Linux Standard Base Specification 1.2
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Version Definitions

Symbol definitions are contained in the special section .gnu.version_d which has a section type of SHT_GNU_verdef. The number of entries in this section is contained in the DT_VERDEFNUM entry of the Dynamic Section. The sh_link member of the section header points to the section that contains the strings referenced by this section.

Figure 6-1. Version Definition Entries

typedef struct {
	Elfxx_Half    vd_version;
	Elfxx_Half    vd_flags;
	Elfxx_Half    vd_ndx;
	Elfxx_Half    vd_cnt;
	Elfxx_Word    vd_hash;
	Elfxx_Word    vd_aux;
	Elfxx_Word    vd_next;
} Elfxx_Verdef;

vd_version: Version revision. This value is currently set to 1, and will be reset if the versioning implementation is incompatibly altered.
vd_flags: Version information flag bitmask.
vd_ndx: Version index numeric value referencing the SHT_GNU_versym section.
vd_cnt: Number of associated verdaux array entries.
vd_hash: Version name hash value (ELF hash function).
vd_aux: Offset to a corresponding entry in the verdaux array, in bytes.
vd_next: Offset to the next verdef entry, in bytes.

Figure 6-2. Version Definition Auxiliary Entries

typedef struct {
	Elfxx_Word    vda_name;
	Elfxx_Word    vda_next;
} Elfxx_Verdaux;

vda_name: Offset to the version or dependency name string in the section header, in bytes.
vda_next: Offset to the next verdaux entry, in bytes.