From d36f51c13b54a872cdaf08a1765a23afab26ae51 Mon Sep 17 00:00:00 2001 From: Jeff King Date: Sun, 13 Jul 2014 02:41:55 -0400 Subject: [PATCH] move setting of object->type to alloc_* functions The "struct object" type implements basic object polymorphism. Individual instances are allocated as concrete types (or as a union type that can store any object), and a "struct object *" can be cast into its real type after examining its "type" enum. This means it is dangerous to have a type field that does not match the allocation (e.g., setting the type field of a "struct blob" to "OBJ_COMMIT" would mean that a reader might read past the allocated memory). In most of the current code this is not a problem; the first thing we do after allocating an object is usually to set its type field by passing it to create_object. However, the virtual commits we create in merge-recursive.c do not ever get their type set. This does not seem to have caused problems in practice, though (presumably because we always pass around a "struct commit" pointer and never even look at the type). We can fix this oversight and also make it harder for future code to get it wrong by setting the type directly in the object allocation functions. This will also make it easier to fix problems with commit index allocation, as we know that any object allocated by alloc_commit_node will meet the invariant that an object with an OBJ_COMMIT type field will have a unique index number. Signed-off-by: Jeff King Signed-off-by: Junio C Hamano --- alloc.c | 5 +++++ blob.c | 2 +- builtin/blame.c | 1 - commit.c | 6 ++---- object.c | 5 ++--- object.h | 2 +- tag.c | 2 +- tree.c | 2 +- 8 files changed, 13 insertions(+), 12 deletions(-) diff --git a/alloc.c b/alloc.c index 03e458bad0..fd2e32df8c 100644 --- a/alloc.c +++ b/alloc.c @@ -52,6 +52,7 @@ static struct alloc_state blob_state; void *alloc_blob_node(void) { struct blob *b = alloc_node(&blob_state, sizeof(struct blob)); + b->object.type = OBJ_BLOB; return b; } @@ -59,6 +60,7 @@ static struct alloc_state tree_state; void *alloc_tree_node(void) { struct tree *t = alloc_node(&tree_state, sizeof(struct tree)); + t->object.type = OBJ_TREE; return t; } @@ -66,6 +68,7 @@ static struct alloc_state tag_state; void *alloc_tag_node(void) { struct tag *t = alloc_node(&tag_state, sizeof(struct tag)); + t->object.type = OBJ_TAG; return t; } @@ -73,6 +76,7 @@ static struct alloc_state object_state; void *alloc_object_node(void) { struct object *obj = alloc_node(&object_state, sizeof(union any_object)); + obj->type = OBJ_NONE; return obj; } @@ -82,6 +86,7 @@ void *alloc_commit_node(void) { static int commit_count; struct commit *c = alloc_node(&commit_state, sizeof(struct commit)); + c->object.type = OBJ_COMMIT; c->index = commit_count++; return c; } diff --git a/blob.c b/blob.c index ae320bd8fa..5720a38ca2 100644 --- a/blob.c +++ b/blob.c @@ -7,7 +7,7 @@ struct blob *lookup_blob(const unsigned char *sha1) { struct object *obj = lookup_object(sha1); if (!obj) - return create_object(sha1, OBJ_BLOB, alloc_blob_node()); + return create_object(sha1, alloc_blob_node()); if (!obj->type) obj->type = OBJ_BLOB; if (obj->type != OBJ_BLOB) { diff --git a/builtin/blame.c b/builtin/blame.c index d3b256e545..8f3e311123 100644 --- a/builtin/blame.c +++ b/builtin/blame.c @@ -2287,7 +2287,6 @@ static struct commit *fake_working_tree_commit(struct diff_options *opt, commit = alloc_commit_node(); commit->object.parsed = 1; commit->date = now; - commit->object.type = OBJ_COMMIT; parent_tail = &commit->parents; if (!resolve_ref_unsafe("HEAD", head_sha1, 1, NULL)) diff --git a/commit.c b/commit.c index 4ff8077dbf..eb24add866 100644 --- a/commit.c +++ b/commit.c @@ -61,10 +61,8 @@ struct commit *lookup_commit_or_die(const unsigned char *sha1, const char *ref_n struct commit *lookup_commit(const unsigned char *sha1) { struct object *obj = lookup_object(sha1); - if (!obj) { - struct commit *c = alloc_commit_node(); - return create_object(sha1, OBJ_COMMIT, c); - } + if (!obj) + return create_object(sha1, alloc_commit_node()); if (!obj->type) obj->type = OBJ_COMMIT; return check_commit(obj, sha1, 0); diff --git a/object.c b/object.c index 9c31e9a5e0..a950b85146 100644 --- a/object.c +++ b/object.c @@ -141,13 +141,12 @@ static void grow_object_hash(void) obj_hash_size = new_hash_size; } -void *create_object(const unsigned char *sha1, int type, void *o) +void *create_object(const unsigned char *sha1, void *o) { struct object *obj = o; obj->parsed = 0; obj->used = 0; - obj->type = type; obj->flags = 0; hashcpy(obj->sha1, sha1); @@ -163,7 +162,7 @@ struct object *lookup_unknown_object(const unsigned char *sha1) { struct object *obj = lookup_object(sha1); if (!obj) - obj = create_object(sha1, OBJ_NONE, alloc_object_node()); + obj = create_object(sha1, alloc_object_node()); return obj; } diff --git a/object.h b/object.h index 6e12f2c7f4..8020ace566 100644 --- a/object.h +++ b/object.h @@ -79,7 +79,7 @@ extern struct object *get_indexed_object(unsigned int); */ struct object *lookup_object(const unsigned char *sha1); -extern void *create_object(const unsigned char *sha1, int type, void *obj); +extern void *create_object(const unsigned char *sha1, void *obj); /* * Returns the object, having parsed it to find out what it is. diff --git a/tag.c b/tag.c index 7b07921b30..79552c716c 100644 --- a/tag.c +++ b/tag.c @@ -40,7 +40,7 @@ struct tag *lookup_tag(const unsigned char *sha1) { struct object *obj = lookup_object(sha1); if (!obj) - return create_object(sha1, OBJ_TAG, alloc_tag_node()); + return create_object(sha1, alloc_tag_node()); if (!obj->type) obj->type = OBJ_TAG; if (obj->type != OBJ_TAG) { diff --git a/tree.c b/tree.c index c8c49d7b78..ed66575079 100644 --- a/tree.c +++ b/tree.c @@ -183,7 +183,7 @@ struct tree *lookup_tree(const unsigned char *sha1) { struct object *obj = lookup_object(sha1); if (!obj) - return create_object(sha1, OBJ_TREE, alloc_tree_node()); + return create_object(sha1, alloc_tree_node()); if (!obj->type) obj->type = OBJ_TREE; if (obj->type != OBJ_TREE) {