Tip for that fork: For real-world usage, use -F compressed for it to generate compressed WIF private key format,
the uncompressed form (although valid) is already deprecated and will produce quite higher transaction input size than the former.
Yes, it's 10gic's forked version, since the original repo isn't maintained anymore, i used this instead. Thanks for the tip, I'll remember to use it when I run vanitygen++ again . I am still exploring new options.....
It's better to report it to its GitHub repository as a new issue.
I googled it a bit to understand what this error was. Looks like it's related to the OS not the program, not sure! Anyway, I'll report it, when i get the time.