Re: Package building

[David Chisnall]

On 20/11/2019 11:07, Andreas Fink wrote:
> is libobjc even supporting all these other platforms?

The GCC runtime is written in pure C and so should work everywhere that 
there's a C compiler.  The GNUstep runtime uses assembly to implement 
two features that can't be implemented in pure C:

objc_msgSend
imp_implementationWithBlock

Both of these need to modify the call frame and then pass all of the 
arguments unmodified, which C doesn't support.

In theory, you should be able to use the runtime without these features, 
but I'm not sure if it actually builds (happy to take patches to fix that).

KVO is *significantly* simpler to implement with 
imp_implementationWithBlock, so it would be nice if we could depend on 
that.  objc_msgSend is largely a performance optimisation (clang uses it 
only on platforms where it's supported).

I'm happy to take contributions for the assembly paths for other 
architectures.  We currently have:

- x86-32
- x86-64
- AArch32
- AArch64
- MIPS (at least n64 works, I think o32 and n32 are there but untested).

I passionately hate PowerPC assembly, so will definitely not write that 
myself, but anyone who wants to add it is very welcome to do so.  I will 
probably get around to adding RISC-V support at some point.

David