Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> writes:
> On Sun, 22 Apr 2007, Junio C Hamano wrote:
>>
>> This shows the single "diff --git" header line without anything,
>> to show that the path is not stat-clean, but the contents are
>> unchanged, which is what is expected.
>
> Actually, I think the "good" case is the broken one.
>
> Do an "strace -f" on the two cases, and you'll see an EBADF in the case
> that you think is good: the missing output *is* there, it's just that you
> closed the file descriptor so you don't see it.
>
> So if the output you want is with the close(1) (ie with the output
> discarded), then you have some other bug there.
I think I figured it out. The extra EBADF output comes from the
process that calls finish_command() in filter_buffer().
That is because the caller is diff_flush() which prepares its
output using stdio, and when apply_filter -> filter_bufer
callchain forks, the unflushed stdout hangs around in the
child. Then we call exit() in apply_filter() to terminate the
child we spawned to do the filtering. It flushes its copy of
stdio buffer.
Yuck.
I should be happy that I figured out what is going on, but I am
not very happy with this patch.
diff --git a/convert.c b/convert.c
index 845825b..35bb8cf 100644
--- a/convert.c
+++ b/convert.c
@@ -233,7 +233,6 @@ static int filter_buffer(const char *path, const char *src,
return 1;
}
close(pipe_feed[0]);
- close(1);
write_err = (write_in_full(pipe_feed[1], src, size) < 0);
if (close(pipe_feed[1]))
@@ -273,6 +272,7 @@ static char *apply_filter(const char *path, const char *src,
return NULL;
}
+ fflush(stdout);
child_process.pid = fork();
if (child_process.pid < 0) {
error("cannot fork to run external filter %s", cmd);
-
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