Jeff King <peff@xxxxxxxx> writes:
> On Thu, Dec 31, 2015 at 12:10:33PM +0700, Duy Nguyen wrote:
>
>> On Tue, Dec 29, 2015 at 1:35 PM, Jeff King <peff@xxxxxxxx> wrote:
>> > We sometimes use 32-bit unsigned integers as bit-fields.
>> > It's fine to access the MSB, because it's unsigned. However,
>> > doing so as "1 << 31" is wrong, because the constant "1" is
>> > a signed int, and we shift into the sign bit, causing
>> > undefined behavior.
>> >
>> > We can fix this by using "1U" as the constant.
>>
>> We have this in cache.h, should it be fixed as well?
>>
>> /* CE_EXTENDED2 is for future extension */
>> #define CE_EXTENDED2 (1 << 31)
>
> Sort of. We don't actually use it, and since it's a macro, that means it
> never even hits the compiler proper itself. So it's not a bug, but it's
> a bug waiting to happen. :)
>
> -Peff
Let's squash an obvious change for that in to 1/2, then, before I
merge the series to 'next'.
Thanks.
-- >8 --
From: Jeff King <peff@xxxxxxxx>
Date: Tue, 29 Dec 2015 01:35:46 -0500
Subject: [PATCH] avoid shifting signed integers 31 bits
We sometimes use 32-bit unsigned integers as bit-fields.
It's fine to access the MSB, because it's unsigned. However,
doing so as "1 << 31" is wrong, because the constant "1" is
a signed int, and we shift into the sign bit, causing
undefined behavior.
We can fix this by using "1U" as the constant.
Signed-off-by: Jeff King <peff@xxxxxxxx>
Signed-off-by: Junio C Hamano <gitster@xxxxxxxxx>
---
builtin/receive-pack.c | 2 +-
cache.h | 2 +-
diff.h | 2 +-
3 files changed, 3 insertions(+), 3 deletions(-)
diff --git a/builtin/receive-pack.c b/builtin/receive-pack.c
index e6b93d0..e35ed40 100644
--- a/builtin/receive-pack.c
+++ b/builtin/receive-pack.c
@@ -1597,7 +1597,7 @@ static void prepare_shallow_update(struct command *commands,
continue;
si->need_reachability_test[i]++;
for (k = 0; k < 32; k++)
- if (si->used_shallow[i][j] & (1 << k))
+ if (si->used_shallow[i][j] & (1U << k))
si->shallow_ref[j * 32 + k]++;
}
diff --git a/cache.h b/cache.h
index 6f53962..9088843 100644
--- a/cache.h
+++ b/cache.h
@@ -214,7 +214,7 @@ struct cache_entry {
#define CE_INTENT_TO_ADD (1 << 29)
#define CE_SKIP_WORKTREE (1 << 30)
/* CE_EXTENDED2 is for future extension */
-#define CE_EXTENDED2 (1 << 31)
+#define CE_EXTENDED2 (1U << 31)
#define CE_EXTENDED_FLAGS (CE_INTENT_TO_ADD | CE_SKIP_WORKTREE)
diff --git a/diff.h b/diff.h
index f7208ad..893f446 100644
--- a/diff.h
+++ b/diff.h
@@ -91,7 +91,7 @@ typedef struct strbuf *(*diff_prefix_fn_t)(struct diff_options *opt, void *data)
#define DIFF_OPT_DIRSTAT_BY_LINE (1 << 28)
#define DIFF_OPT_FUNCCONTEXT (1 << 29)
#define DIFF_OPT_PICKAXE_IGNORE_CASE (1 << 30)
-#define DIFF_OPT_DEFAULT_FOLLOW_RENAMES (1 << 31)
+#define DIFF_OPT_DEFAULT_FOLLOW_RENAMES (1U << 31)
#define DIFF_OPT_TST(opts, flag) ((opts)->flags & DIFF_OPT_##flag)
#define DIFF_OPT_TOUCHED(opts, flag) ((opts)->touched_flags & DIFF_OPT_##flag)
--
2.7.0-rc3-132-g73ad441
--
To unsubscribe from this list: send the line "unsubscribe git" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html