Am 15.01.2014 um 11:49 schrieb Ingo Weinhold <ingo_weinhold@xxxxxx>:
I had a closer look at the clang setup and I think before continuing with the
jam part of the build system, the first step should be to set up a clang cross
compilation environment that no longer depends on gcc.
This is unfortunately not possible yet, I guess. Clang uses gcc as assembler
and linker. We can force Clang to use its own assembler using -integrated-as. I
already force the integrated assembler, as Clang currently blindly passes all
-f flags to the assembler as well, making it fail at flags like
-fheinous-gnu-extensions as GCC does not know them. However, that keeps the
linker. So, unless we change linking to using ld directly, we're stuck with
having a dependency on GCC 4.x for Clang.
This is unfortunate, but fixable in Clang itself. But that also means we need
to wait until the next Clang release. The problem exists for many platforms
which are not primary targets of Clang. E.g. on MinGW32, it also calls back
into the MinGW32 GCC as assembler and linker, which causes configure scripts to
fail if they use clang-only flags. So if we want to get GCC-free, we need to
teach Clang how to invoke the linker directly on Haiku. I think this is
something we should definitely in the future, and then raise our minimum Clang
version.
When it is clear how that can be done, the configure script should be adjusted to support clang. We'll probably
want to define a jam variable HAIKU_COMPILER_<arch> to identify the compiler ("gcc",
"gcc2", "clang"). Then we can refactor the related code in the jam build system. The current
approach, fixing the compilation while not even using a proper compilation environment, is just backward.
Yes, I very much agree that the current approach is only a hack. It's a hack so
that it's possible to at least build a Clang-only build. So I think we should
come up with 2 solution: One short-term solution and a long-term solution.
As the Jam system seems to be not so well-understood by many Haiku developers
and it seems you and Axel are the only ones who know enough about it / really
care about it, I would suggest that we 3 have a discussion on IRC so we can
talk through the different approaches and select the best one (we could even do
that in German then, to make things easier), as the problem seems to be more
complex than any of us thought at first. After that discussion, we could send
another mail to the list summarizing our decision to document it. Do you two
agree on that?
