MSVC compile error: MolHash scoped enum cannot be redeclared as unscoped

[mcs07]

In preparation for updating the conda-forge recipe, I just attempted to build RDKit on Windows using the Visual Studio compiler version that is used by conda-forge on Azure Pipelines (cmake says MSVC 19.0.24234.1, I believe this is from a VS2017 install with optional extra component VC++ 2015.3 v14).

I get the following error from the new MolHash code:

c:\anaconda\conda-bld\debug_1572451087860\work\code\graphmol\molhash\nmmolhash.h(45): error C3431: 'HashFunction': a scoped enumeration cannot be redeclared as an unscoped enumeration

The RDKit CI on Azure Pipelines (apparently using MSVC 19.16.27034.0) does not seem to have this problem, so I guess it is specific to the older version of the compiler.

Hopefully we could work around this with a patch in the conda-forge recipe? But I haven't been able to figure out how yet.

Configuration:

• RDKit Version: 2019.09.1
• Operating system: Windows

[greglandrum]

@mcs07: I can't test this at the moment, but you might try changing line 45 of nmmolhash.h to:

RDKIT_MOLHASH_EXPORT std::string MolHash(RWMol *mol, HashFunction func);

and line 683 of hashfunctions.cpp to:

std::string MolHash(RWMol *mol, HashFunction func) {

[greglandrum]

If that works, we can go ahead and make the change on master and fix this for v2019.09.2

[mcs07]

It works! I'll put in a PR to the conda-forge recipe with this as a temporary patch to update it to 2019.09.1.