Hello Alex !
Thank you for your help.

To make my project LibRaw work (QT / Windows 10) with last release Libraw 0.21.2 and Unicode,
i added these 3 lines in the file libraw.h before compiling Librairy.

# define LIBRAW_WIN32_CALLS
# define __INTEL_COMPILER
# define LIBRAW_WIN32_UNICODEPATHS

May be one or two #define are required for my computer.
So i can open Raw file with a filename QString (16bits)

const wchar_t *array = (const wchar_t*)filename.utf16();
int ret = this->processor->open_file( array) ;
if( ret != LIBRAW_SUCCESS )
return false ;

Best regards,

Luciano