Position-Independent Code and -pic

Position-independent code (PIC) can be bound to any address in a program without requiring relocation by the link editor. Such code is inherently sharable between simultaneous processes. Thus, if you are building a dynamic, shared library, you must compile the component routines to be position-independent (by using compiler options -pic or -PIC).

In position-independent code, each reference to a global item is compiled as a reference through a pointer into a global offset table. Each function call is compiled in a relative addressing mode through a procedure linkage table. The size of the global offset table is limited to 8 Kbytes on SPARC processors. The -PIC compiler option is similar to -pic, but -PIC allows the global offset table to span the range of 32-bit addresses.

Version 5.0 of f77 and version 2.0 of f90 introduce a more flexible compiler flag, -xcode=v, for specifying the code address space of a binary object. With this compiler flag, 32-, 44-, or 64-bit absolute addresses can be generated, as well as small and large model position-independent code. -xcode=pic13 is equivalent to -pic, and -xcode=pic32 is equivalent to -PIC. See the f77(1) and f90(1) man pages, or the Fortran User's Guide, for details.