[tilasoldo]

Hi,

I'm having a very weird issue about compilation in OpenFoam 3&4, hope you guys can help me.

I'm developing my own turbulence model in OF and I have different results under Linux and Mac on the following line :

volScalarField F_wake = Foam::exp(-Foam::pow(Rew / 1e5, 2.0));

where Rew is a volScalarField. This code compile with no errors under Linux (Linux Mint 18), but under macOS 10.12 I get :

../turbulenceModels/lnInclude/sstTransitionBase.C:620:20: error: conversion from 'tmp<GeometricField<scalar, fvPatchField, Foam::volMesh> >' (aka 'tmp<GeometricField<double, fvPatchField, Foam::volMesh> >') to 'volScalarField'
      (aka 'GeometricField<double, fvPatchField, Foam::volMesh>') is ambiguous
    volScalarField F_wake = Foam::exp(-Foam::pow(Rew / 1e5, 2.0));
                   ^        ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
$WM_PROJECT_DIR/src/OpenFOAM/lnInclude/tmp.H:153:16: note: candidate function
        inline operator const T&() const;
               ^
$WM_PROJECT_DIR/src/OpenFOAM/lnInclude/GeometricField.H:374:9: note: candidate constructor
        GeometricField
        ^

I don't understand what is ambiguous in that, and most of all why it is ambiguous on Mac but not on Linux!
If I replace the F_wake definition by

volScalarField F_wake(Foam::exp(-Foam::pow(Rew / 1e5, 2.0)));

the problem disappear, but I'm not fully satisfied since I don't understand.

$ clang --version
Apple LLVM version 8.0.0 (clang-800.0.42.1)
Target: x86_64-apple-darwin16.1.0
Thread model: posix

[alexeym]

Hi,

Foam::exp(...) returns tmp<volScalarField>. So

volScalarField F_wake(Foam::exp(-Foam::pow(Rew / 1e5, 2.0)));

just invokes constructor from tmp<volScalarField> (http://cpp.openfoam.org/v4/a00931.ht...89f53565172607), no ambiguity; while behaviour of the code

volScalarField F_wake = Foam::exp(-Foam::pow(Rew / 1e5, 2.0));

is compiler-dependent (since it involves creation of temporary object). In case of clang it can not decide what you would like to use: constructor from tmp<...> or copy-constructor (http://cpp.openfoam.org/v4/a00931.ht...b4937af8da4bff), since tmp<T> can be converted to const T&.

Not sure if this behaviour is Mac-specific, guess, clang on Linux will also emit the error.

[tilasoldo]

Thank you for your quick reply, I understand better now

Have a nice day!