Add MSVC support and add __declspec to library interface

andeplane commented 7 years ago

Summary

To be able to use LAMMPS as a dll-library on windows, additional keywords like __declspec(export) and __declspec(import) to have these functions available. A few compilation issues with MSVC also need to be taken care of.

Type of Issue

Suggestion for an Enhancement

Detailed Description (Enhancement Suggestion)

I discussed this with @rbberger during the LAMMPS workshop. I want to create a Windows build of Atomify where LAMMPS is being used as a library. A typical way to create libraries on Windows is

#if COMPILING_DLL
    #define DLLEXPORT __declspec(dllexport)
#else
    #define DLLEXPORT __declspec(dllimport)
#endif

and use DLLEXPORT in front of the exported library functions. -DCOMPILING_DLL is used during compilation of the library. This part I could do myself, but there are other issues when compiling LAMMPS with MSVC compilers since

MSVS does not support variable-length arrays, and
there were some other compilation issues @rbberger mentioned that he needed to discuss with @sjplimp to pick a good way to solve them.

@rbberger can add more details on this.

rbberger commented 7 years ago

just for reference, I already have a branch (https://github.com/rbberger/lammps/commit/f6def26d16863ec004d0b27a79a6fc5c10660e84) with some quick hacks to make it "work". But I need to go over them and solve those issues properly / discuss with Steve or Axel.

akohlmey commented 3 years ago

@andeplane @rbberger been reviewing old issues today. Three comments:

variable length arrays have been (mostly) replaced with C++ standard conforming code
we have been building (and using) .dll files for Windows for a while now using CMake to build and the MinGW64 cross-compiler toolchain on Fedora. The precompiled Windows packages contain a LAMMPS executable that is basically just main.cpp and linked to liblammps.dll (same for lammps-shell), which in turn has been successfully imported and used into python on Windows using the Python distribution from python.org.
Ovito has a plugin loader that can load a (user provided) liblammps.dll (or liblammps.so) file for similar purposes.

Thus MSVC support is still not fully there. Due to lack of time and limited access to corresponding platforms, this will not be done quickly unless a dedicated developer can be found that will do the porting and support the port. I don't expect any updates to this outside of items that we have already planned anyway, so I am closing this now.

lammps / lammps