Re: git bugs

[Junio C Hamano <gitster@pobox.com>]

Jeff King <peff@peff.net> writes:

> On Tue, Jun 10, 2008 at 10:44:43AM -0700, Linus Torvalds wrote:
>
>> You can fix this multiple ways. One would be to pick another size that is 
>> simply less likely (eg ~0 instead), which leaves the theoretical race, and 
>> just makes it practically impossible to hit (not that I think it's very 
>> practical to hit already).
>
> Hmm. I may have just hit it in the test suite.
>
> Try this:
>
>   cd git/t
>   for i in `seq 1 1000`; do
>     ./t4126-apply-empty.sh -v -i || break
>   done
>   echo made it to $i
>
> Most of the time it works, but somewhere in that thousand (generally
> within a few hundred), I end up with a failed test.
> ...
> However, I can still trigger the failure with your patch, so I wonder if
> it is some other race entirely...

This is not a race but the test itself is simply buggy.

When telling apply to affect index and work tree at the same time (that is
what --index means), the caller must make sure that the diff-files won't
report stale stat information.

If "git reset --hard" and ">empty" crossed the second boundary, the reset
might have written out an empty "empty" with timestamp T and then the
independent ">empty" would have given a new timestamp T+1.

I think "reset --hard" without ">empty" is enough as the head commit
records an empty blob there.

---

 t/t4126-apply-empty.sh |    4 ----
 1 files changed, 0 insertions(+), 4 deletions(-)

diff --git a/t/t4126-apply-empty.sh b/t/t4126-apply-empty.sh
index 0cfd47c..ceb6a79 100755
--- a/t/t4126-apply-empty.sh
+++ b/t/t4126-apply-empty.sh
@@ -26,7 +26,6 @@ test_expect_success setup '
 
 test_expect_success 'apply empty' '
 	git reset --hard &&
-	>empty &&
 	rm -f missing &&
 	git apply patch0 &&
 	test_cmp expect empty
@@ -34,7 +33,6 @@ test_expect_success 'apply empty' '
 
 test_expect_success 'apply --index empty' '
 	git reset --hard &&
-	>empty &&
 	rm -f missing &&
 	git apply --index patch0 &&
 	test_cmp expect empty &&
@@ -43,7 +41,6 @@ test_expect_success 'apply --index empty' '
 
 test_expect_success 'apply create' '
 	git reset --hard &&
-	>empty &&
 	rm -f missing &&
 	git apply patch1 &&
 	test_cmp expect missing
@@ -51,7 +48,6 @@ test_expect_success 'apply create' '
 
 test_expect_success 'apply --index create' '
 	git reset --hard &&
-	>empty &&
 	rm -f missing &&
 	git apply --index patch1 &&
 	test_cmp expect missing &&