[Libclc-dev] Question regarding change to configure.py

[Tom Stellard]

On Fri, Sep 06, 2013 at 10:13:31PM +0100, Jeroen Ketema wrote:
> 
> On Sep 6, 2013, at 10:01 PM, Tom Stellard <tom at stellard.net> wrote:
> 
> > On Wed, Sep 04, 2013 at 10:40:04PM +0100, Jeroen Ketema wrote:
> >> 
> >> Hi,
> >> 
> >> I've a question regarding commit c2bb4658f (configure: Fix build when clang is installed to a non-standard prefix).
> >> 
> >> I wonder if the change made in this commit is actually correct. My setup is as follows:
> >> 
> >> * The default compiler on my system is a clang/llvm 3.2 compiler
> >> 
> >> * I want to build libclc for a clang/llvm 3.3 compiler (which I built from source)
> >> 
> >> * The clang/llvm 3.3 compiler cannot use the default C++ library on my system (using it results in compile errors due to incompatibilities in the header files)
> >> 
> >> The change causes prepare-builtins to be built with the same compiler that libclc is being built for (by pointing to the correct llvm-config). However, now prepare-builtins doesn't build any longer, because the clang/llvm 3.3 compiler does not have access to a functioning C++ library. Hence, it seems that prepare-builtins should be built using the same compiler used to build clang/llvm 3.3 and not the clang/llvm 3.3 compiler, or am I mistaken?
> >> 
> > 
> > You should be able to build prepare-builtins with any compiler even gcc.
> > Your problem seems to me more like a configuration issue on your system
> > rather than a bug in the libclc configure script, but then again I don't
> > quite understand what problem you are having with clang.
> 
> After the commit mentioned above configure forces prepare-builtins to be build with the same clang that libclc is being built for. This clang(++) is incomplete on my system in as much that it doesn't have access to a C++ library. So, I would like to use the default C++ compiler on my system to build, which is was doing automatically before this commit (by accident you may argue :-) I hope this clarifies things?
> 

I think I get it, so basically your version of clang can compile cl but
not c++.

> Not sure what the solution here would be, I could add a flag to configure that overrides which C++ compiler is used to build prepare-builtins? Plus it should maybe pick the default C++ compiler as the default compiler to build prepare-builtins?

I think adding a configure flag for this is the best solution.

-Tom