Re: [omr-dev] ResolvedMethod question

[Leonardo <leonardo2718@xxxxxxxxxxxxxx>]

Hi Dibyendu,

> 
> On 11 June 2018 at 21:01, Dibyendu Majumdar mobile@xxxxxxxxxxxxxxx wrote:
> 
> > I am looking at how to register foreign functions or call a function
> > via pointer. Looking at MethodBuilder and ThunkBuilder I can see that
> > to call a function an instance of ResolvedMethod is needed. How is the
> > ResolvedMethod linked to the Code Cache? Is it stored anywhere - or is
> > it just an interface that must be defined for any callable function? I
> > presume that the list of foreign functions can be simply maintained by
> > the front-end?
> > 

The simple answer is that `TR::ResolvedMethod` is just the interface used to define a callable function. The compiler uses it to "construct" calls. If you haven't already done so, I would recommend taking a look at the implementations of MethodBuilder::DefineFunction(), IlBuilder::Call(), IlBuilder::ComputedCall(), and IlBuilder::genCall().

As a side note, when discussing "ResolvedMethod", it's important to distinguish between `TR::ResolvedMethod` and `TR_ResolvedMethod`. Sadly, both of these classes exist and are, in fact, different. I believe you only need to worry about `TR::ResolvedMethod`, at least for now. Just something to look out for when reading the code :-)

> On June 12, 2018 7:52 PM, Dibyendu Majumdar <mobile@xxxxxxxxxxxxxxx> wrote:
> ​​
> With regards to the question below - I have an additional question
> regarding memory and lifetimes. It seems that ResolvedMethod
> implementation accepts various pointers and holds on to them. But
> presumably does not free them as far as I can tell. What is the
> assumption here with regards to memory management?

Internally, the OMR compiler uses a custom memory manager to handle all allocation/deallocations (see https://github.com/eclipse/omr/blob/master/doc/compiler/memory/MemoryManager.md). As such, most (all?) APIs assume that any memory accessed using pointers is already managed and will not take ownership of it. So, to answer your question more directly, the pointers you provide a ResolvedMethod will not be freed. The memory for these pointers can be allocated/freed using the compiler's internal memory manager, but doing so is not required.

Hope that helps :-)

Regards,

--
Leonardo