Start documenting the Objective-C ABI by jacob-carlborg · Pull Request #7923 · dlang/dmd

jacob-carlborg · 2018-02-20T16:14:50Z

This does not include the complete ABI, only what's necessary to call instance methods and class methods. This document will be extended when additional features are added.

dlang-bot · 2018-02-20T16:14:51Z

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jacob-carlborg · 2018-02-20T16:17:43Z

@JinShil @ibuclaw @WalterBright @wilzbach @UplinkCoder please have a look.

JinShil

I can't say I understand all of this, but if I were maintaining the Objective-C features of DMD, I think it would come in handy. My review is mostly just a bunch of nits.

JinShil · 2018-02-22T08:20:54Z

docs/objective-c_abi.md

+from implementation stand point is that in D and C++ a vtable is used which
+is an array of function pointers and the compiler uses an index into that array
+to determine which method to call. In Objective-C it's the runtime that is
+responsible to find the correct implementation when a message is sent to an


s/to find/for finding

JinShil · 2018-02-22T08:22:59Z

docs/objective-c_abi.md

+int result = objc_msgSend(receiver, selector);
+```
+
+If the method expects any arguments they're passed after the selector argument:


s/they're/it's

But arguments is plural?

Sorry, I don't know what I was thinking. Just ignore anything stupid in my comments.

JinShil · 2018-02-22T08:23:53Z

docs/objective-c_abi.md

+id objc_msgSend(id self, SEL op, ...);
+```
+
+* The first parameter is the receiver (this/self pointer)


should "this" and "self" be surrounded by tick marks?

JinShil · 2018-02-22T08:26:43Z

docs/objective-c_abi.md

+
+The call to `objc_msgSend` should not be performed as a variadic call but
+instead as if it had the same signature as the method that should be called but
+with the two additional parameter, `self` and `op`, added first. The


That first sentence is a little hard to follow. Maybe it can be rephrased.

I changed it slightly, but I'm not sure if it's any better. Writing is not my strongest skill. Suggestions are welcome.

JinShil · 2018-02-22T08:28:28Z

docs/objective-c_abi.md

+implementation of `objc_msgSend` will jump to the method instead of calling it.
+
+Because of the above, multiple versions of `objc_msgSend` exist. Depending on
+the return type of the method that is called the correct version need to be


comma after "called".

s/the correct version need to be used/the correct version will be used

JinShil · 2018-02-22T08:36:33Z

docs/objective-c_abi.md

+
+For each selector that is used, a symbol is generated in the resulting binary.
+The symbol has the name `L_OBJC_METH_VAR_NAME_.<number>`, where `<number>` is an
+incrementing number. The selector is stored as a null terminated C string as the


s/as the section data/in the data section?

Not sure how to best describe it but the data stored in this section is the selector.

JinShil · 2018-02-22T08:37:43Z

docs/objective-c_abi.md

+For each externally defined class that is referenced, a symbol is generated in
+the resulting binary. The symbol has the name
+`L_OBJC_CLASSLIST_REFERENCES_$_.<number>`, where `<number>` is an incrementing
+number. The content of the symbols is a reference to an externally defined


Should "symbols" be singular here?

JinShil · 2018-02-22T08:38:21Z

docs/objective-c_abi.md

+
+### `L_OBJC_IMAGE_INFO`
+
+For any binary that is built the `L_OBJC_IMAGE_INFO` symbols is generated. The


comma after built?

JinShil · 2018-02-22T08:39:19Z

docs/objective-c_abi.md

+
+Indicates if features like: garbage collector, automatic reference counting
+(ARC) or class properties are supported. These features can be enabled/disabled
+in the Clang compiler using command line switches. The exact values used or the


comma after "used" and "supported"?

JinShil · 2018-02-22T08:40:12Z

docs/objective-c_abi.md

+
+## Tools
+
+Here follows a list of useful tools that can/has been used to get the


This does not include the complete ABI, only what's necessary to call instance methods and class methods. This document will be extended when additional features are added.

jacob-carlborg · 2018-02-22T11:43:35Z

Fixed all comments, except two, where I asked for more input.

jacob-carlborg · 2018-03-05T17:11:19Z

@JinShil @wilzbach can we please merge this as well. #7762 is already merged.

jacob-carlborg mentioned this pull request Feb 20, 2018

Add support for Objective-C class/static methods #7762

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JinShil approved these changes Feb 22, 2018

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Start documenting the Objective-C ABI

696f41b

This does not include the complete ABI, only what's necessary to call instance methods and class methods. This document will be extended when additional features are added.

jacob-carlborg force-pushed the objc_abi_docs branch from a896506 to 696f41b Compare February 22, 2018 11:11

JinShil approved these changes Feb 28, 2018

View reviewed changes

JinShil added the Merge:72h no objection -> merge The PR will be merged if there are no objections raised. label Feb 28, 2018

JinShil added the Merge:auto-merge label Mar 5, 2018

dlang-bot merged commit d8642fe into dlang:master Mar 5, 2018


		### `L_OBJC_IMAGE_INFO`

		For any binary that is built the `L_OBJC_IMAGE_INFO` symbols is generated. The


		## Tools

		Here follows a list of useful tools that can/has been used to get the

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jacob-carlborg commented Feb 20, 2018

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dlang-bot commented Feb 20, 2018

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jacob-carlborg commented Feb 20, 2018

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jacob-carlborg commented Feb 22, 2018

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jacob-carlborg commented Mar 5, 2018 • edited Loading Uh oh! There was an error while loading. Please reload this page.

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jacob-carlborg commented Mar 5, 2018 •

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