2.3.6 Slices

Slices, with kind CTF_K_SLICE, are an unusual CTF construct: they do not directly correspond to any C type, but are a way to model other types in a more convenient fashion for CTF generators.

A slice is like a pointer or other reference type in that they are always represented by ctf_stype_t: but unlike pointers and other reference types, they populate the ctt_size field just like integral types do, and come with an attached encoding and transform the encoding of the underlying type. The underlying type is described in the variable-length data, similarly to structure and union fields: see below. Requests for the type size should also chase down to the referenced type.

Slices are always nameless: ctt_name is always zero for them.

(The libctf API behaviour is unusual as well, and justifies the existence of slices: ctf_type_kind never returns CTF_K_SLICE but always the underlying type kind, so that consumers never need to know about slices: they can tell if an apparent integer is actually a slice if they need to by calling ctf_type_reference, which will uniquely return the underlying integral type rather than erroring out with ECTF_NOTREF if this is actually a slice. So slices act just like an integer with an encoding, but more closely mirror DWARF and other debugging information formats by allowing CTF file creators to represent a bitfield as a slice of an underlying integral type.)

The vlen in the info word for a slice should be ignored and is always zero. The variable-length data for a slice is a single ctf_slice_t:

typedef struct ctf_slice
{
  uint32_t cts_type;
  unsigned short cts_offset;
  unsigned short cts_bits;
} ctf_slice_t;