> On 15.11.2014, at 22:28, Igor Stasenko <[email protected]> wrote:
>
>
>
> On 15 November 2014 15:53, Max Leske <[email protected]
> <mailto:[email protected]>> wrote:
> Once again I’m struggling with NativeBoost. I’m trying to use
> optCoerceNilToNull with this function:
>
> ^self call: #(LGitReturnCodeEnum git_commit_create(
> LGitId * theCommitId,
> LGitRepository repo,
> String update_ref,
> LGitSignature * theAuthor,
> LGitSignature * theCommitter,
> String message_encoding,
> String theMessage,
> LGitTree theTree,
> int parent_count,
> LGitCommit * parentsPointer)) options: #( optCoerceNilToNull )
>
> The last argument can be NULL, per documentation, (no parents).
> LGitCommit is a subclass of NBExternalObject and apparently
> NBExternalObjctType>>pushAsPointer: does *not* use the optCoerceNilToNull
> option (the super implementation in NBExternalType>>pushAsPointer: however
> does). The upshot of course is that the call fails with “an instance of
> LGitCommit expected”.
>
> My questions:
> - The documentation says:
>
> "#optCoerceNilToNull"
> "passing nil as a pointer-type argument, converts it to C NULL “
>
> but apparently this doesn’t apply to every pointer type. Should the
> documentation be updated?
> - Why does NBExternlObjectType not use optCoerceNilToNull? I don’t want to
> use tricks to pass null if I don’t have to.
>
> perhaps because it is not there? :)
> So, lets add it.
Yay! :) I have zero assembly skills… I’ve tried the following but then get an
“undefined label done18” error:
NBExternalObject>>pushAsPointer: gen
"push a pointer to handle value"
| asm proxy oop notNil done |
proxy := gen proxy.
asm := gen asm.
<<<<<<<<<<<<<< new
done := asm uniqueLabelName: 'done’.
>>>>>>>>>>>>>>> new
oop := gen reserveTemp.
loader emitLoad: gen to: oop.
<<<<<<<<<<<<<< new
"handle nils, if we care"
gen optCoerceNilToNull
ifTrue: [
notNil := asm uniqueLabelName: 'notNil'.
proxy nilObject.
asm cmp: asm EAX with: oop;
jne: notNil;
xor: asm EAX with: asm EAX;
jmp: done;
label: notNil ]
ifFalse: [
"we can skip class verification, if loader loads
receiver, since nothing to fear there"
loader isReceiver ifFalse: [
self verifyClassOf: oop is: objectClass
generator: gen.
] ].
>>>>>>>>>>>>>>> new
proxy fetchPointer: (self handleIvarIndex) ofObject: oop. "handle ivar"
proxy varBytesFirstFieldOf: asm EAX. "handle value ptr"
asm push: asm EAX.
gen releaseTemps: 1.
>
> - Related: there are instances where even non-pointer arguments are allowed
> to be NULL. Why does optCoerceNilToNull only work for pointer types?
>
>
> like what? Suppose the argument type is a structure, e.g
> "struct foo bar", that is non-pointer type. What in this case the NULL value
> for the structure?
Ok, I think I understand. Are you saying that, since NULL is a macro, you have
no way of telling during runtime how NULL is defined? For a pointer it is
simply 0 or (void *) 0, but for a non pointer it depends on the context. Is
that about right?
>
> Igor! Help! :)
>
> Cheers,
> Max
>
>
>
>
> --
> Best regards,
> Igor Stasenko.
