Re: [PATCH v3 2/5] fetch: use strbuf to format FETCH_HEAD updates
- From
Junio C Hamano <gitster@pobox.com>
- Date
- Jan 11, 2021, 23:21 UTC
- Message-ID
- <xmqqsg775abk.fsf@gitster.c.googlers.com>
- In-Reply-To
- <a19762690eb7f9957ac31d73e110f0103aeb2307.1610362744.git.ps@pks.im>
Patrick Steinhardt <ps@pks.im> writes:
Show 8 quoted lines
> @@ -909,6 +910,7 @@ static int open_fetch_head(struct fetch_head *fetch_head)
> fetch_head->fp = fopen(filename, "a");
> if (!fetch_head->fp)
> return error_errno(_("cannot open %s"), filename);
> + strbuf_init(&fetch_head->buf, 0);
> } else {
> fetch_head->fp = NULL;
> }Leaving fetch_head->buf uninitialized is probably OK as the caller of open_fetch_head() would (or at least should) immediately barf upon seeing an error return?
Ah, no. Under dry-run mode, we will return success but leave buf uninitializesd. It is safe because we do not use the strbuf when fp is NULL. OK.
Show 20 quoted lines
> @@ -941,14 +943,17 @@ static void append_fetch_head(struct fetch_head *fetch_head,
> return;
> }
>
> - fprintf(fetch_head->fp, "%s\t%s\t%s",
> - oid_to_hex_r(old_oid_hex, old_oid), merge_status_marker, note);
> + strbuf_addf(&fetch_head->buf, "%s\t%s\t%s",
> + oid_to_hex_r(old_oid_hex, old_oid), merge_status_marker, note);
> for (i = 0; i < url_len; ++i)
> if ('\n' == url[i])
> - fputs("\\n", fetch_head->fp);
> + strbuf_addstr(&fetch_head->buf, "\\n");
> else
> - fputc(url[i], fetch_head->fp);
> - fputc('\n', fetch_head->fp);
> + strbuf_addch(&fetch_head->buf, url[i]);
> + strbuf_addch(&fetch_head->buf, '\n');
> +
> + strbuf_write(&fetch_head->buf, fetch_head->fp);
> + strbuf_reset(&fetch_head->buf);This gets us closer to fixing the "one record can be written out with multiple write(2) calls, allowing parallel fetches to corrupt FETCH_HEAD file by intermixed records" problem (even though this change alone would not solve it---for that we need to do write ourselves, not letting stdio do the flushing).
Show 11 quoted lines
> } > > static void commit_fetch_head(struct fetch_head *fetch_head) > @@ -962,6 +967,7 @@ static void close_fetch_head(struct fetch_head *fetch_head) > return; > > fclose(fetch_head->fp); > + strbuf_release(&fetch_head->buf); > } > > static const char warn_show_forced_updates[] =