The data type should be GStatBuf, not struct stat.
The documentation of g_stat () (https://developer.gnome.org/glib/unstable/glib-File-Utilities.html#g-stat) states:
In Microsoft's compiler, by default struct stat means one with 64-bit time fields while in MinGW struct stat is the legacy one with 32-bit fields.
To hopefully clear up this messs, the gstdio.h header defines a type GStatBuf which is the appropriate struct type depending on the platform and/or compiler being used. On POSIX it is just struct stat, but note that even on POSIX platforms, stat() might be a macro.