Created
August 8, 2014 08:14
-
-
Save yuanshanxiaoni/02e261aedeafb6321b2e to your computer and use it in GitHub Desktop.
objc runtime bootstrap
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
| The runtime does some initialization via constructor functions that get called before actual program execution. They go by __attribute__((constructor)) in both gcc and clang. | |
| In the case of Objective-C some of them are embedded in the binary by the compiler. You would have to include them in your headers for similar effect. | |
| These functions use data automatically embedded by the compiler. They do things such as building hash tables for the class lookup function which are then used for the actual message passing. | |
| Instances on the other hand are allocated dynamically. | |
| I am doing something similar, so I don't really know a lot better than that, but this is as deep as I have dug. | |
| [https://stackoverflow.com/questions/2219501/how-does-the-objective-c-runtime-instantiate-the-root-metaclass-and-other-class] |
Author
Author
A module(.m file) constructor is a function that calls the runtime with a pointer to the compiler generated Module structure, which contains references to everything else.
Author
Of course, that is done for convenience, but if you had your class descriptions stored in data files you could build the structures you need from a file. The difference is that the compiled Objc generates structures that are readily usable by the runtime, so you would be doing that part of the work JIT.
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
there is a section of the binary called .ctors that contains a list of function pointers to be called. That list is written to by the compiler-linker from the list of functions which have a constructor attribute and executed either at the startup code if a static library or by the initialization code in dynamic linked files.