From: SZEDER Gábor <szeder.dev@xxxxxxxxx>
We had to fix a buggy progress line recently, where the progress
counter counted backwards, see 8e118e8490 (pack-objects: update
"nr_seen" progress based on pack-reused count, 2021-04-11).
Let's add a BUG(...) assertion that makes use of the "last_update"
value to make sure this doesn't happen again, i.e. trigger a BUG()
when the counter passed to display_progress() is smaller than the
previous value.
Note that we allow subsequent display_progress() calls with the same
counter value, because:
- Strictly speaking, it's not wrong to do so.
- Forbidding it might make the code calling display_progress() more
complex; I suspect that would be the case with e.g. the "Updating
index flags" progress line in 'unpack-trees.c', where the counter
is increased in recursive function calls.
- We would need to special case the internal display() call in
stop_progress_msg(), because it uses the same counter value as the
last display_progress() call, which would trigger this BUG().
't0500-progress-display.sh' countains a few tests that check how
shortened progress lines are covered up, and one of them ('progress
shortens - crazy caller') shortens the progress line by counting
backwards. From now on that test would trigger this BUG(), so remove
it; the other test cases cover shortening progress lines sufficiently.
Signed-off-by: SZEDER Gábor <szeder.dev@xxxxxxxxx>
Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@xxxxxxxxx>
---
WARNING: I belive this is subtly buggy, see the discussion in the
cover letter. It needs more fixes of the progress.c API usage in
various places before being ready.
progress.c | 2 ++
t/t0500-progress-display.sh | 36 ++++++++++++------------------------
2 files changed, 14 insertions(+), 24 deletions(-)
diff --git a/progress.c b/progress.c
index 40043bf6601..7b59006c7c4 100644
--- a/progress.c
+++ b/progress.c
@@ -40,6 +40,8 @@ static void display(struct progress *progress, uint64_t n,
const char *tp;
int show_update = 0;
+ if (progress->last_update != -1 && n < progress->last_update)
+ BUG("counting backwards with display_progress()");
progress->last_update = n;
if (progress->delay && (!progress_update || --progress->delay))
diff --git a/t/t0500-progress-display.sh b/t/t0500-progress-display.sh
index 3f00e52ce46..de59a757f86 100755
--- a/t/t0500-progress-display.sh
+++ b/t/t0500-progress-display.sh
@@ -211,30 +211,6 @@ EOF
test_cmp expect out
'
-# Progress counter goes backwards, this should not happen in practice.
-test_expect_success 'progress shortens - crazy caller' '
- cat >expect <<-\EOF &&
- Working hard: 10% (100/1000)<CR>
- Working hard: 20% (200/1000)<CR>
- Working hard: 0% (1/1000) <CR>
- Working hard: 100% (1000/1000)<CR>
- Working hard: 100% (1000/1000), done.
- EOF
-
- cat >in <<-\EOF &&
- start 1000
- progress 100
- progress 200
- progress 1
- progress 1000
- stop
- EOF
- test-tool progress <in 2>stderr &&
-
- show_cr <stderr >out &&
- test_cmp expect out
-'
-
test_expect_success 'progress display with throughput' '
cat >expect <<-\EOF &&
Working hard: 0, stalled.<CR>
@@ -451,4 +427,16 @@ test_expect_success 'BUG: display_progress() does not reach declared "total"' '
grep "BUG:.*total progress does not match" stderr
'
+test_expect_success 'BUG: display_progres() counting backwards' '
+ cat >in <<-\EOF &&
+ start 3
+ progress 1
+ progress 2
+ progress 1
+ EOF
+
+ test_must_fail test-tool progress <in 2>stderr &&
+ grep "BUG:.*counting backwards" stderr
+'
+
test_done
--
2.32.0.599.g3967b4fa4ac
