pack-objects: clamp negative depth to 0

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>

diff --git a/builtin/pack-objects.c b/builtin/pack-objects.c
index ea7a5b3ba56f08b0fd75821a87fe8a6830982246..da5e0700f9c1103a98e63ef277556ad414088663 100644 (file)
--- a/builtin/pack-objects.c
+++ b/builtin/pack-objects.c
@@ -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);

diff --git a/t/t5316-pack-delta-depth.sh b/t/t5316-pack-delta-depth.sh
index 3e84df4137ca64672ba3dd8af52a24e9409d6f5e..759169d0742c999adb33f91bc1ae1283877cb3db 100755 (executable)
--- a/t/t5316-pack-delta-depth.sh
+++ b/t/t5316-pack-delta-depth.sh
@@ -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