How can you determine optimization level from file?

Question

I have a compiled elf file and I would like to verify the optimisation level used. The question is how can I determine optimisation level from an object/elf?

I have tried with "file" command and "objdump" (most of the switches), but none of them revealed this. Is it possible at all?

Answer 1

strings foo.o | grep -- -O might give you what you want.

Answer 2

No, not in general. The compiler doesn't write its active "optimisation" setting to the object file, and it's not necessarily possible to determine from the object code itself.