The role of the linker

The linker resolves symbols to addresses, nothing more
Symbols are in the input object files
And unresolved symbols are in there, too

It uses (or discards) input object files as a whole

It then reassembles ELF sections
It does so according to the linker script
Each ELF section is an atomic item
The same-name sections of different input files are merged
Originally, this was only .text, .code and .bss

Eventually, it can discard any sections not referenced to
This is what happens with "--gc-sections"
This is usually after "-ffunction-sections" in the compiler

Discarding unused sections is useful in the uC world
Similar functions live in the same file, like strcpy() and strcmp()