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

[DbdM Tbt]

Good day to all,
Just an update, building clang with a gcc built from source seemed to work
fine. ('-v' option shows the correct gcc location).
Still not sure why my previous clang configuration/setup using a gcc
installed from the devtools repo won't work.
If someone would have some insights on possible causes, please feel free to
share.
For now I will go with this setup.
Thank you all,
David



On Fri, May 9, 2014 at 6:19 PM, DbdM Tbt <spin.x2k at gmail.com> wrote:

> 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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