On 06/24/2011 11:53 AM, Agner Fog wrote: > On 24-06-2011 12:38, Andrew Haley wrote: >> On 06/24/2011 11:19 AM, Agner Fog wrote: >>> On 24-06-2011 10:23, Andrew Haley wrote: >>>> >>>>> Why does it make 32 bit absolute addresses when I specify >>>>> -mcmodel=medium? >>>> Small symbols are placed in the lower 2G. >>> So I would have to replace all variables with very big arrays in order >>> to prevent 32 bit addresses in 64 bit mode :-( >> What problem are you trying to solve? I don't get it. Why would you >> want to avoid 32-bit absolute addresses? >> > Because the linker complains whenever there is a 32 bit absolute > reference in a 64 bit shared object. I guess the .so can be loaded above > the 2G address limit. Can you show us how you made a 64-bit absolute reference in a shared object? I don't quite understand how that could work. Apart from anything else, I don't think the x86_64 has instructions to do it. > Apparently, the only way to avoid 32 bit addresses is compiling with > -fpic, which has the undesired effect of using GOT and PLT entries which > makes shared objects slower than static libraries. The seldom used > feature to override a symbol comes at a high price. Its isn't seldom used. It's used all the time. If it weren't possible to override symbols in shared libraries, every user of a library would be forbidden to use any of the symbols exported by that library in their own programs. Andrew.
