[PATCH] cache: flush stdio before restoring FDs

[John Keeping]

As described in commit 2efb59e (ui-patch: Flush stdout after outputting
data, 2014-06-11), we need to ensure that stdout is flushed before
restoring the file descriptor when writing to the cache.  It turns out
that it's not just ui-patch that is affected by this but also raw diff
which writes to stdout internally.

Let's avoid risking more places doing this by ensuring that stdout is
flushed after writing in fill_slot().

Signed-off-by: John Keeping <john at keeping.me.uk>
---
On Mon, Apr 24, 2017 at 11:54:40AM -0400, Konstantin Ryabitsev wrote:
> Very reminiscent of a fix for ui-patch.c that fixed patch truncation [1]
> there's a similar problem with cached rawdiff output. E.g.:
> 
> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/rawdiff/?id=v4.11-rc7&id2=v4.11-rc8
> 
> You will notice that the output is truncated (if it isn't just reload to 
> get the cached version).
> 
> I would love a speedy fix, as we're trying to use this in place of 
> publishing pre-generated patches.

I guess it's the same problem we fixed before for ui-patch, so here's a
patch to move the fix into the common path for all pages.

 cache.c    | 6 ++++++
 ui-patch.c | 2 --
 2 files changed, 6 insertions(+), 2 deletions(-)

diff --git a/cache.c b/cache.c
index 6736a01..2ccdc4e 100644
--- a/cache.c
+++ b/cache.c
@@ -224,6 +224,12 @@ static int fill_slot(struct cache_slot *slot)
 	/* Generate cache content */
 	slot->fn();
 
+	/* Make sure any buffered data is flushed to the file */
+	if (fflush(stdout)) {
+		close(tmp);
+		return errno;
+	}
+
 	/* update stat info */
 	if (fstat(slot->lock_fd, &slot->cache_st)) {
 		close(tmp);
diff --git a/ui-patch.c b/ui-patch.c
index 047e2f9..6745b69 100644
--- a/ui-patch.c
+++ b/ui-patch.c
@@ -92,6 +92,4 @@ void cgit_print_patch(const char *new_rev, const char *old_rev,
 		log_tree_commit(&rev, commit);
 		printf("-- \ncgit %s\n\n", cgit_version);
 	}
-
-	fflush(stdout);
 }
-- 
2.12.2.648.g6730d8bc62.dirty