On 15.11.2014, at 22:28, Igor Stasenko <siguctua@gmail.com> wrote:

On 15 November 2014 15:53, Max Leske <maxleske@gmail.com> 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?