Re: [PATCH 5/5 V2] kvm tools: Initialize and use VESA and VNC

[Ingo Molnar <mingo@elte.hu>]

* Paolo Bonzini <pbonzini@redhat.com> wrote:

> > 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"). [...]

That's an complication but should be fixable, should it ever happen.

As things stand today we:

 - Are *already* using an ELF linker script, see tools/kvm/bios/rom.ld.S

 - Have multiple valid reasons not to use ((constructor))

 - Want to use sections to implement other useful features as well

If the *only* linker script use would be the init facility then you'd 
probably have a valid point - although the possible code flow 
fragility with ((constructor)) is still a problem: we still would 
want to know when no constructors were executed.

Also it's not clear why ((constructor)) was written in the way it 
was: why apparently no access is given to the array of init functions 
and why it's not possible to turn the auto-execution off but still 
have the array generated, for legitimate cases that want to use data 
driven constructor execution.

> >>>>>> 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!

Well after two insults in a single paragraph you need to put in at 
least two smileys! Or not write the insults in a technical discssion 
to begin with, especially if you are criticising a patch rather 
forcefully. It will be easily misunderstood as a real insult, despite 
the smiley ;-)

> 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).

While i did not know whether static libraries would work with a 
linker script (never tried it - and your experiment suggests that 
they wont), the ((section)) approach we could create a clear runtime 
BUG_ON() assert for a zero-sized array of init function pointers, 
while ((constructor)) will silently not execute initialization 
functions.

Thanks,

	Ingo