Patch doesn't let me comment, but I believe to be strictly standards conformant, sigwinch_received should be declared as a `volatile sig_atomic_t`, not `char`. See: https://www.securecoding.cert.org/confluence/display/c/SIG31-C.+Do+not+access+shared+objects+in+signal+handlers

Also, to close an incredibly narrow race window, I believe sigwinch_received should be set to zero before calling rl_resize_terminal(), on the theory that otherwise, the signal could be received just after the call, but before setting the flag to 0, the signal handler would set it to 1, but we'd promptly squash that by setting it back to 0 (even though a resize occurred that should be handled).