And here's a minor re-roll from comments on the list. I was able to reproduce and test myself this time; the patch indeed fixes the problem.
Changes from v1:
- add more standards explanation to the first commit (thanks for
pointers from Chris Torek off-list) - fixes small whitespace issues in patches 1 and 6
- new patch (5) to add "const" as appropriate
[1/6]: object-file: prefer array-of-bytes initializer for hash literals
[2/6]: object-file: drop confusing oid initializer of empty_tree struct
[3/6]: object-file: move empty_tree struct into find_cached_object()
[4/6]: object-file: drop oid field from find_cached_object() return value
[5/6]: object-file: treat cached_object values as const
[6/6]: object-file: inline empty tree and blob literals
object-file.c | 81 ++++++++++++++++++++++++---------------------------
1 file changed, 38 insertions(+), 43 deletions(-)
1: da69342eba ! 1: ec76b9eebb object-file: prefer array-of-bytes initializer for hash literals
@@ Commit message
and then use it to initialize the hash field of an object_id struct.
That hash field is exactly 32 bytes long (the size we need for sha256).
But the string literal above is actually 33 bytes long due to the NUL
- terminator. It's legal in C to initialize from a longer string literal;
- the extra bytes are just ignored.
+ terminator. This is legal in C, and the NUL is ignored.
- However, the upcoming gcc 15 will start warning about this:
+ Side note on legality: in general excess initializer elements are
+ forbidden, and gcc will warn on both of these:
+
+ char foo[3] = { 'h', 'u', 'g', 'e' };
+ char bar[3] = "VeryLongString";
+
+ I couldn't find specific language in the standard allowing
+ initialization from a string literal where _just_ the NUL is ignored,
+ but C99 section 6.7.8 (Initialization), paragraph 32 shows this exact
+ case as "example 8".
+
+ However, the upcoming gcc 15 will start warning for this case (when
+ compiled with -Wextra via DEVELOPER=1):
CC object-file.o
object-file.c:52:9: warning: initializer-string for array of ‘unsigned char’ is too long [-Wunterminated-string-initialization]
@@ object-file.c
- "\x6f\xe1\x41\xf7\x74\x91\x20\xa3\x03\x72" \
- "\x18\x13"
+#define EMPTY_TREE_SHA1_BIN_LITERAL { \
-+ 0x4b, 0x82, 0x5d, 0xc6, 0x42, 0xcb, 0x6e, 0xb9, 0xa0, 0x60, \
-+ 0xe5, 0x4b, 0xf8, 0xd6, 0x92, 0x88, 0xfb, 0xee, 0x49, 0x04 \
++ 0x4b, 0x82, 0x5d, 0xc6, 0x42, 0xcb, 0x6e, 0xb9, 0xa0, 0x60, \
++ 0xe5, 0x4b, 0xf8, 0xd6, 0x92, 0x88, 0xfb, 0xee, 0x49, 0x04 \
+}
+#define EMPTY_TREE_SHA256_BIN_LITERAL { \
-+ 0x6e, 0xf1, 0x9b, 0x41, 0x22, 0x5c, 0x53, 0x69, 0xf1, 0xc1, \
-+ 0x04, 0xd4, 0x5d, 0x8d, 0x85, 0xef, 0xa9, 0xb0, 0x57, 0xb5, \
-+ 0x3b, 0x14, 0xb4, 0xb9, 0xb9, 0x39, 0xdd, 0x74, 0xde, 0xcc, \
++ 0x6e, 0xf1, 0x9b, 0x41, 0x22, 0x5c, 0x53, 0x69, 0xf1, 0xc1, \
++ 0x04, 0xd4, 0x5d, 0x8d, 0x85, 0xef, 0xa9, 0xb0, 0x57, 0xb5, \
++ 0x3b, 0x14, 0xb4, 0xb9, 0xb9, 0x39, 0xdd, 0x74, 0xde, 0xcc, \
+ 0x53, 0x21 \
+}
+
+#define EMPTY_BLOB_SHA1_BIN_LITERAL { \
-+ 0xe6, 0x9d, 0xe2, 0x9b, 0xb2, 0xd1, 0xd6, 0x43, 0x4b, 0x8b, \
++ 0xe6, 0x9d, 0xe2, 0x9b, 0xb2, 0xd1, 0xd6, 0x43, 0x4b, 0x8b, \
+ 0x29, 0xae, 0x77, 0x5a, 0xd8, 0xc2, 0xe4, 0x8c, 0x53, 0x91 \
+}
+#define EMPTY_BLOB_SHA256_BIN_LITERAL { \
-+ 0x47, 0x3a, 0x0f, 0x4c, 0x3b, 0xe8, 0xa9, 0x36, 0x81, 0xa2, \
-+ 0x67, 0xe3, 0xb1, 0xe9, 0xa7, 0xdc, 0xda, 0x11, 0x85, 0x43, \
-+ 0x6f, 0xe1, 0x41, 0xf7, 0x74, 0x91, 0x20, 0xa3, 0x03, 0x72, \
++ 0x47, 0x3a, 0x0f, 0x4c, 0x3b, 0xe8, 0xa9, 0x36, 0x81, 0xa2, \
++ 0x67, 0xe3, 0xb1, 0xe9, 0xa7, 0xdc, 0xda, 0x11, 0x85, 0x43, \
++ 0x6f, 0xe1, 0x41, 0xf7, 0x74, 0x91, 0x20, 0xa3, 0x03, 0x72, \
+ 0x18, 0x13 \
+}
2: b8416b33d2 = 2: 0beaf2d65e object-file: drop confusing oid initializer of empty_tree struct
3: 8f5a9f5e30 = 3: d0c28cb1c9 object-file: move empty_tree struct into find_cached_object()
4: e2d0c9b56d = 4: 551e5938d5 object-file: drop oid field from find_cached_object() return value
-: ---------- > 5: d5641358a2 object-file: treat cached_object values as const
5: 7ebc8d2d2c ! 6: 82c43bfc78 object-file: inline empty tree and blob literals
@@ object-file.c
-
-#define EMPTY_TREE_SHA1_BIN_LITERAL { \
-- 0x4b, 0x82, 0x5d, 0xc6, 0x42, 0xcb, 0x6e, 0xb9, 0xa0, 0x60, \
-- 0xe5, 0x4b, 0xf8, 0xd6, 0x92, 0x88, 0xfb, 0xee, 0x49, 0x04 \
+- 0x4b, 0x82, 0x5d, 0xc6, 0x42, 0xcb, 0x6e, 0xb9, 0xa0, 0x60, \
+- 0xe5, 0x4b, 0xf8, 0xd6, 0x92, 0x88, 0xfb, 0xee, 0x49, 0x04 \
-}
-#define EMPTY_TREE_SHA256_BIN_LITERAL { \
-- 0x6e, 0xf1, 0x9b, 0x41, 0x22, 0x5c, 0x53, 0x69, 0xf1, 0xc1, \
-- 0x04, 0xd4, 0x5d, 0x8d, 0x85, 0xef, 0xa9, 0xb0, 0x57, 0xb5, \
-- 0x3b, 0x14, 0xb4, 0xb9, 0xb9, 0x39, 0xdd, 0x74, 0xde, 0xcc, \
+- 0x6e, 0xf1, 0x9b, 0x41, 0x22, 0x5c, 0x53, 0x69, 0xf1, 0xc1, \
+- 0x04, 0xd4, 0x5d, 0x8d, 0x85, 0xef, 0xa9, 0xb0, 0x57, 0xb5, \
+- 0x3b, 0x14, 0xb4, 0xb9, 0xb9, 0x39, 0xdd, 0x74, 0xde, 0xcc, \
- 0x53, 0x21 \
-}
-
-#define EMPTY_BLOB_SHA1_BIN_LITERAL { \
-- 0xe6, 0x9d, 0xe2, 0x9b, 0xb2, 0xd1, 0xd6, 0x43, 0x4b, 0x8b, \
+- 0xe6, 0x9d, 0xe2, 0x9b, 0xb2, 0xd1, 0xd6, 0x43, 0x4b, 0x8b, \
- 0x29, 0xae, 0x77, 0x5a, 0xd8, 0xc2, 0xe4, 0x8c, 0x53, 0x91 \
-}
-#define EMPTY_BLOB_SHA256_BIN_LITERAL { \
-- 0x47, 0x3a, 0x0f, 0x4c, 0x3b, 0xe8, 0xa9, 0x36, 0x81, 0xa2, \
-- 0x67, 0xe3, 0xb1, 0xe9, 0xa7, 0xdc, 0xda, 0x11, 0x85, 0x43, \
-- 0x6f, 0xe1, 0x41, 0xf7, 0x74, 0x91, 0x20, 0xa3, 0x03, 0x72, \
+- 0x47, 0x3a, 0x0f, 0x4c, 0x3b, 0xe8, 0xa9, 0x36, 0x81, 0xa2, \
+- 0x67, 0xe3, 0xb1, 0xe9, 0xa7, 0xdc, 0xda, 0x11, 0x85, 0x43, \
+- 0x6f, 0xe1, 0x41, 0xf7, 0x74, 0x91, 0x20, 0xa3, 0x03, 0x72, \
- 0x18, 0x13 \
-}
-
static const struct object_id empty_tree_oid = {
- .hash = EMPTY_TREE_SHA1_BIN_LITERAL,
-+ .hash ={
++ .hash = {
+ 0x4b, 0x82, 0x5d, 0xc6, 0x42, 0xcb, 0x6e, 0xb9, 0xa0, 0x60,
+ 0xe5, 0x4b, 0xf8, 0xd6, 0x92, 0x88, 0xfb, 0xee, 0x49, 0x04
+ },
Sam James
