As described in 32–Bit Environments and 64–Bit Environments, the 64–bit link-editor, ld(1), is capable of generating 32–bit objects. In addition, the 32–bit link-editor is capable of generating 64–bit objects. Each of these objects has an associated support interface defined.
The support interface for 64–bit objects is similar to the interface of 32–bit objects, but ends in a 64 suffix. For example ld_start() and ld_start64(). This convention allows both implementations of the support interface to reside in a single shared object of each class, 32–bit and 64–bit.
The SGS_SUPPORT environment variable can be specified with a _32 or _64 suffix, and the link-editor options -z ld32 and -z ld64 can be used to define -S option requirements. These definitions will only be interpreted, respectively, by the 32–bit or 64–bit class of the link-editor. This enables both classes of support library to be specified when the class of the link-editor might not be known.