[Soplex] Compilation error in soplex include file when building scip

[Leon Eifler]

Hi Peter,

thank you for your detailed bug report. I will make the suggested change 
and it will be part of the next bugfix release (and visible on github 
sooner).

Best regards,
Leon

Am 6/19/2023 um 10:03 PM schrieb Peter Notebaert:
> When I try to compile scip, I get a compilation error in a soplex 
> include file.
>
> I compile under windows with cmake and it uses Microsoft Visual Studio 
> 17 2022
>
> First I had to build soplex. I used following commands for that:
>
> cmake -Bbuild -H.
> cmake --build build --config Release
>
> This worked find and generated the soplex binaries.
>
> Then I use the following command to build scip:
>
> cmake -Bbuild -H. -DSOPLEX_DIR=..\soplex\build -DZLIB=off 
> -DREADLINE=off -DGMP=off -DPAPILO=off -DZIMPL=off -DIPOPT=off
>
> Which works fine. Then I use the following command to build:
>
> cmake --build build --config Release
>
> At a certain point it gives:
>
> C:\git\soplex\src\soplex/ssvectorbase.h(135,1): error C2445: result 
> type of conditional expression is ambiguous: types 'R' and 
> 'soplex::Real' can be converted to multiple common types 
> [C:\git\scip\build\src\libscip.vcxproj]
>           with
>           [
>               R=Rational
>           ]
> C:\git\soplex\src\soplex/ssvectorbase.h(135,1): message : could be 'R' 
> [C:\git\scip\build\src\libscip.vcxproj]
>           with
>           [
>               R=Rational
>           ]
> C:\git\soplex\src\soplex/ssvectorbase.h(135,1): message : or     
> 'soplex::Real' [C:\git\scip\build\src\libscip.vcxproj]
> C:\git\soplex\src\soplex/ssvectorbase.h(133,1): message : while 
> compiling class template member function 'R 
> soplex::SSVectorBase<R>::getEpsilon(void) const' 
> [C:\git\scip\build\src\libscip.vcxproj]
>           with
>           [
>               R=Rational
>           ]
> C:\git\soplex\src\soplex/ssvectorbase.h(861,16): message : see 
> reference to function template instantiation 'R 
> soplex::SSVectorBase<R>::getEpsilon(void) const' being compiled 
> [C:\git\scip\build\src\libscip.vcxproj]
>           with
>           [
>               R=Rational
>           ]
> C:\git\soplex\src\soplex/basevectors.h(898,55): message : see 
> reference to class template instantiation 'soplex::SSVectorBase<R>' 
> being compiled [C:\git\scip\build\src\libscip.vcxproj]
>           with
>           [
>               R=Rational
>           ]
>
> It's about this code:
>
>    R getEpsilon() const
>    {
>       assert(this->_tolerances != nullptr);
>       return this->_tolerances == nullptr ? R(0) : 
> this->tolerances()->epsilon();
>    }
>
> And specifically
>
> return this->_tolerances == nullptr ? R(0) : 
> this->tolerances()->epsilon();
>
> I guess most compilers accept an implicit cast from 
> this->tolerances()->epsilon() which is a soplex::Real and type R.
>
> To make it compile, I changed the line to:
>
> return this->_tolerances == nullptr ? R(0) : 
> (R)this->tolerances()->epsilon();
>
> And then everything compiles fine.
>
> My C++ knowledge is very limited (I never got further than C) so I am 
> also not 100% sure is this is the correct solution for this problem.
>
> It would be great if the code was changed to solve this ambiguity.
>
> Thank you,
>
> Peter Notebaert
>
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