[Ada] Bootstrapping mainline GNAT fails (with workaround and root cause: makefile bug)

[Florian Weimer]

"lode_leroy at hotmail dot com" <"lode_leroy at hotmail dot com"@bemls8> writes:

> Then I tried building in a separate build tree but I got problems
> during linking of gnatlib:
>
>     c-charac.o not found
>
> After spending a some time reading the Makefiles and trying out
> various things, I found that the observed problems are caused by the
> file:
>
>     build/gcc/ada/Makefile
>
> which contains
>     VPATH=../../../gcc/ada
>
> When making in the directory
>     build/gcc/ada/rts
>
> the file build/gcc/ada/Makefile is used, as follows:
>     make -f ../Makefile
>
> When used like this, the relative directory in VPATH ends up pointing
> to the wrong directory.

Usually, this means that your build directory is located somewhere in
the source tree.  This setup is not supported by GCC at all, as
documented.  (This restriction is not specific to the Ada front end.)