Re: Compiling on Darwin

[David Ayers]

John Davidorff Pell wrote:

> I'm now compiling apple's gcc  with the patch in the machine-specific 
> instructions (change #define to  #undef), but I am unwilling to trash 
> my NeXT runtime, how do i install  the GNU runtime (and why isn't it 
> built by default? Even if disabled!?)  without clobbering other stuff, 
> and what does  -fgnu-runtime/-fnext-runtime *actually* do?

You could have a look at the following bug report against gcc:
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=11572

They way I understand the situation is that -fgnu-runtime/-fnext-runtime 
are only /indicators/ for the compiler for which runtime to emit code.  
It has no control over which runtime the code will actually be linked 
against or which runtime the dynamic loader will find at runtime.

It depends on what you mean by "clobbering".  If you don't specify any 
special prefix when installing libobjc manually,  I /believe/ it will be 
installed in /usr/local instead of /usr therefore not overwriting the 
apple runtime but (most likely) hiding it in the sense that /usr/local 
may (or should) be preferred in searches.  That could be the case for 
linker, loader and the header search for gcc itself.  (i.e. which 
runtime is meant by #include <objc/objc.h>)

Now there are ways to configure gcc to prefer it's *own* header files 
(if libobjc is build together with gcc which isn't possible with all 
versions of gcc on Darwin anymore).  Some people believe that 
-fgnu/runtime/-fnext-runtime should include some more magic for linker 
and loader also (well I guess it would only be needed for the Darwin 
implementations of them).

Personally I think that trying to obfuscate the complexity of having two 
runtimes with the same name on one system is a questionable approach.  I 
attached a patch to the bug report that would give the gnu runtime a 
different name for the linker/loader and rely on the existing gcc header 
search mechanics to find it's *own* libobjc (which would be the gnu 
version), but the patch hasn't been greeted with a lot of acceptance 
:-).  I /believe/ the main reason being that there is an expectation for 
Apple to solve this by tweaking their linker/loader.

Hopefully that helps you understand the situation a bit better.

Cheers,
David