On 05/25/2011 11:36 AM, Ingo Molnar wrote:
So can other portability problems be solved, such as linker scripts
can be written for non-ELF targets (should that ever become
necessary)
I know that's not going to be the case, and I mentioned that in my first
message---portability is not relevant to tools/kvm/ just like it is not
relevant say to systemd.
so what's your point?
Using this kind of trick makes it harder to share code with other
libraries that may require a higher standard of portability (not
"better" or "worse", just "higher"). QEMU _does_ have this problem BTW,
we have our own event loop and AIO, our own JSON parser, our own thread
abstractions, and so on...
We want to use ELF sections in the future *anyway* to make
tools/kvm/ scale even better, for example to use alternative
instruction fixups (for which no GCC extension exists) so a linker
script will be there anyway.
Since you're not writing the hypervisor, but only the device model, I
doubt that this is needed (and you'd likely run into troubles with
SELinux). QEMU scales to dozens of VCPUs with a big lock around all
userspace device model code. But it's premature to say that, and I'd be
happy if I were proven wrong.
Fact is that neither ((section)) *NOR* ((constructor)) is portable:
*both* are GCC extensions - while you falsely claimed that
((constructor)) was somehow portable and that ((section)) was an
'unportable trick'.
Fair enough. I agree that ((constructor)) has limited scope and is
compiler-unportable. ((section)) is more powerful and has the cost of
using also target-unportable linker scripts, and requiring changes to
the build system. Both have the same problem with static libraries
(please reread my message).
I know portability is not relevant to tools/kvm/, but
using unportable tricks for the sake of using them is a
direct way to NIH. But oh well all of tools/kvm/ is NIH
after all. :)
Btw., that NIH claim was rather unfair and uncalled for as well.
Hey hey I put a smiley for a reason!
Anyway I think we both agree that this debate is pointless. I learnt
something (I wasn't aware of interaction between ((constructor)) and
static libraries), you learnt something (it's the same with ((section)),
and it's intrinsic in how static libraries work).
Paolo
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