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Re: crash upon startup in GWorkcenter, Recycler, ProjectCenter and Gorm


From: Ivan Vučica
Subject: Re: crash upon startup in GWorkcenter, Recycler, ProjectCenter and Gorm
Date: Fri, 29 Dec 2017 20:42:59 +0000

> On 29 Dec 2017, at 05:56, Josh Freeman <address@hidden> wrote:
>  When using the nonfragile ABI, the compiler emits code that calculates ivar 
> offsets using global variables - there's a global for each ivar, using the 
> naming convention:
> __objc_ivar_offset_[CLASS_NAME].[IVAR_NAME]
> 
>   For example, NSThread's _gcontext has a corresponding global in the emitted 
> code named, "__objc_ivar_offset_NSThread._gcontext".
> 
>   Nonfragile-ABI-compiled code calculates the address of an object's ivar by 
> adding the value of the ivar's __objc_ivar_offset* global to the object's 
> address.

This whole analysis is (like David’s work on the runtime and the compiler) 
black magic and wizardry — and reading it is an excellent learning experience.

Thank you for the writeup!

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