Re: "undefined reference to ’objc_msgSend’"

[David Chisnall]

On 04/04/2019 17:46, Marcus Müller wrote:
> > On 4. Apr 2019, at 15:28, David Chisnall <gnustep@theravensnest.org 
> > <mailto:gnustep@theravensnest.org>> wrote:
> >
> > On 04/04/2019 13:52, Scott Little wrote:
> > > →    -L/usr/lib/gcc/x86_64-linux-gnu/7/libobjc.so \
> >
> > This looks very much as if you are linking the old GCC libobjc, which 
> > doesn't provide an objc_msgSend implementation.  If you wish to use 
> > this, then you must use -fobjc-runtime=gcc, not -fobjc-runtime=gnustep.
> >
> > -fobjc-runtime=gnustep is not recommended without an explicit version 
> > (e.g. -fobjc-runtime=gnustep-2.0).
>
> I usually select the runtime by defining `RUNTIME_VERSION`, i.e. 
> `RUNTIME_VERSION=gnustep-2.0`. Scott wrote, however, that he's using 
> clang-3.9. If I understood the previous conversation correctly, then 
> you'd need at least clang-7.0 in order to use the 2.0 ABI, correct? What 
> happens in this case? Will clang (somehow) downgrade the runtime 
> features to the maximum version it supports?

Clang will only use the features of the newest version that it knows 
about.  In clang 7 and newer, there's now a macro so you can detect the 
degree to which it's downgraded, but that won't be set with such an old 
version of clang.  It should support the 1.8 ABI though, which should be 
good enough...

David