[Bug ada/81878] --disable-bootstrap --enable-languages=ada fails

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81878

--- Comment #6 from Richard Biener <rguenth at gcc dot gnu.org> ---
(In reply to Richard Biener from comment #5)
> (In reply to Eric Botcazou from comment #3)
> > > I see.  I suppose it should use the build tools if not bootstrapping as well
> > > (and/or for stage1).  Isn't this all set up correctly from the toplevel make
> > > anyway?!
> > 
> > Do you mean that passing $(CXX) as in the cross case should work?
> 
> I would think so.  No other host library/tool dir does this kind of dance.
>
> Of course ada toplevel stuff is somewhat special...

As can be seen in the result:

make[3]: Entering directory '/tmp/obj/gcc/ada/tools'
gcc -c -g -O2 -W -Wall  -gnatpg -gnata -I- -I../rts -I. -I/tmp/trunk2/gcc/ada
../rts/s-casuti.adb -o s-casuti.o
s-casuti.adb:32:08: warning: unrecognized pragma "Compiler_Unit_Warning"
s-casuti.ads:40:08: warning: unrecognized pragma "Compiler_Unit_Warning"
../gcc-interface/Makefile:296: recipe for target 's-casuti.o' failed
make[3]: *** [s-casuti.o] Error 1

so the host ada compiler (gnat 4.8) doesn't work for this part.  With
cross-compiling we require a host compiler matching the target one, right?

> > > So I guess generally enabling C++ when enabling Ada would regress cross
> > > builds.
> > 
> > Yes, we would need to enable it only for native.