Re: [Qemu-devel] [PATCH v10 5/8] module: implement module loading

[Richard Henderson <rth@twiddle.net>]

On 09/16/2013 04:46 AM, Fam Zheng wrote:
> On Mon, 09/16 13:33, Paolo Bonzini wrote:
>> Il 16/09/2013 13:29, Fam Zheng ha scritto:
>>> An idea for single .so file:
>>>     - before loads a .so, an empty initializer list is created.
>>>     - module_init adds a __attribute__((constructor)) function, which appends
>>>       its real initializer to the initializer list. So this function is
>>>       automatically called after dlopen().
>>>     - make init_$(date +%s$$$RANDOM) a dummy symbol.
>>>     - module_load first checks the presense of the symbol, if yes, call the
>>>       functions in the initializer list. Else clean up and unload .so.
>>>
>>> Does this enable multiple calls of module_init()?
>>
>> Yes.  Basically you are delaying the constructors; that would work.
>>
>>> OTOH. As for multiple spice modules, is it possible to solve it by having a
>>> spice-common.o and link all spice modules to it, to share code?
>>
>> Looks like there is global state in ui/spice-core.c, so likely no.
>>
> 
> What if the modules can be loaded by name? Then in spice-qemu-char.so, it can
> call require_module("spice-core") before initializing itself, which will load
> this dependency if not yet.  This may be the simplest implementation of
> dependency resolving.

Why oh why would you want to re-invent the dependencies that ld.so already
provides?

Link spice-qemu.char.so against spice-core.so.  The DT_NEEDED entry will be
recorded, and ld.so will do the right thing.

Anything else sounds way too much like Not Invented Here.


r~