Diffrerence between position independent code and Relocatable code?

eshwar_ind · 05-10-2004, 01:24 AM

Can any body explain me the defferences between position independent code and relocatable code? And one more Question what is pure code How is it related to Position independent code ?
Thank you very much.
Bye,
Eshwar.

robkg · 05-10-2004, 03:49 AM

The difference is IIRC that relocatable code is produced by the compiler and can be relocated by the linker, you have also dynamic relocatable code that can be relocated during load-time linking by ld.so.
Position independent code is just a term for code that can run in any address space, the code doesn't have to be relocated, so the addresses don't have to be relocated because the code uses other mechanisms like using offsets instead of absolute addresses (for example, offsets from %esp on x86).

eshwar_ind · 05-10-2004, 09:30 AM

I didnt get Can you please explain me with a simple example.( C code )
Thanks for your reply.
Bye,
Eshwar

shishir · 05-10-2004, 11:37 AM

i'd suggest you try reading this book called linkers and loadeers by John Levine..
freely available at : http://www.iecc.com/linker/

nodger · 05-10-2004, 08:24 PM

Quote:

Q: what is the square root of 4b^2?

2b

eshwar_ind · 05-10-2004, 10:50 PM

Thank you very much.
Really it seems to be very good book.
Thanks once again.
Bye,
Eshwar.

shishir · 05-11-2004, 12:05 AM

Q: what is the square root of 4b^2?
2b or -2b ,(to be or not to be)

robkg · 05-11-2004, 01:40 AM

This is also a nice article to read on the subject.. it explains linking using a debugger;

http://duho.hackaholic.org/pub/ELF-LIB-UNFINISHED.txt