[LLVMdev] clang++ on MacOSX with fsf-gcc libstdc++?

[Eli Friedman]

On Thu, Apr 12, 2012 at 10:44 AM, Andrea Bigagli <andrea.bigagli at me.com> wrote:
> Hi,
> the subject says it all...
>
> After some experimenting, I got a bit confused as far as what the proper
> thing to do might be....
>
> I build llvm/clang from trunk sources on OSX Lion 10.7.3 (i.e.
> x86_64-apple-darwin11.3.0 to speak GNU's platform-ese) where I also have
> successfully built a fsf-gcc 4.6.2 (and lately a 4.7 for that matter) from
> sources.
> Now, I think I understand that by playing with clang's
> lib/Frontend/InitHeaderSearch.cpp you can have clang use whatever libstdc++
> include files you want.
>
> Is that really true and fully supported practice, or do you have, when on
> OSX, either stick with Apple's (through Xcode-)provided gcc 4.2.1's
> libstdc++ or the all-new (but still a bit immature) libc++?
>
> I'm aware (after posting http://llvm.org/bugs/show_bug.cgi?id=12303) that if
> you build clang with paths tuned for, say, gcc-4.6's libstdc++, then you
> have to remember, every time you build something with clang++, to always
> make the linker find gcc-4.6's libstdc++, but as cumbersome as it might seem
> (if there's some configure hook that avoids the need of always passing
> "-L<wherever gcc-4.6'libstdc++ lives>" I'd really be happy to use it), it's
> always worked for me.
>
> Until lately, when I built the latest gcc-4.7 and since then clang++
> (rebuilt of course with paths updated for the new compiler) chokes on every
> cpp file as soon as I start including something like <iostream> or <vector>
> etc..
>
> Is it just a problem with gcc-4.7 libstdc++ headers that for some reason
> clang++ is not (yet) able to digest, or have I always been doing something
> not supported on OSX and I've just been lucky that it has been working until
> now?

There are known issues with using the libstdc++ 4.7 headers with
clang.  If you're interested in specifics, try searching
llvm.org/bugs/ .(Not that I would call the setup you're using on OSX
"supported", exactly, but there isn't any particular reason it
shouldn't work.)

On a side note, please file bugs if you're running into issues with libc++.

-Eli