[inkyoto]

> Just to add to what you said: in the old days the linker would include only the .o files in the .a library that were referenced.

It was not exactly like that. Yes, the .o file granularity was there but the unused code from that .o file would also get linked in.

The original UNIX linker had a very simple and unsophisticated design (compared to its contemporaries) and would not attempt to optimise the final product being linked. Consider a scenario where the binary being linked references A from an «abcde.o» file, and the «abcde.o» file has A, B, C, D and E defined in it, so the original «ld» would link the entire «abcde.o» into the final product. Advanced optimisations came along much later on.