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pack-objects: clamp negative depth to 0

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A negative delta depth makes no sense, and the code is not prepared to
handle it. If passed "--depth=-1" on the command line, then this line
from break_delta_chains():

	cur->depth = (total_depth--) % (depth + 1);

triggers a divide-by-zero. This is undefined behavior according to the C
standard, but on POSIX systems results in SIGFPE killing the process.
This is certainly one way to inform the use that the command was
invalid, but it's a bit friendlier to just treat it as "don't allow any
deltas", which we already do for --depth=0.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
This commit is contained in:
Jeff King 2021-05-01 10:04:34 -04:00 committed by Junio C Hamano
parent 49ac1d33bb
commit 6d52b6a5df
2 changed files with 9 additions and 0 deletions
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2
builtin/pack-objects.c
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@ -3861,6 +3861,8 @@ int cmd_pack_objects(int argc, const char **argv, const char *prefix)
if (pack_to_stdout != !base_name || argc)
usage_with_options(pack_usage, pack_objects_options);
if (depth < 0)
depth = 0;
if (depth >= (1 << OE_DEPTH_BITS)) {
warning(_("delta chain depth %d is too deep, forcing %d"),
depth, (1 << OE_DEPTH_BITS) - 1);

7
t/t5316-pack-delta-depth.sh
View File

@ -102,4 +102,11 @@ test_expect_success '--depth=0 disables deltas' '
test_cmp expect actual
'
test_expect_success 'negative depth disables deltas' '
pack=$(git pack-objects --all --depth=-1 </dev/null pack) &&
echo 0 >expect &&
max_chain pack-$pack.pack >actual &&
test_cmp expect actual
'
test_done