llvm::SMDiagnostic::print breaks GNU readline

[osandov]

After printing an LLVM diagnostic message, the REPL doesn't work properly. This is because in asmaseDiagHandler(), we call llvm::SMDiagnostic::print(). This calls through llvm::raw_fd_ostream::has_colors(), llvm::sys::Process::FileDescriptorHasColors(), and finally terminalHasColors(). terminalHasColors() calls the ncurses setupterm() function, which apparently breaks GNU readline. I need to figure out a way to workaround or fix this.

[osandov]

Interesting that bcc also hit this in iovisor/bcc#615. The problem is actually the set_curterm((struct term *)nullptr). A possible fix for LLVM would be to only call setupterm() if cur_term != nullptr and not do the set_curterm()/del_curterm() dance at all.