How do linkers manage relocation in program execution?

Linkers manage relocation in program execution by adjusting the absolute addresses of code and data segments to run at different locations.

In more detail, linkers play a crucial role in the process of program execution. They are responsible for combining various pieces of code and data into a single file that can be loaded into memory and executed. One of the key tasks of a linker is to manage the relocation of these code and data segments. This is necessary because a program may not always be loaded into the same location in memory each time it is run.

Relocation involves adjusting the absolute addresses of code and data segments so that they can be correctly referenced at runtime. This is done using a process known as 'relocation linking'. The linker maintains a table of relocation entries, each of which corresponds to a specific symbol in the program. These symbols could be variables, functions, or any other identifiable piece of code or data. Each entry in the relocation table contains information about the symbol, including its name, its location in the original code, and the type of relocation required.

When the program is loaded into memory, the linker uses the relocation table to adjust the addresses of the symbols. This involves adding the base address of the memory location where the program is loaded to the original address of the symbol. This results in a new, relocated address that correctly references the symbol in its new location in memory.

The linker also has to update any references to these symbols in the code. This is done by scanning through the code and replacing each reference to a symbol with its new, relocated address. This ensures that the code correctly references the relocated symbols, regardless of where the program is loaded into memory.

In summary, the linker manages relocation in program execution by adjusting the absolute addresses of code and data segments and updating references to these segments in the code. This allows the program to run correctly at different locations in memory, providing flexibility and efficiency in program execution.