Relocation (computing)

Since multiprocessing systems dynamically link and switch between programs it became necessary to be able to relocate objects using position-independent code.

The relocation table is a list of pointers created by the translator (a compiler or assembler) and stored in the object or executable file.

Each entry in the table, or "fixup", is a pointer to an absolute address in the object code that must be changed when the loader relocates the program so that it will refer to the correct location.

For both DLLs and for EXEs which opt into address space layout randomization (ASLR), an exploit mitigation technique introduced with Windows Vista, relocation tables once again become mandatory because of the possibility that the binary may be dynamically moved before being executed, even though they are still the first thing loaded in the virtual address space.

When running native 64-bit binaries on Windows Vista and above, ASLR is mandatory[citation needed], and thus relocation sections cannot be omitted by the compiler.