[cfe-dev] Clang 3.4 --with-gcc-toolchain question

[DbdM Tbt]

Good day Jon,

Thank you for the suggestion.
I rebuilt my llvm/clang with the additional '--with-extra-ld-options'
option but clang was still unable to find my gcc.
Perhaps the devtoolset-gcc-4.7 was installed in an unusual location and
explicitly adding the path is the only way?

One thing I tried was to modify clang/lib/Frontend/InitHeaderSearch.cpp.
I got the idea from an old thread:
  http://lists.cs.uiuc.edu/pipermail/cfe-dev/2012-April/021039.html
But still not ok. It was this thread that made me assume that the
--with-gcc-toolchain option was enough.
Looking for something else to go on, I tried to add some paths in the file
you mentioned, Toolchains.cpp.
Maybe there were some mistakes in my mod since the result was still not ok.
I will try again later.

There is another angle I have yet to try which is the procedure provided
here:
http://llvm.org/docs/GettingStarted.html#getting-a-modern-host-c-toolchain
Currently, I have problems compiling gcc 4.8.2 so I can't say yet what will
be the result.
Will try other versions.

Thank you very much for the support.

Best regards,
David



On Fri, May 9, 2014 at 3:17 AM, Jonathan Roelofs
<jonathan at codesourcery.com>wrote:

>  David,
>
> On my machine, gcc 4.7 is installed in /usr/local/tools/gcc-4.7.3
>
> I configure from a build directory:
> $ mkdir build && cd build
> $ ../llvm/configure --with-gcc-toolchain=/usr/local/tools/gcc-4.7.3
> --with-extra-ld-options=-Wl,-rpath,/usr/local/tools/gcc-4.7.3/lib/
> --enable-optimized
>
>
> On 5/8/14, 5:56 AM, DbdM Tbt wrote:
>
> Good day,
> I would like to ask about the behavior of '--with-gcc-toolchain'
> configuration option.
> I am currently trying out clang 3.4 with gcc 4.7 and for this, I used the
> centos devtools repo.
> GCC 4.7 is installed into /opt/centos/devtoolset-1.0/.
> I configured clang 3.4 like below:
> CC=/opt/centos/devtoolset-1.0/root/usr/bin/gcc
> CXX=/opt/centos/devtoolset-1.0/root/usr/bin/g++ <configure>
> --with-gcc-toolchain=/opt/centos/devtoolset-1.0/root/usr/
>
> Make is ok but when I try clang-check it doesn't seem to find 'iostream'.
> I thought with the option --with-gcc-toolchain, clang and its tools will
> automatically be pointed the gcc 4.7 directories.
> Perhaps I am missing something here or my assumptions are flawed. Can
> someone share some insights?.
>
> Using the -v option on clang-check, the "Selected GCC installation:" is
> blank and the list of include directories don't include the 4.7 directories.
>
> The GCCInsatllationDetector in clang/lib/Driver/ToolChains.h looks for
> crtbegin.o files in places like:
> /usr/local/tools/gcc-4.7.3/lib/gcc/<triple>/<major.minor.patch>/crtbegin.o
>
> In my case, that is:
>
> /usr/local/tools/gcc-4.7.3/lib/gcc/x86_64-unknown-linux-gnu/4.7.3/crtbegin.o
>
> But there are a bunch of formats for this kind of stuff. See
> Generic_GCC::GCCInstallationDetector::init in
> clang/lib/Driver/ToolChains.cpp (and the things that it calls).
>
> Cheers,
> Jon
>
> Explicitly specifying the include directories (-I option) in the
> clang-check invocation will work but is there another workaround?
> I would prefer to resolve such issues in the 'environment setup' aspect
> and not during 'application usage'.
>
> Thank you very much,
> David
>
>
>
> _______________________________________________
> cfe-dev mailing listcfe-dev at cs.uiuc.eduhttp://lists.cs.uiuc.edu/mailman/listinfo/cfe-dev
>
>
> --
> Jon Roelofsjonathan at codesourcery.com
> CodeSourcery / Mentor Embedded
>
>
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