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[[ libscript ]] Add Objective-C block support
This patch adds support for lcb scripts to use Objective-C blocks. Two handlers have been added to the Objective-C library, allowing for the creation and deletion of block pointers.
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2 files changed

Lines changed: 209 additions & 1 deletion

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‎libscript/src/objc.lcb‎

Lines changed: 208 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -610,4 +610,212 @@ public handler CreateObjcInformalDelegateWithContext(in pProtocol as List, in pH
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end unsafe
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end handler
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/* Block handling */
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private variable mNSConcreteGlobalBlock as optional Pointer
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private constant kRTLD_LAZY is 1
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private type LibraryHandle is Pointer
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private foreign handler OpenLibrary(in pPath as ZStringUTF8, in pFlag as CSInt) \
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returns optional LibraryHandle \
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binds to "dlopen"
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private foreign handler GetSymbolPointer(in pHandle as LibraryHandle, in pSymbol as ZStringUTF8) \
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returns optional Pointer \
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binds to "dlsym"
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private foreign handler CloseLibrary(in pHandle as LibraryHandle) \
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returns CSInt \
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binds to "dlclose"
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/* Fetch the `isa` pointer for the (internal) Obj-C concreate block class */
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private unsafe handler EnsureNSConcreteGlobalBlock() returns nothing
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if mNSConcreteGlobalBlock is not nothing then
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return
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end if
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/* As we cannot bind to the pointer to a symbol as a variable, we use
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* dynamic library loading and resolution functions to do so directly. */
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variable tSystem as LibraryHandle
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put OpenLibrary("libSystem.dylib", kRTLD_LAZY) into tSystem
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if tSystem is not nothing then
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put GetSymbolPointer(tSystem, "_NSConcreteGlobalBlock") \
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into mNSConcreteGlobalBlock
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CloseLibrary(tSystem)
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end if
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end handler
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private constant kBlockSize is 32
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private constant kBlockDescriptorSize is 40
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public foreign type _ObjcBlockDescriptor binds to "MCAggregateTypeInfo:ffrrr"
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public foreign type _ObjcBlock binds to "MCAggregateTypeInfo:rEErr"
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public type ObjcBlockPointer is Pointer
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foreign handler MCHandlerGetFunctionPtr(in pHandler as any, out rPtr as Pointer) \
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returns CBool \
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binds to "<builtin>"
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private foreign handler CopyBlockDescriptor(inout pBlock as _ObjcBlockDescriptor, in pSize as UIntSize, out rNewBlock as Pointer) \
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returns CBool \
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binds to "MCMemoryAllocateCopy"
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private foreign handler CopyBlock(inout pBlock as _ObjcBlock, in pSize as UIntSize, out rNewBlock as Pointer) \
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returns CBool \
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binds to "MCMemoryAllocateCopy"
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private foreign handler MCMemoryDelete(in pBlock as Pointer) \
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returns nothing \
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binds to "<builtin>"
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private foreign handler BlockPointerToBlock(out rBlock as _ObjcBlock, in pPointer as ObjcBlockPointer, in pSize as UIntSize) \
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returns nothing \
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binds to "c:memcpy"
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/**
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Create an Objective-C block pointer that wraps an LCB handler.
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Example:
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private variable sRequestPermissionsCompletionHandler as optional ObjcBlockPointer
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private variable sTarget as ScriptObject
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public handler AudioLibraryInitialize() returns Boolean
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if not CreateObjcBlockPointerFromHandler(RequestPermissionsCompletionHandler, sRequestPermissionsCompletionHandler) then
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put nothing into sRequestPermissionsCompletionHandler
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return false
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end if
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put the caller into sTarget
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return true
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end handler
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private foreign handler ObjC_AVCaptureDeviceRequestAccessForMediaType(in pMediaType as ObjcId, in pCompletionHandler as ObjcBlockPointer) \
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returns nothing \
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binds to "objc:AVCaptureDevice.+requestAccessForMediaType:completionHandler:"
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public handler AudioLibraryRequestPermissions()
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unsafe
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ObjC_AVCaptureDeviceRequestAccessForMediaType(StringToNSString("soun"), sRequestPermissionsCompletionHandler)
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end unsafe
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end handler
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public handler RequestPermissionsCompletionHandler(in pBlock as ObjcBlockPointer, in pGranted as CBool)
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post "AudioLibraryRequestPermissionsCallback" to sTarget with [pGranted]
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end handler
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Parameters:
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pHandler: The handler the block pointer should wrap.
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rBlockPtr: The variable into which the block pointer should be returned.
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Returns:
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True if the block pointer was successfully created, false otherwise.
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Description:
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Use the <CreateObjcBlockPointerFromHandler> handler to create a pointer to an
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Objective-C block that wraps an LCB handler. The block pointer can be used in
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calls to Objective-C foreign functions that expect a block as a parameter.
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The wrapped handler will be called whenever the block is invoked, with the first
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parameter of its signature being the block pointer. The remaining parameters
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should match those of the Objective-C block.
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The lifetime of a created `ObjcBlockPointer` is not automatically managed. When
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such a value has no more references to it and it is no longer going to be used,
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<DeleteObjcBlockPointer> should be used to free the resources used by it.
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References:
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DeleteObjcBlockPointer (handler)
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*/
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public handler CreateObjcBlockPointerFromHandler(in pHandler as any, out rBlockPtr as optional ObjcBlockPointer) returns Boolean
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variable tBlockPtr as ObjcBlockPointer
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unsafe
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/* Make sure the `isa` pointer has been initialized */
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EnsureNSConcreteGlobalBlock()
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/* Fetch the (C) function pointer for the given handler - this is used
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* later when constructing the block's record and is called when the
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* block is invoked. */
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variable tFunctionPtr as Pointer
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if not MCHandlerGetFunctionPtr(pHandler, tFunctionPtr) then
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return false
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end if
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/* Initialize the list of block descriptor aggregate members. The first
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* field is the flags where 0 means global block; the second field is
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* the size of the block record; the other members are not used (for our
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* purposes). */
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variable tBlockDescriptor as _ObjcBlockDescriptor
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put [0, kBlockSize, nothing, nothing, nothing] into tBlockDescriptor
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/* Copy the block descriptor after being (implicitly) converted to an
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* aggregate into a heap allocated memory block. */
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variable tBlockDescriptorPointer as Pointer
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if not CopyBlockDescriptor(tBlockDescriptor, \
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kBlockDescriptorSize, \
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tBlockDescriptorPointer) then
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return false
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end if
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/* Initialize the list of block members. The first field is the obj-c
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* objects 'isa' pointer; the second is the flags word; the third is
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* unused for our purposes; the fourth is the (C)function pointer it
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* wraps; and the fifth is the block descriptor (which mainly defines
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* the actual size of the block - as we don't add any block variables,
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* this is a fixed size. */
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variable tBlock as _ObjcBlock
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put [mNSConcreteGlobalBlock, \
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0x30000000, \
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0, \
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tFunctionPtr, \
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tBlockDescriptorPointer] into tBlock
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/* Copy the block after being (implicitly) converted to an aggregate
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* into a heap allocated memory block. */
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if not CopyBlock(tBlock, kBlockSize, tBlockPtr) then
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MCMemoryDelete(tBlockDescriptorPointer)
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return false
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end if
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end unsafe
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put tBlockPtr into rBlockPtr
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return true
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end handler
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/**
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Delete an Objective-C block pointer.
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Example:
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public handler AudioLibraryFinalize()
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if sRequestPermissionsCompletionHandler is not nothing then
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DeleteObjcBlockPointer(sRequestPermissionsCompletionHandler)
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put nothing into sRequestPermissionsCompletionHandler
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end if
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end handler
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Parameters:
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pBlockPointer: An Objective-C block pointer created with
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<CreateObjcBlockPointerFromHandler>
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Description:
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Use the <DeleteObjcBlockPointer> handler to delete an Objective-C block pointer
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created with <CreateObjcBlockPointerFromHandler>
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References:
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CreateObjcBlockPointerFromHandler (handler)
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*/
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public handler DeleteObjcBlockPointer(in pBlockPointer as ObjcBlockPointer)
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unsafe
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/* Unpack the pointer to block aggregate as an aggregate. */
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variable tBlock as _ObjcBlock
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BlockPointerToBlock(tBlock, pBlockPointer, kBlockSize)
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/* Delete the block's descriptor (fifth field). */
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MCMemoryDelete(tBlock[5])
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/* Delete the block itself. */
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MCMemoryDelete(pBlockPointer)
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end unsafe
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end handler
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end module

‎libscript/stdscript-sources.gypi‎

Lines changed: 1 addition & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -28,7 +28,6 @@
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'src/stream.lcb',
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'src/string.lcb',
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'src/system.lcb',
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'src/objc.lcb',
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'src/type.lcb',
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'src/type-convert.lcb',
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'src/unittest.lcb',
@@ -37,6 +36,7 @@
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'stdscript_other_lcb_files':
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[
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'src/objc.lcb',
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'src/unittest-impl.lcb',
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],
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