Re: -fPIC for libnetdissect

[Guy Harris <guy () alum mit edu>]

On Oct 30, 2016, at 9:18 AM, Michael Richardson <mcr () sandelman ca> wrote:

> When building libnetdissect into a virtual switch (uml_netjig), I started to
> get:
>   /usr/bin/ld: /home/mcr/stuff/x86_64/tcpdump-4.8.1/libnetdissect.a(print-ripng.o): relocation R_X86_64_32 against 
> `.rodata' can not be used when making a shared object; recompile with -fPIC
>
> which is odd, since I'm not trying to make a shared object, just a final link
> of the executable.  But, adding -fPIC to the build works.
>
> a) any reason we shouldn't build with -fPIC when using gcc?

Well, there might be platforms on which -fpic would be sufficient, but -fPIC appears to be necessary for x86-64 - and I 
wouldn't be surprised if it's necessary on SPARC as well.

> b) any advince in a way that doesn't shoot non-gcc builds in the foot?

We could pick up the stuff in libpcap for building *it* as a shared library, and adjust as necessary for netdissect, 
e.g. adding x86-64 (at least on some OSes) to the set of platforms where we need -fPIC.
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