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Presumably, as an implementor of an Objective-C compiler, I would choose how to compile methods, and I might just choose to compile methods to functions taking

Presumably, as an implementor of an Objective-C compiler, I would choose how to compile methods, and I might just choose to compile methods to functions taking (something memory-compatible with) va_list.

icodestuff 9y ago
But then you can't call those methods from C yourself (expecting va_list, received arguments). And what about adding methods to classes from plain C functions? Do you duplicate those functions with a va_list version? Seems like that'll add quite a bit of bloat.
- tom_mellior 9y ago
  <shrug> I corrected a post saying "X is impossible in C". That's a different issue from whether X is as efficient in C as in assembly language.
  - chrisseaton 9y ago
    I think the point was that you cannot implement this particular function in C - a function that forwards arguments to other functions, given a particular standard ABI. You've changed the requirements by saying that now the other functions use a different ABI, so you've missed the point of why it's impossible to implement this function, in these circumstances, in C.
    - tom_mellior 9y ago
      The original question in this thread was whether it was really impossible, under any circumstances, to write this in C, as part of an Objective-C implementation that you fully control. It is possible in C, if you can control the ABI. It's the people who insist on a particular pre-existing ABI who are changing the question. Anyway, I think I've said all I'm going to say here.
plorkyeran 9y ago
The functions which are called by objc_msgSend do not have to be methods compiled by an obj-c compiler. You can add functions compiled by a compiler with no knowledge of or support for obj-c to an obj-c class at runtime, and then call that method via objc_msgSend. Obviously you could come up with other ways of passing arguments to obj-c methods which would make it possible to implement your message send function in pure C, but a message send function which passes the arguments as a va_list is not objc_msgSend(), and that says nothing about whether or not objc_msgSend() could be implemented for the design they did go with in pure C.

icodestuff 9y ago

But then you can't call those methods from C yourself (expecting va_list, received arguments). And what about adding methods to classes from plain C functions? Do you duplicate those functions with a va_list version? Seems like that'll add quite a bit of bloat.

tom_mellior 9y ago
<shrug> I corrected a post saying "X is impossible in C". That's a different issue from whether X is as efficient in C as in assembly language.
- chrisseaton 9y ago
  I think the point was that you cannot implement this particular function in C - a function that forwards arguments to other functions, given a particular standard ABI. You've changed the requirements by saying that now the other functions use a different ABI, so you've missed the point of why it's impossible to implement this function, in these circumstances, in C.
  - tom_mellior 9y ago
    The original question in this thread was whether it was really impossible, under any circumstances, to write this in C, as part of an Objective-C implementation that you fully control. It is possible in C, if you can control the ABI. It's the people who insist on a particular pre-existing ABI who are changing the question. Anyway, I think I've said all I'm going to say here.

plorkyeran 9y ago

The functions which are called by objc_msgSend do not have to be methods compiled by an obj-c compiler. You can add functions compiled by a compiler with no knowledge of or support for obj-c to an obj-c class at runtime, and then call that method via objc_msgSend. Obviously you could come up with other ways of passing arguments to obj-c methods which would make it possible to implement your message send function in pure C, but a message send function which passes the arguments as a va_list is not objc_msgSend(), and that says nothing about whether or not objc_msgSend() could be implemented for the design they did go with in pure C.