This patch introduces the MSB() macro to obtain the desired number of
most significant bits from a given variable independently of the variable
type.
It is then used to better implement the overflow test on the OBJ_OFS_DELTA
base offset variable with the property of always working correctly
regardless of the type/size of that variable.
Signed-off-by: Nicolas Pitre <nico@xxxxxxx>
---
builtin-pack-objects.c | 2 +-
builtin-unpack-objects.c | 2 +-
git-compat-util.h | 8 ++++++++
index-pack.c | 2 +-
sha1_file.c | 2 +-
5 files changed, 12 insertions(+), 4 deletions(-)
diff --git a/builtin-pack-objects.c b/builtin-pack-objects.c
index 6bff17b..ee607a0 100644
--- a/builtin-pack-objects.c
+++ b/builtin-pack-objects.c
@@ -1014,7 +1014,7 @@ static void check_object(struct object_entry *entry)
ofs = c & 127;
while (c & 128) {
ofs += 1;
- if (!ofs || ofs & ~(~0UL >> 7))
+ if (!ofs || MSB(ofs, 7))
die("delta base offset overflow in pack for %s",
sha1_to_hex(entry->sha1));
c = buf[used_0++];
diff --git a/builtin-unpack-objects.c b/builtin-unpack-objects.c
index 3956c56..63f7db6 100644
--- a/builtin-unpack-objects.c
+++ b/builtin-unpack-objects.c
@@ -209,7 +209,7 @@ static void unpack_delta_entry(enum object_type type, unsigned long delta_size,
base_offset = c & 127;
while (c & 128) {
base_offset += 1;
- if (!base_offset || base_offset & ~(~0UL >> 7))
+ if (!base_offset || MSB(base_offset, 7))
die("offset value overflow for delta base object");
pack = fill(1);
c = *pack;
diff --git a/git-compat-util.h b/git-compat-util.h
index 139fc19..bcfcb35 100644
--- a/git-compat-util.h
+++ b/git-compat-util.h
@@ -13,6 +13,14 @@
#define ARRAY_SIZE(x) (sizeof(x)/sizeof(x[0]))
+#ifdef __GNUC__
+#define TYPEOF(x) (__typeof__(x))
+#else
+#define TYPEOF(x)
+#endif
+
+#define MSB(x, bits) ((x) & TYPEOF(x)(~0ULL << (sizeof(x) * 8 - (bits))))
+
#if !defined(__APPLE__) && !defined(__FreeBSD__)
#define _XOPEN_SOURCE 600 /* glibc2 and AIX 5.3L need 500, OpenBSD needs 600 for S_ISLNK() */
#define _XOPEN_SOURCE_EXTENDED 1 /* AIX 5.3L needs this */
diff --git a/index-pack.c b/index-pack.c
index 3c768fb..0e54aa6 100644
--- a/index-pack.c
+++ b/index-pack.c
@@ -249,7 +249,7 @@ static void *unpack_raw_entry(struct object_entry *obj, union delta_base *delta_
base_offset = c & 127;
while (c & 128) {
base_offset += 1;
- if (!base_offset || base_offset & ~(~0UL >> 7))
+ if (!base_offset || MSB(base_offset, 7))
bad_object(obj->offset, "offset value overflow for delta base object");
p = fill(1);
c = *p;
diff --git a/sha1_file.c b/sha1_file.c
index d9ca69a..ebdd497 100644
--- a/sha1_file.c
+++ b/sha1_file.c
@@ -1150,7 +1150,7 @@ static off_t get_delta_base(struct packed_git *p,
base_offset = c & 127;
while (c & 128) {
base_offset += 1;
- if (!base_offset || base_offset & ~(~0UL >> 7))
+ if (!base_offset || MSB(base_offset, 7))
die("offset value overflow for delta base object");
c = base_info[used++];
base_offset = (base_offset << 7) + (c & 127);
--
1.5.1.696.g6d352-dirty
-
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