Removed const modifier from LPInfo object on stack that was causing a…

[clarkse]

… warning from not being initialized properly.

[lucafedeli88]

Hi @clarkse ,
thank you for your contribution.
Could you please provide some more details on the configuration in which you saw a warning about this variable? In principle, the amrex::MLEBNodeFDLaplacian constructor takes info as a constant reference, so it should be OK to have const amrex::LPInfo info; here.

[clarkse]

This is the error I am getting building with GCC 9.4.0:

/home/st247c@HE.local/src/WarpX/Source/ablastr/fields/VectorPoissonSolver.H(133): warning #811-D: const variable "info" requires an initializer -- class "amrex::LPInfo" has no user-provided default constructor
const amrex::LPInfo info;

I checked in PoissonSolver.H and it appears that the const is not in front of the amrex::LPInfo instantiation in that case. I traced the addition of the const modifier to:
#3921

In this PR it was added to VectorPoissonSolver, but not PoissonSolver. I was just getting annoyed at seeing the compile time warning, so if we want to use the const then the default constructor for amrex::LPInfo should have a default constructor.

[clarkse]

@lucafedeli88 does this work for you? It appears consistent with usage in AMReX.

[lucafedeli88]

Looks OK to me. Thanks!