.buf, out.len) != out.len)
 		die_errno(_("Writing SQUASH_MSG"));
 	if (close(fd))
 		die_errno(_("Finishing SQUASH_MSG"));

>
> [...]
>> --- a/streaming.c
>> +++ b/streaming.c
>> @@ -538,7 +538,7 @@ int stream_blob_to_fd(int fd, unsigned const char *sha1, struct stream_filter *f
>>  			goto close_and_exit;
>>  	}
>>  	if (kept && (lseek(fd, kept - 1, SEEK_CUR) == (off_t) -1 ||
>> -		     write(fd, "", 1) != 1))
>> +		     xwrite(fd, "", 1) != 1))
>
> Yeah, if we get EINTR then it's worth retrying.
>
> [...]
>> --- a/transport-helper.c
>> +++ b/transport-helper.c
>> @@ -1129,9 +1129,8 @@ static int udt_do_write(struct unidirectional_transfer *t)
>>  		return 0;	/* Nothing to write. */
>>  
>>  	transfer_debug("%s is writable", t->dest_name);
>> -	bytes = write(t->dest, t->buf, t->bufuse);
>> -	if (bytes < 0 && errno != EWOULDBLOCK && errno != EAGAIN &&
>> -		errno != EINTR) {
>> +	bytes = xwrite(t->dest, t->buf, t->bufuse);
>> +	if (bytes < 0 && errno != EWOULDBLOCK) {
>
> Here the write is limited by BUFFERSIZE, and returning to the outer
> loop to try another read when the write returns EAGAIN, like the
> original code does, seems philosophically like the right thing to do.
>
> Luckily we don't use O_NONBLOCK anywhere, so the change shouldn't
> matter in practice.  So although it doesn't do any good, using xwrite
> here for consistency should be fine.
>
> So my only worry is the (*) above.  With that change,
> Reviewed-by: Jonathan Nieder <[email-masked]>
>
> -- 

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