SpatiaLite on Windows

Currently Wiki suggests downloading mod_spatialite directly from gaia-gis.

This is an outdated version of the library and depends on the MinGW C/C++ runtime which causes a problem with Windows 10.

This file comes from MinGW, the compiler they use to build the extension. Replacing it with a newer version works.

Delete libstdc++_64-6.dll from DB4S folder
Go to https://sourceforge.net/projects/mingw-w64/files/ and download one of x86_64-win32-seh files
Or use this direct link here
Extract it somewhere and look into the bin folder
Copy both libstdc++-6.dll and libgcc_s_seh-1.dll to DB4S folder
Rename libstdc++-6.dll to libstdc++_64-6.dll
Try to load the module again. This time it should work.

One could use the osgeo4w version which is compiled with MSVC (same as DB4S).
On Windows, DB4S comes with MSVC runtime and no additional runtime DLLs are needed.
Also osgeo4w version has more features embedded.

osgeo4w version can be obtained with osgeo4w online installer or downloaded directly from http://download.osgeo.org/osgeo4w

Their repo contains all necessary dependencies (also dev files if anyone needs them)

http://download.osgeo.org/osgeo4w/x86_64/release/spatialite/spatialite-4.3.0a-6.tar.bz2
http://download.osgeo.org/osgeo4w/x86_64/release/libxml2/libxml2-2.9.1-1.tar.bz2
http://download.osgeo.org/osgeo4w/x86_64/release/geos/geos-3.8.1-1.tar.bz2
http://download.osgeo.org/osgeo4w/x86_64/release/freexl/freexl-1.0.2-1.tar.bz2
http://download.osgeo.org/osgeo4w/x86_64/release/iconv/iconv-1.14-1.tar.bz2
http://download.osgeo.org/osgeo4w/x86_64/release/proj/proj-6.3.2-1.tar.bz2
http://download.osgeo.org/osgeo4w/x86_64/release/liblwgeom/liblwgeom-3.0.0-2.tar.bz2

Extract and copy mod_spatialite and dependencies to the DB4S binary directory.

Full list:

mod_spatialite.dll

freexl.dll
geos_c.dll
geos.dll
iconv.dll
libxml2.dll
lwgeom.dll
proj_6_3.dll

EDIT
libxml2.dll depends on MSVCR100.dll which should be shipped with Windows 10 by default
http://download.osgeo.org/osgeo4w/x86_64/release/msvcrt/msvcrt-1.0.3-1.tar.bz2