[cfe-dev] Link error in clang but not g++

[Holger Brandsmeier]

Eli,

I managed to minimalize the error by taking out almost all the code
and removing all the dependencies to externa libraries. The final code
is in the attachment. This code produces the error for me.

There are now a few ways to remove the error.

1) Remove the second or third of those template instantiations in
quadraturePy.cpp:
template class QuadraturePy<double, 0>;
template class QuadraturePy<double, 1>;
template class QuadraturePy<int, 0>;

2) remove the second case here:
      case GAUSS_JACOBI: init<GAUSS_JACOBI>(dims);
      case GAUSS_LOBATTO: init<GAUSS_LOBATTO>(dims);

3) uncomment the line
//template class QuadratureRules<double, 0>; // CHECK: uncommenting
this line fixes the error

4) remove optimization (as mentioned in the previous mail)

Especially the case 3) seem to be a good lead. It might also be a bad
practise what I did there. I explicitly instantiate the class
QuadratureRulesPy
template class QuadratureRulesPy<double, 0>;
which then implicitly instantiates the symbol in the error
(parfem::QuadratureRules<double, 0>::QuadratureRules(unsigned int)).
But I do not explicitly instantiate the class QuadratureRules, which I
probably should have done.

The error is still quite strange with a symbol beeing undefined and
defined inside the same symbol, but with the approach 3) I am able to
solve this even for my big project.

-Holger


On Thu, Sep 15, 2011 at 00:33, Holger Brandsmeier
<holger.brandsmeier at sam.math.ethz.ch> wrote:
> Eli,
>
> it did not really matter much, how the constructor looks like. So I
> was able to shorten it very much and still keep the error, namely:
>
>  template<class ScalarT, int type>
>  QuadratureRules<ScalarT, type>::QuadratureRules(unsigned int n)
>  {
>    bool cond = (n >= 2);
>    if (!(cond)) {
>      std::stringstream errorMsg;
>      errorMsg << "by violating condition <n >= 2>";
>      throw std::logic_error(errorMsg.str());
>    }
>  }
>
> I can not shorten it much more, as otherwise the constructor is
> removed from the object file completely (I guess due to optimization).
> This is probably also bad by itself (the other file still references
> the optimized-out constructor!), but my current goal is to simplify
> the code as much as possible and still keep the error.
>
>> nm -C libintegration.so | grep "parfem::QuadratureRules<double, 0>::QuadratureRules"
>         U parfem::QuadratureRules<double, 0>::QuadratureRules(unsigned int)
> 0007b7b0 W parfem::QuadratureRules<double, 0>::QuadratureRules(unsigned int)
>
> I also notice that the error disappears if I turn of optimization. So
> the error is there if I use
> `clang -ferror-limit=2 -g -O2` [...]
> and also for -O3. Without any optimization the result is
>
>> nm -C libintegration.so | grep "parfem::QuadratureRules<double, 0>::QuadratureRules"
> 000d3ac0 W parfem::QuadratureRules<double,
> 0>::QuadratureRules(parfem::QuadratureRules<double, 0> const&)
> 000d2a70 W parfem::QuadratureRules<double, 0>::QuadratureRules(unsigned int)
> 000d3b30 W parfem::QuadratureRules<double,
> 0>::QuadratureRules(parfem::QuadratureRules<double, 0> const&)
> 000d2e10 W parfem::QuadratureRules<double, 0>::QuadratureRules(unsigned int)
>
> -Holger
>
> On Wed, Sep 14, 2011 at 23:46, Eli Friedman <eli.friedman at gmail.com> wrote:
>> On Wed, Sep 14, 2011 at 2:41 PM, Holger Brandsmeier
>> <holger.brandsmeier at sam.math.ethz.ch> wrote:
>>> On Wed, Sep 14, 2011 at 21:19, Eli Friedman <eli.friedman at gmail.com> wrote:
>>>> On Wed, Sep 14, 2011 at 12:15 PM, Holger Brandsmeier
>>>> <holger.brandsmeier at sam.math.ethz.ch> wrote:
>>>>> Eli,
>>>>>
>>>>> I tried to replace the linker with g++, but no success.
>>>>>
>>>>> Out of the three steps:
>>>>>  1) build quadratureRulesPy.cpp
>>>>>  2) quadraturePy.cpp
>>>>>  3) link
>>>>>
>>>>> I need to use g++ for step 1) (which creates the symbol
>>>>> parfem::QuadratureRules<double, 0>::QuadratureRules).
>>>>>
>>>>> I can then use clang for steps 2 and/or 3 which works nicely. If I use
>>>>> clang for step 1 then I always end up with the reported error.
>>>>
>>>> Hmm... it's possible clang is using the wrong linkage.
>>>>
>>>> Are you using clang from trunk?  If not, can you try?
>>>> (http://clang.llvm.org/get_started.html)
>>>>
>>>> -Eli
>>>>
>>>
>>> Eli,
>>>
>>> ok I downloaded it from the SVN and compiled it with the trunk version:
>>>
>>>> Debug+Asserts/bin/clang --version
>>> clang version 3.0 (trunk 139719)
>>> Target: i386-pc-linux-gnu
>>> Thread model: posix
>>>
>>> The error stays exactly the same (the compilation takes significantly
>>> longer as it is the debug version, but I guess that is to be
>>> expected).
>>
>> Okay... what exactly does the definition of
>> parfem::QuadratureRules<double, 0>::QuadratureRules look like?
>>
>> -Eli
>>
>
>
>
> --
> Holger Brandsmeier, SAM, ETH Zürich
> http://www.sam.math.ethz.ch/people/bholger
>



-- 
Holger Brandsmeier, SAM, ETH Zürich
http://www.sam.math.ethz.ch/people/bholger
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