• Jeff King's avatar
    move setting of object->type to alloc_* functions · fe24d396
    Jeff King authored
    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: default avatarJeff King <[email protected]>
    Signed-off-by: default avatarJunio C Hamano <[email protected]>
    fe24d396
tag.c 3.92 KB