Re: Clang/LLVM migration roadmap

[Riccardo Mottola]

Hi,

On 2022-02-06 10:51:49 +0000 Richard Frith-Macdonald <rfm@gnu.org> 
wrote:


> I think general portability is an issue, not just MSYS.

MSYS is very sensitive itself - it took 2 years of work to upgrade 
from the original "msys 1" setup with gcc 3.4 (all newer gcc's had 
subtle issues!) to a failry decent setup withh current GCC and 32bit 
and 64bit support - and we did it so well we didn't even break the old 
toolchain!

> Yes, there's the issue of architecture specific code in the runtime,  
> but 
> additionally I have seen two problem areas:

Stacks and exceptions are architecture and OS dependent. Also libobjc2 
interoperates with C++, making it more powerful but alsso complex 
compared to the gcc libobjc1 runtime


> 1. building libobjc2
> a. dependency on cmake and ninja ... easy to find packages for most 
> systems, 
> but definitely an annoyance

I think this is the easiest part to solve, actually - just boring, but 
I bet autoconf and make can be used as you did in the past yourself! A 
matter of defining the correct variables and settings. Why shouldn't 
both system coexist even?

> b. has failed to build with some compiler versions etc in the past, 
> so we 
> need to work out reliable toolchains for all platforms

Compilers and especially linkers. I used to have locu with the gold 
linker, but sometimes with the bgf, things are trial-and-error and not 
stable!
Also, the gold linker is not available on all platforms.

> 2. runtime errors
> I have had problems with getting things to run, the current one I am 
> aware of 
> is related to linker ... the runtime will fail with executable 
> produced by 
> common linkers under some conditions.  There also seems to be 
> problems with 
> C++ integration for exceptions and compiler bugs.
>
> I do use clang/libobjc2 on a daily basis on gnu/linux amd64 with no 
> problems 
> at all, but it took a long time to get the right toolchain in place. 
> We need 
> this to be less fragile, so people can update parts of their 
> toolchain 
> without breakign things.

I have it on FreeBSD/amd64 and Linux/intel32, both work but on both 
exceptions do not work properly.

Even without performing a "migration" a better libobjc2 setup, easier, 
more portable, would benefit all those wishing to use it.

I shall start documenting all these issues better though.

Riccardo

--
Proudly sent with GNUMail on GNUstep on FreeBSD/x86-64